gnss-sdr/docs/CHANGELOG.md

Changelog

All notable changes to GNSS-SDR will be documented in this file.

Unreleased

Improvements in Interoperability:

• Improved error handling in UDP connections.
• Make it possible to receive multiple constellations using a single channel wideband device (HackRF/LimeSDR/USRP). Demonstration: https://www.youtube.com/watch?v=ZQs2sFchJ6w https://www.youtube.com/watch?v=HnZkKj9a-QM

Improvements in Portability:

• Fix building against google-glog 0.7.x.
• Find dependencies in the loongarch64 architecture.
• Soft transition from GFlags and Google Logging (glog) to Abseil Logging and Flags libraries. While gflags and glog have dutifully served GNSS-SDR for over a decade, they are now showing signs of aging. The latest version of gflags dates back six years now, with its last commit in the master branch occurring two years ago. Glog remains well maintained, with its latest version v0.7.0 released in February 2024, but with no active development of new features and stuck at C++14. Abseil, on the other hand, represents a contemporary evolution in software development, supports C++17 and C++20, and has absorbed the functionalities of flags and logging from its predecessors. Furthermore, as Abseil has become a prerequisite for the latest versions of Protocol Buffers, its eventual inclusion in GNSS-SDR's indirect dependencies is inevitable. Leveraging Abseil allows for eliminating the need for gflags and glog, thereby reducing the number of mandatory dependencies for GNSS-SDR in forthcoming GNU/Linux distributions. For seamless integration, GNSS-SDR requires a quite recent minimum version of Abseil, v20240116. If an older version is detected, the library will not be utilized, and GNSS-SDR will fall back to using gflags and glog, which still can be used and are fully supported. A new CMake configuration option -DENABLE_GLOG_AND_GFLAGS=ON is available to force the usage of glog and gflags instead of Abseil, even if a valid version of that library is present. If the Abseil version installed in your system is too old but you still want to try it, you can also force the downloading and building of a recent version with the new CMake configuration flag -DENABLE_OWN_ABSEIL=ON (requires CMake >= 3.24, otherwise it has no effect). This change has a downside in maintainability, since the source code becomes plagued with preprocessor directives required to maintain compatibility both with gflags and glog, and with Abseil.
• Historically, GNSS-SDR linked against the GnuTLS library for cryptographic functions. If GnuTLS was not found, then the building system looked for and linked against OpenSSL as a fallback. This was due to the OpenSSL 1.x dual license scheme, which was incompatible with GPL v3.0 license, preventing it from being a mandatory dependency for GNSS-SDR in most GNU/Linux distributions. This issue was solved with the release of OpenSSL 3.0.0, which transitioned to the Apache License 2.0, fully compatible with GPL v3.0. Accordingly, the GNSS-SDR building system now looks for OpenSSL in the first place and, if not found, then it looks for GnuTLS as a fallback.

Improvements in Usability:

• Tidy up the conf/ folder.

See the definitions of concepts and metrics at https://gnss-sdr.org/design-forces/

 

GNSS-SDR v0.0.19.1 - 2024-01-26

• Fix formatting of the CITATION.cff file.

GNSS-SDR v0.0.19 - 2024-01-23

Improvements in Efficiency:

• Fixed some performance inefficiencies detected by Coverity Scan.

Improvements in Interoperability:

• Added a new PVT configuration boolean flag (flag_geohash_log_out) that enables or disables the Position Geohash tag output in INFO log files. Set to false by default.
• New fields have been added to the custom output stream defined by monitor_pvt.proto:
  • utc_time (a RFC 3339 datetime string),
  • velocity in the local ENU frame (vel_e, vel_n, and vel_u), in m/s,
  • the course over ground, cog, in degrees,
  • the status of the Galileo's High Accuracy Service, galhas_status:
    • 0: HAS data not available
    • 1: HAS Corrections applied
  • geohash, an encoded geographic location.

Improvements in Maintainability

• Removed useless casts and shadowed variables, improving source code readability.

Improvements in Portability:

• Updated local cpu_features library to v0.9.0.
• volk_gnsssdr: fix syntax for Python 3.12 without breaking backward compatibility with Python 2.7.
• Fixed linking against GNU Radio v3.10.9.1.
• Make use of new API if linking against VOLK >= 3.1.
• Fixed undefined behaviour in volk_gnsssdr arising from incompatibility between complex numbers in C and C++.
• Now build system paths are not leaked when cross-compiling.
• Enabled building using macOS Sonoma and arm64 processor architecture.

Improvements in Repeatability:

• A Kalman filter is now available in the PVT block, smoothing the outputs of a simple Least Squares solution and improving the precision of delivered fixes. It can be enabled by setting PVT.enable_pvt_kf=true in the configuration file. The user can set values for the measurement and process noise covariances with the following optional parameters (here with their default values): PVT.kf_measures_ecef_pos_sd_m=1.0, in [m]; PVT.kf_measures_ecef_vel_sd_ms=0.1, in [m/s]; PVT.kf_system_ecef_pos_sd_m=2.0, in [m]; and PVT.kf_system_ecef_vel_sd_ms=0.5, in [m/s].

Improvements in Scalability:

• Fixed some potential data race conditions detected by Coverity Scan.

Improvements in Usability:

• The Galileo E1B Reduced CED parameters usage has been set to false by default. You can activate its usage with Galileo_E1B_Telemetry_Decoder=true in your configuration file.
• The generation of Galileo E6B observables has been disabled if the user sets PVT.use_e6_for_pvt=false, fixing the PVT computation in some multi-band configurations.
• Fix bug in the custom binary output (PVT.enable_monitor=true) output rate. Before this fix, it was outputting data every 20 ms, instead of observing the PVT.output_rate_ms setting.
• Now the program exits properly if a SIGINT signal is received (e.g., the user pressing Ctrl+C, or another user application sending an interruption signal).
• The estimated CN0 value is now printed in the terminal when navigation data is succesfully decoded.
• Fixed GPS navigation message satellite validation.
• Latitude and longitude are now reported in the terminal with six decimal places (the sixth decimal place worths up to 0.11 m), instead of the overkilling nine (the ninth decimal place worths up to 110 microns). Similarly, height in meters is now reported with two decimal places instead of three, and velocity in m/s also with two decimal places instead of three.
• Fixed the rate at which KML, GPX, GeoJSON, and NMEA annotations are made. The rate is now set by PVT.output_rate_ms (500 ms by default), and can be particularized by PVT.kml_rate_ms, PVT.gpx_rate_ms, PVT.geojson_rate_ms, and PVT.nmea_rate_ms. Those values should be multiples of PVT.output_rate_ms, or the least common multiple will be taken.

See the definitions of concepts and metrics at https://gnss-sdr.org/design-forces/

 

GNSS-SDR v0.0.18 - 2023-04-06

Improvements in Accuracy:

• Processing and application of the corrections provided by the Galileo High Accuracy Service (HAS) to the PVT solution. It requires at least a Galileo E1 (or E5a) + Galileo E6B configuration. A new configuration parameter PVT.use_has_corrections, set to true by default, can be used to deactivate the application of HAS corrections but still retrieve the HAS data if set to false.

Improvements in Availability:

• Fixed bug that made the PVT block to not resolve position anymore after a loss of samples event.
• Improved non-coherent acquisition when Acquisition_XX.blocking=false.
• Implemented processing of BeiDou PRN 34 up to PRN 63 signals.
• Implemented Hamming code correction for Glonass navigation message.
• Now the first iteration of the PVT computation is initialized by the Bancroft method. This allows to get PVT fixes in some unusual geometries (e.g., GNSS-like signals transmitted by LEO satellites). This initialization is performed by default. You can opt-out by setting PVT.bancroft_init=false in your configuration file.

Improvements in Interoperability:

• Enabled PVT computation in the Galileo E5a + E5b receiver. Observables reported in the RINEX file.
• Fixed PVT computation in the Galileo E5b-only receiver.
• Get E6B observables and PVT solutions in the Galileo E1B + E6B receiver. Decoding of HAS messages as described in the HAS SIS ICD v1.0. Generation of RTCM 3.2 messages from the received HAS messages in the IGS State Space Representation (SSR) Format. Specifically, it generates messages of type IGM01 (SSR Orbit Correction), IGM02 (SSR Clock Correction), IGM03 (SSR Combined Orbit and Clock Correction), and IGM05 (SSR Code Bias).
• Added a ZMQ_Signal_Source for working with streams of samples published via ZeroMQ.
• Fixed register unpacking for Labsat3W files in Labsat_Signal_Source. This fix is only available if gnss-sdr is linked against Boost >= 1.58.0.

Improvements in Maintainability:

• The now archived GPSTk toolkit, used in some optional tests and applications, has been replaced by the new GNSSTk C++ Library. Compatibility with the former GPSTk toolkit is maintained.

Improvements in Portability:

• Improved detection of the BLAS library under macOS / Macports (the lapack port dependency installed with the +openblas variant does not install blas but openblas, which is used as a replacement if blas is not found).
• Removed duplicated files in the Secure User Plane Location implementation, which caused issues when linking with some compilers.
• Added support for Xilinx's Zynq UltraScale+ devices (requires the -DENABLE_FPGA=ON building option).
• Fixed running time error if the gnss-sdr binary and/or the GNU Radio libraries were built with the -D_GLIBCXX_ASSERTIONS compiler option. This is added by default in some GNU/Linux distributions (e.g., ArchLinux and Fedora).
• Fixed linking against libunwind when the glog library is built locally.
• The configuration options at building time -DENABLE_OWN_GLOG, -DENABLE_OWN_ARMADILLO, and -DENABLE_OWN_GNSSTK can now be switched ON and OFF without the need to start from an empty buiding folder.
• Improved CMake handling of the spdlog library used by GNU Radio >= 3.10.
• Make use of the C++20 standard if the environment allows for it.
• Improved passing of compiler flags to volk_gnsssdr if the corresponding environment variables are defined. This fixes warnings in some packaging systems.
• Improved support for the RISC-V architecture.
• Test files are now donwloaded at configuration time instead of being included in the source tree. This allows for a smaller package and fixes Lintian very-long-line-length-in-source-file warnings since those files were not recognized as binaries. The configuration flag -DENABLE_PACKAGING=ON passed to CMake deactivates file downloading.
• The ENABLE_GENERIC_ARCH building option was removed, simplifying the process of buiding the software in non-x86 processor architectures.
• If the Protocol Buffers dependency is not found, it is downloaded, built and statically linked at buiding time. If CMake >= 3.13 and the Abseil C++ libraries >= 20230117 are installed on your system, Protocol Buffers v22.2 will be used. If those requirements are not met, Protocol Buffers v21.4 will be used instead (requires autotools).
• Since Debian 8 "Jessie", which enjoyed Long Term Support until the end of June 2020, is not anymore in the Debian official repositories, we drop its support.
• Fixes for GCC 13 and Clang 16.

Improvements in Usability:

• Fixed large GLONASS velocity errors and the extended correlator when using the GLONASS_L1_CA_DLL_PLL_C_Aid_Tracking and GLONASS_L2_CA_DLL_PLL_C_Aid_Tracking implementations.
• The UHD_Signal_Source learned a new parameter otw_format for setting the over-the-wire data format (that is, the format used between the device and the UHD) in some devices, thus allowing to select the sc8 format instead of the default sc16. This would reduce the dynamic range and increase quantization noise, but also reduce the load on the data link and thus allow more bandwidth.
• The UHD_Signal_Source learned another two optional parameters: device_recv_frame_size and device_num_recv_frames for overriding transport layer defaults.
• Added gain setting and reading for the XTRX board when using the Osmosdr_Signal_Source implementation of a SignalSource.
• The Osmosdr_Signal_Source implementation learned a new parameter if_bw to manually set the bandwidth of the bandpass filter on the radio frontend.
• The new configuration parameter Channels_XX.RF_channel_ID allows to specify the signal source per channel group.
• New configuration parameter PVT.use_unhealthy_sats, set by default to false, allows processing observables of satellites that report an unhealthy status in the navigation message if set to true.
• Added the Geohash of the PVT solution in the internal logs.
• Allowed the CMake project to be a sub-project.

See the definitions of concepts and metrics at https://gnss-sdr.org/design-forces/

 

GNSS-SDR v0.0.17 - 2022-04-20

Improvements in Availability:

• Compute PVT solutions when using GPS L5 signals even if the satellite is reported as not healthy in the CNAV message.

Improvements in Portability:

• Updated cpu_features library to v0.7.0. The building option ENABLE_OWN_CPUFEATURES has been replaced by ENABLE_CPUFEATURES, defaulting to ON.
• Fixed building against GNU Radio v3.10.2.0.

Improvements in Reliability:

• Fix some defects detected by Coverity Scan 2021.12.1.

Improvements in Usability:

• Added a script at src/utils/scripts/download-galileo-almanac.sh that downloads an XML file with the latest Galileo almanac published by the European GNSS Service Centre at https://www.gsc-europa.eu/gsc-products/almanac

See the definitions of concepts and metrics at https://gnss-sdr.org/design-forces/

 

GNSS-SDR v0.0.16 - 2022-02-15

Improvements in Availability:

• Added the Galileo E5b receiving chain. The software is now able to compute PVT solutions as a standalone Galileo E5b receiver.
• Improved Time-To-First-Fix when using GPS L1 C/A signals, fixing a bug that was making the receiver to drop the satellite if the PLL got locked at 180 degrees, and making some optimizations on bit transition detection.
• Fixed a bug that prevented from obtaining PVT fixes with Galileo E1 OS signals if the I/NAV subframe type 0 was the first decoded subframe.

Improvements in Interoperability:

• Fixed setting of the signal source gain if the AGC is enabled when using the AD9361 front-end.
• Fixed the regeneration of Galileo ephemeris from the reduced clock and ephemeris data (CED) defined in the Galileo E1B INAV message introduced in Galileo OS SIS ICD Issue 2.0.
• Added a Limesdr_Signal_Source for interoperability with LimeSDR (requires gr-limesdr and the -DENABLE_LIMESDR=ON building flag).

Improvements in Maintainability:

• Rewritten Viterbi decoder for Galileo navigation messages. Encapsulated in a class instead of being implemented as free inline functions. This improves memory management and source code readability.
• Prefer initialization to assignment in constructors. This improves the readability of the code, could potentially increase performance, and allows for easier detection of unused data members (see the CppCoreGuidelines). Added the cppcoreguidelines-prefer-member-initializer clang-tidy check to enforce this policy.
• Non-functional change: Fixed formatting defects detected by clang-format 13.0.
• Non-functional change: Simplified flow graph disconnection.
• Updated GSL implementation to v0.40.0. See the gsl-lite release.
• CI - cpplint job on GitHub: Added the build/include_what_you_use filter for early detection of missing includes.
• CI - clang-tidy job on GitHub: More robust detection of LLVM paths installed by homebrew.

Improvements in Portability:

• Fixed building against the new API in the gr-iio component present in GNU Radio v3.10.X.Y.
• Fixed building against GNU Radio v3.10.X.Y, which does not support the C++20 standard.
• Fixed building against GNU Radio v3.10.X.Y, which replaced log4cpp by the spdlog and fmt libraries.
• Updated cpu_features library for improved processor detection.

Improvements in Reliability:

• Fixed some potential buffer overflows.
• Avoid source code lines longer than 512 characters. This was a warning raised by Lintian (very-long-line-length-in-source-file). Long lines in source code could be used to obfuscate the source code and to hide stuff like backdoors or security problems.

Improvements in Usability:

• Added a new monitor to extract the decoded data bits of the navigation messages and send them elsewhere via UDP. Activated by setting NavDataMonitor.enable_monitor=true, NavDataMonitor.client_addresses=127.0.0.1 and NavDataMonitor.port=1237 in the configuration file. Format described in the nav_message.proto file. A simple listener application written in C++ is included in src/utils/nav-listener as an example.
• Extract successful rate of the CRC check in the decoding of navigation messages. This can be enabled by setting TelemetryDecoder_XX.dump_crc_stats=true and, optionally, TelemetryDecoder_XX.dump_crc_stats_filename=./crc_stats in the configuration file. At the end of the processing (or exiting with q + [Enter]), the CRC check success rate will be reported in a file.
• The UHD_Signal_Source learned to dump data in folders that do not exist, e.g., if SignalSource.dump=true, SignalSource.dump_filename=./non-existing/data.dat, and the non-existing folder does not exist, it will be created if the running user has writing permissions. This also works for absolute paths.
• Added a new configuration parameter PVT.rtk_trace_level that sets the logging verbosity level of the RTKLIB library.
• Added a new output parameter Flag_PLL_180_deg_phase_locked in the monitor output that indicates if the PLL got locked at 180 degrees, so the symbol sign is reversed.
• Fixed a bug in the satellite selection algorithm for configurations with a large number of channels. The maximum number of channels per signal is now limited to the number of available satellites per system minus one. The number of channels performing concurrent acquisition, Channels.in_acquisition, cannot be larger than the total number of channels. The program will stop if those requirements are not met in the configuration file.
• Fixed program termination when using File_Signal_Source and extended integration times.
• The Fifo_Signal_Source Signal Source implementation learned to handle the ibyte type.
• Added a CITATION.cff file.
• Updated version of the Contributor Covenant to version 2.1.

See the definitions of concepts and metrics at https://gnss-sdr.org/design-forces/

 

GNSS-SDR v0.0.15 - 2021-08-23

Improvements in Availability:

• Added the reading of reduced clock and ephemeris data (CED) in the Galileo E1B INAV message introduced in Galileo OS SIS ICD Issue 2.0. If the reduced CED is available before the full ephemeris set, it is used for PVT computation until the full set has not yet been received. This can contribute to shortening the Time-To-First-Fix. Still experimental.
• Added the exploitation of the FEC2 Erasure Correction in the Galileo E1B INAV message introduced in Galileo OS SIS ICD Issue 2.0. This can contribute to shortening the Time-To-First-Fix. Since the added computational cost could break some real-time configurations, this feature is disabled by default. It can be activated from the configuration file by adding TelemetryDecoder_1B.enable_reed_solomon=true.
• Reduction of the TTFF in GPS L1 and Galileo E1 by improving the frame synchronization mechanism.

Improvements in Maintainability:

• The Contributor License Agreement (CLA) signing for new contributors has been replaced by a Developer's Certificate of Origin (DCO), which implies that contributed commits in a pull request need to be signed as a manifestation that contributors have the right to submit their work under the open source license indicated in the contributed file(s) (instead of asking them to sign the CLA document).
• Improved handling of changes in GNU Radio 3.9 FFT API.
• Improved handling of the filesystem library.
• Added an abstract class SignalSourceInterface and a common base class SignalSourceBase, which allow removing a lot of duplicated code in Signal Source blocks, and further abstract file-based interfaces behind them.
• Do not apply clang-tidy fixes to protobuf-generated headers.
• Refactored private implementation of flow graph connection and disconnection for improved source code readability.
• Added a base class for GNSS ephemeris, saving some duplicated code and providing a common nomenclature for ephemeris' parameters. New generated XML files make use of the new parameters' names.
• Update GSL implementation to 0.38.1. See https://github.com/gsl-lite/gsl-lite/releases/tag/v0.38.1
• Update references to the latest GPS ICDs (IS-GPS-200M, IS-GPS-800H, IS-GPS-705H) published in May, 2021.

Improvements in Portability:

• Avoid collision of the cpu_features library when installing the volk_gnsssdr library on its own, and VOLK has already installed its version. Added a new building option ENABLE_OWN_CPUFEATURES, defaulting to ON when building gnss-sdr but defaulting to OFF when building a stand-alone version of volk_gnsssdr. When this building option is set to ON, it forces the building of the local version of the cpu_features library, regardless of whether it is already installed or not.
• CMake's <policy_max> version bumped to 3.21. The minimum CMake version is 2.8.12.
• Fix building when using the Xcode generator, Xcode >= 12 and CMake >= 3.19.
• Fix building of FPGA blocks when linking against GNU Radio >= 3.9 and/or Boost >= 1.74.
• Fix linking of the <filesystem> library when using GCC 8.x and GNU Radio >= 3.8.
• If the Matio library is not found, now it is configured and built by CMake instead of using autotools.
• Added support for Apple M1 AArch64 architecture processor and for FreeBSD on x86, improved AMD microarchitecture detection.
• CMake now selects the C++23 standard if the environment allows for it.
• Improved detection of Gnuplot and gnss_sim when cross-compiling.
• NEON kernel implementations of the volk_gnsssdr library are now enabled in aarch64 architectures.

Improvements in Reliability

• Bug fix in the Galileo E1/E5 telemetry decoder that produced incorrect timing information if a satellite is lost and then readquired.
• Check satellites' health status. If a satellite is marked as not healthy in its navigation message, the corresponding observables are not used for navigation.

Improvements in Usability:

• Added a new Fifo_Signal_Source implementation that allows using a Unix FIFO as a signal source, thus allowing to multiplex signal streams outside of gnss-sdr, letting another program hold access to the receiver, or allowing signal sources that are not supported by gnss-sdr but can dump the signal to a FIFO.
• Avoid segmentation faults in the flow graph connection and/or starting due to some common inconsistencies in the configuration file.
• Provide hints to the user in case of failed flow graph connection due to inconsistencies in the configuration file.
• Fix segmentation fault if the RINEX output was disabled.
• Added a feature that optionally enables the remote monitoring of GPS and Galileo ephemeris using UDP and Protocol Buffers.
• Now building the software passing the -DENABLE_FPGA=ON to CMake does not make the receiver unusable when running on non-FPGA-enabled platforms. On FPGA-enabled platforms, now it is possible to run non-FPGA-enabled configurations.
• Fix bug that made the Monitor block to always set to 0 the carrier_phase_rads parameter value.
• The Labsat_Signal_Source implementation of the SignalSource block now can read files in the LabSat 3 Wideband format (.LS3W). When using this format, this source block can provide multiple RF chain outputs.
• Replace Receiver.sources_count configuration parameter name by GNSS-SDR.num_sources. The former parameter name is still read to ensure backward compatibility with configuration files using that nomenclature.
• Fix bug in searching for gr-iio when CMake was re-run several times with different settings for the -DENABLE_FMCOMMS2 or -DENABLE_PLUTOSDR building options.
• Fix building when using UHD >= v4.0.0.0.
• Fix building for -DENABLE_FMCOMMS2=ON and/or -DENABLE_PLUTOSDR=ON when the built-in gr-iio module introduced in GNU Radio 3.10 is found. This in-tree GNU Radio module takes precedence over the gr-iio package provided at https://github.com/analogdevicesinc/gr-iio. If the GNU Radio module is found, the other one is ignored.
• File changelog.md renamed to the more usual CHANGELOG.md uppercase name.
• New global configuration parameter GNSS-SDR.observable_interval_ms, set by default to 20 [ms], allows to control the internal rate at which computed observables sets are processed (50 observables sets per second by default).
• Fix bug in the Monitor.decimation_factor parameter, which was not working properly for other values than 1.

See the definitions of concepts and metrics at https://gnss-sdr.org/design-forces/

 

GNSS-SDR v0.0.14 - 2021-01-08

Improvements in Availability:

• Fixed bug in acquisition detection when the configuration parameter Acquisition_XX.threshold was set but Acquisition_XX.pfa was not, causing false locks.
• Fixed anti-jamming filters: Pulse_Blanking_Filter, Notch_Filter, and Notch_Filter_Lite.

Improvements in Efficiency:

• Faster SignalConditioner block when its implementation is set to Pass_Through.

Improvements in Interoperability:

• Added the Galileo E6 B/C signal structure based on E6-B/C Codes Technical Note, Issue 1, January 2019, including Acquisition and Tracking blocks. The Telemetry Decoder is still empty (only the CRC is checked, based on Galileo High Accuracy Service E6-B Signal-In-Space Message Specification v1.2, April 2020).

Improvements in Maintainability:

• Added a common shared pointer definition gnss_shared_ptr, which allows handling the boost::shared_ptr to std::shared_ptr transition in GNU Radio 3.9 API more nicely.
• Support new FFT and firdes blocks' API in GNU Radio 3.9.
• Added detection of inconsistent function prototypes in volk_gnsssdr library kernels at compile time.
• Fixed defects detected by clang-tidy check bugprone-reserved-identifier, and added to the checks list. This check corresponds to CERT C Coding Standard rule DCL37-C as well as its C++ counterpart, DCL51-CPP.
• Applied and added more clang-tidy checks related to readability: readability-make-member-function-const and readability-qualified-auto.

Improvements in Portability:

• Fixed -DENABLE_OWN_GLOG=ON building option when gflags is installed and it is older than v2.1.2 (e.g., in CentOS 7).
• Improved handling of old gflags versions, minimum version set to 2.1.2. Replaced google:: by gflags:: namespace when using functions of the gflags library.
• Replaced git:// by https:// as the used protocol when downloading Gflags, so it can work through firewalls requiring authentication.
• Fixed static linking of the matio library when downloaded and built by CMake.
• Improved CPU feature detection by switching to Google's cpu_features library: The volk_gnsssdr library had its own CPU feature detection methods, which were not totally reliable and difficult to implement across compilers and OSes. This is now handled by the cpu_features library, thus building upon that expertise. Since that library has higher dependency version requirements than GNSS-SDR, the old method is still used in old development environments. No extra dependency is needed. This change is transparent to the user, since everything is managed by the CMake scripts.
• The volk_gnsssdr library can be built on Microsoft Windows and can execute SIMD instructions on that OS.
• Removed all instances of _mm256_zeroupper() in the volk_gnsssdr library, since they are not required and lead to miscompilation with GCC 10.2 and optimization level -O3.
• Fixed building with -DENABLE_CUDA=ON for blocks implemented with CUDA.
• Fixed linking against the ORC library if it is present in the system.
• Fixed a bug introduced in v0.0.13 that prevented getting Galileo-only PVT fixes in some environments.
• Fixed duplication of protobuf build tree if it was locally built and then installed with DESTDIR variable set.

Improvements in Usability:

• Fixed a bug when enabling pseudorange carrier smoothing in other bands than L1.
• If SignalConditioner.implementation=Pass_Through, then all the configuration parameters for the DataTypeAdapter, InputFilter and Resampler blocks are ignored. This was the default behavior in GNSS-SDR v0.0.12, but it changed in v0.0.13. This change recovers the old behavior.
• Fixed occasional segmentation fault when exiting with q + [Enter] keys if Acquisition_XX.blocking=false.
• Fixed the termination of the receiver with q + [Enter] keys when using the Osmosdr_Signal_Source implementation of the SignalSource block.
• The Labsat_Signal_Source implementation of the SignalSource block now can be throttled with the new parameters SignalSource.enable_throttle_control and SignalSource.throttle_frequency_sps, thus allowing the emulation of real-time operation.
• Improved General Block diagram, both in content and in image resolution.
• The Custom_UDP_Signal_Source implementation now accepts SignalSource.sample_type=cfloat, in addition to the existing 4 and 8-bit length sample types.
• Fixed the obsdiff and rinex2assist utilities when installed if they were built with a locally downloaded version of GPSTk.
• The generated HTML documentation now makes use of the Doxygen grouping feature.
• Improved rendering of equations in HTML documentation generated by Doxygen. Make use of MathJax for equation rendering. Added new building option ENABLE_EXTERNAL_MATHJAX, set to ON by default. If set to OFF, it allows using a local installation of MathJax 2.
• Improved dumps in Telemetry Decoding blocks. Now they include the raw navigation message bits. If TelemetryDecoder_XX.dump=true, the resulting .dat binary file is also delivered in .mat format, which is readable from Matlab and Python.

See the definitions of concepts and metrics at https://gnss-sdr.org/design-forces/

 

GNSS-SDR v0.0.13 - 2020-07-29

Improvements in Efficiency:

• Faster internal handling of Gnss_Synchro objects by reducing the amount of copying via adding noexcept move constructor and move assignment operators, so the move semantics are also used in STL containers.
• All std::endl have been replaced by the '\n' character, since there is no need to always flush the stream.
• Performed a stack reordering of class members that seems to offer statistically better performance in some processor architectures and/or compilers.
• Add building option ENABLE_STRIP to generate stripped binaries (that is, without debugging symbols), smaller in size and potentially providing better performance than non-stripped counterparts. Only for GCC in Release build mode. Set to OFF by default.

Improvements in Maintainability:

• Improved usage of smart pointers to better express ownership of resources.
• Add definition of std::make_unique for buildings with C++11, and make use of it through the source code.
• Private members in headers have been sorted by type and size, minimizing padding space in the stack and making the files more readable for humans.
• Simpler, less error-prone design of the GNSSBlockFactory class public API and internal implementation.
• Simpler API for the Pvt_Solution class.
• Improved system constant definition headers, numerical values are only written once.
• Improved const correctness.
• The software can now be built against the GNU Radio 3.9 API that uses standard library's smart pointers instead of Boost's. Minimum GNU Radio required version still remains at 3.7.3.
• The software can now be built against Boost <= 1.73 (minimum version: 1.53).
• Fixed building with GCC 10 (gcc-10 and above flipped a default from -fcommon to -fno-common, causing an error due to multiple defined lambda functions).
• Fixed warnings raised by GCC 10 and Clang 10.
• Various improvements in the CMake scripts: better decision on the C++ standard to use; simplifications for various API dependency and environment versions requirements, with more intuitive naming for variables; fixed the ENABLE_CLANG_TIDY option; better GFORTRAN module; and broader adoption of the modern per-target approach.

Improvements in Portability:

• The software can now be cross-compiled on Petalinux environments.
• Removed python six module as a dependency if using Python 3.x.
• Make use of std::span if the compiler supports it, and use gsl-lite as a fallback. The latter has been updated to version 0.37.0.
• Improved finding of libgfortran in openSUSE and Fedora distributions.
• Improved interface for FPGA off-loading.
• Allow a random name for the build type. If not recognized, it is set to None. This allows packaging in some distributions that pass an arbitrary name as the build type (e.g., Gentoo) to avoid unexpected compiler flags. The building option ENABLE_PACKAGING must be set to ON when packaging.
• Do not stop the receiver if SysV message queues cannot be created.

Improvements in Reliability:

• Fixed a bug in GLONASS GNAV CRC computation.
• Fixed a bug in GLONASS time year.
• Fixed a possible buffer overflow in the generation of RTCM messages.
• Fixed bugs which could cause a random crash on receiver stopping.

Improvements in Reproducibility:

• Improved reproducibility of the volk_gnsssdr library: Drop compile-time CPU detection.

Improvements in Testability:

• Add building option ENABLE_BENCHMARKS, which activates the building of benchmarks for some code snippets, making it easier to developers to benchmark different implementations for the same purpose. Set to OFF by default.

Improvements in Usability:

• Do not pollute the source directory if the software is built from an out-of-source-tree directory. Downloaded external sources and test raw files are now stored in a ./thirdparty folder under the building directory. In the case of an out-of-source-tree build, the generated binaries are stored in an ./install folder, also under the building directory. The old behavior for generated binaries is maintained if the building is done from any source tree subfolder (for instance, gnss-sdr/build): in that case, binaries are stored in the source tree (under gnss-sdr/install).
• Defined new GNSS-SDR.GPS_banned_prns, GNSS-SDR.Galileo_banned_prns, GNSS-SDR.Glonass_banned_prns and GNSS-SDR.Beidou_banned_prns configuration parameters. The user can specify lists of satellites that will not be processed (e.g., GNSS-SDR.Galileo_banned_prns=14,18 since Galileo E14 and E18 satellites are not usable for PVT). Satellites on those lists will never be assigned to a processing channel.
• Added acquisition and tracking monitors, with configuration examples.
• Added a Matlab script to quantize the input signal with a given number of bits per sample.
• Fixed the building option -DENABLE_LOG=OFF, which strips internal logging from the binary and can help to reduce its size and ultimately to speed up the receiver. In binaries with enabled logging, it still can be disabled by passing the command line flag --minloglevel=3 to gnss-sdr. This can be relevant in embedded devices with scarce storage capabilities.
• Fixed a bug in the Signal Sources configuration that made the number of samples parameter ignored when too large (that is, when set larger than 2^31-1). Now the samples parameter accepts values up to 2^64-1, that is, 18,446,744,073,709,551,615 samples.
• Fixed a bug in the forwarding of NMEA messages to a serial port (configuration of the PVT.nmea_dump_devname parameter was ignored).
• Updated version of the Contributor Covenant to version 2.0. Added badge in the README.md file.

See the definitions of concepts and metrics at https://gnss-sdr.org/design-forces/

 

GNSS-SDR v0.0.12 - 2020-03-13

Improvements in Accuracy:

• Improved accuracy of the C/N0 estimator.

Improvements in Availability:

• Fixed computation of acquisition threshold when using the Acquisition_XX.pfa configuration parameter, including non-coherent accumulation (Acquisition_XX.max_dwells > 1).

Improvements in Efficiency:

• Faster implementation of the Viterbi decoder for Galileo navigation messages.
• The -O3 flag is now passed to GCC in Release and RelWithDebInfo build types (instead of -O2), thus enabling tree vectorization. Disabled if building for Fedora or Gentoo.

Improvements in Flexibility:

• New Tracking parameters allow the configuration of the C/N0 and lock detector smoothers, as well as the activation of the FLL in pull-in and steady-state stages.
• Added new Tracking parameter Tracking_XX.carrier_aiding, allowing enabling/disabling of carrier aiding to the code tracking loop.
• New PVT parameter PVT.enable_rx_clock_correction allows to enable or disable the continuous application of the Time solution correction (clock steering) to the computation of Observables. By default is set to false (that is, disabled).
• New PVT parameter PVT.max_clock_offset_ms: if PVT.enable_rx_clock_correction is set to false, this parameter sets the maximum allowed local clock offset with respect to the Time solution. If the estimated offset exceeds this parameter, a clock correction is applied to the computation of Observables.
• Fixed L5 and E5a receiver chains when tracking the data component.
• Added new PVT configuration parameter PVT.rinex_name to specify a custom name of the generated RINEX files. A commandline flag --RINEX_name is also available, and overrides the configuration.

Improvements in Interoperability:

• Fixed PVT solution in receivers processing L1 plus L2C and/or L5 signals.
• Fixed the initialization of the carrier phase accumulator. Carrier phase measurements are now usable to compute integer ambiguity resolution.
• Added carrier phase observable initialization to match the pseudorange length.
• Added RINEX files generation for triple-band configurations (L1 + L2C + L5 and L1 + E1 + L2C + L5 + E5a).
• Fixed bugs in the decoding of BeiDou navigation messages.
• Fixed bugs in the generation of RTCM messages.
• Fixed a bug in feeding Galileo channels' observations to RTKLIB, which was causing wrong date of PVT fixes in Galileo-only receivers and not considering Galileo observations in multi-constellation receivers when using signals after the GPS rollover on April 6, 2019.
• Improved management of devices with the AD9361 RF transceiver.
• Fixed bugs in FPGA off-loading.

Improvements in Maintainability:

• Rewriting of acquisition and tracking adapters, thus avoiding a lot of code duplication.
• New CMake option -DENABLE_ARMA_NO_DEBUG defines the macro ARMA_NO_DEBUG, which disables all run-time checks, such as bounds checking, in the Armadillo library. This will result in faster code. This option is disabled by default during development, but automatically set to ON if the option ENABLE_PACKAGING is set to ON.
• All shadowed variables detected by passing -Wshadow to the compiler have been fixed (see https://rules.sonarsource.com/cpp/RSPEC-1117?search=shadow and MISRA C++:2008, 2-10-2 - Identifiers declared in an inner scope shall not hide an identifier declared in an outer scope).
• Apply more clang-tidy checks related to readability: readability-avoid-const-params-in-decls, readability-braces-around-statements, readability-isolate-declaration, readability-redundant-control-flow, and readability-uppercase-literal-suffix. Fixed raised warnings.
• Fixed a number of defects detected by cpplint.py. Filters applied: +build/class, +build/c++14, +build/deprecated, +build/explicit_make_pair, +build/include_what_you_use, +build/printf_format, +build/storage_class, +readability/constructors, +readability/namespace, +readability/newline, +readability/utf8, +runtime/casting, +runtime/explicit, +runtime/indentation_namespace, +runtime/init, +runtime/invalid_increment, +runtime/member_string_references, +runtime/memset, +runtime/operator, +runtime/printf, +runtime/printf_format, and +whitespace/blank_line.
• clang-format can now be applied to the whole code tree without breaking compilation.
• Added more check options to .clang-tidy file.
• Default Python version is now >= 3.4. Python 2.7 still can be used in systems where Python 3 is not available (e.g., CentOS 7, Debian 8, Ubuntu 10.04).
• CMake now passes the -DCMAKE_BUILD_TYPE (or configuration in multi-configuration generators like Xcode) to modules built along with gnss-sdr (e.g, the volk_gnsssdr library and googletest). Build types available: None, Release (by default), Debug, RelWithDebInfo, MinSizeRel, Coverage, NoOptWithASM, O2WithASM, O3WithASM, ASAN.
• Fix runtime errors when compiling in Debug mode on macOS.
• Updated links in comments through the source code and in CMake scripts.
• Update GSL implementation to 0.36.0. See https://github.com/gsl-lite/gsl-lite/releases/tag/v0.36.0
• Create a CI job on GitHub to ensure that clang-tidy has been applied in most of the source code (some optional blocks and tests are left apart).
• Create a CI job on GitHub to ensure that clang-format has been applied.
• Create a CI job on GitHub to ensure that cpplint filters have been applied.
• Create a CI job on GitHub to ensure compliance with REUSE Specification (see https://reuse.software)
• Create a CI job on GitHub using prettier (https://prettier.io/) to check markdown files formatting.
• Create a CI job on GitHub to check the formatting of CMake scripts using cmakelint (see https://github.com/richq/cmake-lint).

Improvements in Openness:

• Make software compliant with REUSE Specification – Version 3.0 (see https://reuse.software/spec/).

Improvements in Portability:

• The CMake scripts now find dependencies in Debian's riscv64 architecture.
• Enable AVX2 kernels of the volk_gnsssdr library when using the Clang compiler.
• Fixed building in some ARM-based devices. Now Clang and ARMClang can be used for native building.
• Added toolchain files for building gnss-sdr and the volk_gnsssdr library in several ARM processor architectures, including those in Raspberry Pi 3 and 4.
• The software can now be built using Xcode (passing -GXcode to CMake) without previous manual installation of volk_gnsssdr.
• The software can now be built using Xcode (passing -GXcode to CMake) without gflags, glog, matio, PugiXML, Protocol Buffers or googletest previously installed.
• Now the volk_gnsssdr library can be built on Microsoft Windows.
• Now the volk_gnsssdr library makes use of C11 aligned_alloc where available.
• Improved CMake script for cross-compilation and for the detection of AVX, AVX2 and NEON (v7 and v8) instructions.
• Fixed warnings raised by CMake 3.17.
• Fixed warnings raised by cmake --warn-uninitialized ..
• Fixed the receiver's availability in systems in which the Sys V message queue mechanism is not available.

Improvements in Reliability:

• Decoding of navigation messages no longer rely on implementation defined behavior for shifting left a signed integer.
• Removed usage of functions with insecure API (e.g., strcpy, sprintf).
• New type alias volk_gnsssdr::vector allows both aligned memory allocation and automatic deallocation.
• Fixed a memory leak in the generation of Galileo PRN codes.
• Added clang-tidy checks clang-analyzer-security.*, clang-analyzer-optin.portability.UnixAPI clang-tidy checks. Fixed raised warnings.
• Fixed cpplint.py runtime/printf and runtime/explicit errors.
• All constructors callable with one argument are marked with the keyword explicit. See MISRA C++:2008, 12-1-3 - All constructors that are callable with a single argument of fundamental type shall be declared explicit.

Improvements in Repeatability:

• Added the option to apply carrier smoothing of code pseudoranges with new Observables parameter Observables.enable_carrier_smoothing.
• Fixed normalization of DLL discriminator in BPSK modulations when the spacing between correlators was not 0.5.

Improvements in Testability:

• Add receiver runtime to position_test report.
• Improvements in FPGA unit tests.
• Add new utility tool obsdiff to perform single and double differences computations from observation RINEX files. Requires GPSTk and Armadillo >= 9.800.

Improvements in Usability:

• A new global parameter GNSS-SDR.pre_2009_file allows to process raw sample files containing GPS L1 C/A signals dated before July 14, 2009.
• Improved DLL-PLL binary dump MATLAB/Octave plot script. Old versions removed.
• Simplified RTKLIB error log.
• Added a Python 3 plotting script to show relative performance of generic volk_gnsssdr kernels wrt. SIMD fastest versions.
• Added reporting of velocity in the terminal.
• Added reporting of user clock drift estimation, in ppm, in the Pvt_Monitor and in internal logging (Debug mode).
• Updated documentation generated by Doxygen, now the pdfmanual target works when using ninja.
• CMake now generates an improved summary of required/optional dependency packages found and enabled/disabled features, including the building system and GNSS-SDR, CMake and compiler versions. This info is also stored in a file called features.log in the building directory.
• Markdown files have been wrapped to 80 characters line length to make it easier to read them from the terminal.

See the definitions of concepts and metrics at https://gnss-sdr.org/design-forces/

 

GNSS-SDR v0.0.11 - 2019-08-04

This release has several improvements in different dimensions, addition of new features and bug fixes:

Improvements in Accuracy:

• Local clock correction based on PVT solution, allowing the delivery of continuous observables.
• Fix a bug in broadcast ionospheric parameters usage.

Improvements in Availability:

• Improved mechanism for false lock detection in the Tracking loops.
• Fixed bug in Galileo INAV/FNAV message decoding when PLL is locked at 180 degrees, which prevented from correct navigation message decoding in some situations.
• Fixed bug that caused a random deadlock in the Observables block, preventing the computation of PVT fixes.
• Fixed PVT computation continuity through the TOW rollover.
• Improved signal acquisition and tracking mechanisms in high dynamic scenarios.

Improvements in Efficiency:

• Added mechanism for assisted acquisition of signals on a secondary band when the primary has already been acquired. This allows a great reduction of the computational load in multi-frequency configurations.
• Tracking loops now perform bit synchronization, simplifying the decoding process in Telemetry blocks and FPGA-offloading.
• Improved preamble detection implementation in the decoding of navigation messages (acceleration by x1.6 on average per channel).
• Shortened Acquisition to Tracking transition time.
• Applied clang-tidy checks and fixes related to performance: performance-faster-string-find, performance-for-range-copy, performance-implicit-conversion-in-loop, performance-inefficient-algorithm, performance-inefficient-string-concatenation, performance-inefficient-vector-operation, performance-move-const-arg, performance-move-constructor-init, performance-noexcept-move-constructor, performance-type-promotion-in-math-fn, performance-unnecessary-copy-initialization, performance-unnecessary-value-param, readability-string-compare.

Improvements in Flexibility:

• Rewritten Control Thread and GNSS flow graph for increased control of channels' status and smarter assignation of satellites in multi-band configurations.
• New Tracking parameters allow the configuration of PLL and DLL filters order.
• Added parameter to enable FLL during pull-in time.
• Configurable pull-in time in the Tracking loops.

Improvements in Interoperability:

• Added the BeiDou B1I and B3I receiver chains.
• Fix bug in GLONASS dual frequency receiver.
• Added a custom UDP/IP output for PVT data streaming.
• Improved Monitor block with UDP/IP output for internal receiver's data streaming.
• Custom output formats described with .proto files, making easier to other applications reading them in a forward and backward-compatible fashion upon future format changes. New dependency: Protocol Buffers >= 3.0.0
• Fixes in RINEX generation: week rollover, annotations are not repeated anymore in navigation files. Parameter PVT.rinexnav_rate_ms has been removed, annotations are made as new ephemeris arrive.
• Fixes in RTCM messages generation: week rollover.

Improvements in Maintainability:

• The internal communication mechanism based on gr::msg_queue has been replaced by a thread-safe, built-in asynchronous message passing system based on GNU Radio's Polymorphic Types. This change is backwards-compatible and prevents from a failure in case of a possible future deprecation or removal of the gr::msg_queue API.
• Deprecated boost::asio::io_service replaced by boost::asio::io_context if Boost > 1.65
• CMake turns all policies to ON according to the running version up to version 3.15.
• Usage of clang-tidy integrated into CMake scripts. New option -DENABLE_CLANG_TIDY=ON executes clang-tidy along with compilation. Requires clang compiler.
• Applied clang-tidy checks and fixes related to readability: readability-container-size-empty, readability-identifier-naming, readability-inconsistent-declaration-parameter-name, readability-named-parameter, readability-non-const-parameter, readability-string-compare.
• Improved includes selection following suggestions by include-what-you-use (see https://include-what-you-use.org/), allowing faster compiles, fewer recompiles and making refactoring easier.
• Massive reduction of warnings triggered by clang-tidy checks.
• Throughout code cleaning and formatting performed with automated tools in order to reduce future commit noise.

Improvements in Portability:

• Added interfaces for FPGA off-loading in GPS L1 C/A, Galileo E1b/c, GPS L2C, GPS L5 and Galileo E5a receiver chains.
• CMake scripts now follow a modern approach (targets and properties) but still work with 2.8.12.
• Improvements for macOS users using Homebrew.
• The software builds against GNU Radio >= 3.7.3, including 3.8.0. Automatically detected, no user intervention is required.
• The volk_gnsssdr library can now be built without requiring Boost if the compiler supports C++17 or higher.
• The Boost Filesystem library is not anymore a required dependency in cases where it can be replaced by std::filesystem. Automatically detected, no user intervention is required.
• CMake scripts automatically select among C++11, C++14, C++17, or C++20 standards, the most recent as possible, depending on compiler and dependencies versions.
• Drawback in portability: Protocol Buffers >= 3.0.0 is a new required dependency.

Improvements in Reliability:

• Included the Guidelines Support Library. General improvement of memory management, replacement of raw pointers by containers or smart pointers.
• Applied clang-tidy checks and fixes related to High Integrity C++: performance-move-const-arg, modernize-use-auto, modernize-use-equals-default, modernize-use-equals-delete, modernize-use-noexcept, modernize-use-nullptr, cert-dcl21-cpp, misc-new-delete-overloads, cert-dcl58-cpp, cert-err52-cpp, cert-err60-cpp, hicpp-exception-baseclass, hicpp-explicit-conversions.
• Fixed a number of defects detected by Coverity Scan (version June 2019).

Improvements in Usability:

• The receiver now admits FPGA off-loading, allowing for real time operation in embedded systems at high sampling rates and high number of signals and channels per signal in multiple bands.
• Fixed program termination (avoiding hangs and segfaults in some platforms/configurations).
• The Labsat_Signal_Source now terminates the receiver's execution when the end of file(s) is reached. It now accepts LabSat 2 filenames and series of LabSat 3 files.
• Added configuration parameters to set the annotation rate in KML, GPX, GeoJSON and NMEA outputs, set by default to 1 s.
• New parameter PVT.show_local_time_zone displays time in the local time zone. Subject to the proper system configuration of the machine running the software receiver. This feature is not available in old compilers.
• CMake now generates a summary of required/optional dependency packages found and enabled/disabled features. This info is also stored in a file called features.log in the building directory.
• Improved information provided to the user in case of building configuration and runtime failures.
• Remove abandoned building option -DENABLE_GN3S and Gn3s_Signal_Source implementation.

See the definitions of concepts and metrics at https://gnss-sdr.org/design-forces/

 

GNSS-SDR v0.0.10 - 2018-12-14

This release has several improvements in different dimensions, addition of new features and bug fixes:

Improvements in Accuracy:

• Part of the RTKLIB core library has been integrated into GNSS-SDR. There is now a single PVT block implementation which makes use of RTKLIB to deliver PVT solutions, including Single and PPP navigation modes.
• Fixed CN0 estimation for other correlation times than 1 ms.
• Improved computation of tracking parameters and GNSS observables.
• Other minor bug fixes.

Improvements in Availability:

• Internal Finite State Machines rewritten for improved continuity in delivering position fixes. This fixes a bug that was stalling the receiver after about six hours of continuous operation.
• Redesign of the time counter for enhanced continuity.
• Improved flow graph in multi-system configurations: the receiver does not get stalled anymore if no signal is found from the first system.
• Improved acquisition and tracking sensitivity.
• Added mechanisms for Assisted GNSS, thus shortening the Time-To-First-Fix. Provision of data via XML files or via SUPL v1.0. Documented at https://gnss-sdr.org/docs/sp-blocks/global-parameters/
• Other minor bug fixes.

Improvements in Efficiency:

• Added the possibility of non-blocking acquisition, which works well when using real-time data from an RF front-end.
• Improved flow graph in multi-band configurations: satellites acquired in one band are immediately searched in others.
• Complex local codes have been replaced by real codes, alleviating the computational burden.
• New volk_gnsssdr kernels: volk_gnsssdr_16i_xn_resampler_16i_xn.h, volk_gnsssdr_16ic_16i_rotator_dot_prod_16ic_xn.h, volk_gnsssdr_32f_xn_resampler_32f_xn.h, and volk_gnsssdr_32fc_32f_rotator_dot_prod_32fc_xn.h.
• Some AVX2 implementations added to the volk_gnsssdr library.
• Improvement in C++ usage: Use of const container calls when result is immediately converted to a const iterator. Using these members removes an implicit conversion from iterator to const_iterator.
• Output printers can be shut down, with some savings in memory and storage requirements.
• A number of code optimizations here and there.

Improvements in Flexibility:

• A number of new parameters have been exposed to the configuration system.
• Possibility to choose Pilot or Data component for tracking of GPS L5 and Galileo E5a signals.
• Enabled extended coherent integration times for signal tracking.
• Configurable coherent and/or non-coherent signal acquisition.
• Some configuration parameters can now be overridden by commandline flags for easier use in scripts.

Improvements in Interoperability:

• Added the GPS L5 receiver chain.
• Added the GLONASS L1 SP receiver chain.
• Added the GLONASS L2 SP receiver chain.
• Improvements in the Galileo E5a and GPS L2C receiver chains.
• Updated list of available GNSS satellites.
• Added five more signal sources: Fmcomms2_Signal_Source (requires gr-iio), Plutosdr_Signal Source (requires gr-iio), Spir_GSS6450_File_Signal_Source, Labsat_Signal_Source and Custom_UDP_Signal_Source (requires libpcap). Documented in https://gnss-sdr.org/docs/sp-blocks/signal-source/
• Improved support for BladeRF, HackRF and RTL-SDR front-ends.
• Added tools for the interaction with front-ends based on the AD9361 chipset.
• Intermediate results are now saved in MAT-file format (.mat), readable from Matlab/Octave and from Python via h5py.
• Added the GPX output format.
• Improvements in the generation of KML files.
• Improvements in the NMEA output. The receiver can produce GPGGA, GPRMC, GPGSA, GPGSV, GAGSA and GAGSV sentences.
• Improvements in the RTCM server stability.
• Improvements in the correctness of generated RINEX files.
• The receiver can read and make use of Galileo almanac XML files published by the European GNSS Service Centre at https://www.gsc-europa.eu/gsc-products/almanac
• Own-defined XML schemas for navigation data published at https://github.com/gnss-sdr/gnss-sdr/tree/next/docs/xml-schemas
• Added program rinex2assist to convert RINEX navigation files into XML files usable for Assisted GNSS. Only available building from source. See https://github.com/gnss-sdr/gnss-sdr/tree/next/src/utils/rinex2assist

Improvements in Maintainability:

• Setup of a Continuous Integration system that checks building and runs QA code in a wide range of GNU/Linux distributions (Arch Linux, CentOS, Debian, Fedora, OpenSUSE, Ubuntu) and releases. See https://gitlab.com/gnss-sdr/gnss-sdr
• Creation of multi-system processing blocks, drastically reducing code duplication and maintainability time.
• Automated code formatting with clang-format. This tool is widely available and easy to integrate into many code editors, and it also can be used from the command line. It cuts time spent on adhering to the project's code formatting style.
• Improvement in C++ usage: C-style casts have been replaced by C++ casts. C-style casts are difficult to search for. C++ casts provide compile time checking ability and express programmers' intent better, so they are safer and clearer.
• Improvement in C++ usage: The override special identifier is now used when overriding a virtual function. This helps the compiler to check for type changes in the base class, making the detection of errors easier.
• Improvement in C++ usage: A number of unused includes have been removed. Order of includes set to: local (in-source) headers, then library headers, then system headers. This helps to detect missing includes.
• Improvement in C++ usage: Enhanced const correctness. Misuses of those variables are detected by the compiler.
• Improved code with clang-tidy and generation of a compile_commands.json file containing the exact compiler calls for all translation units of the project in machine-readable form if clang-tidy is detected.
• Applied some style rules to CMake scripts.
• Minimal versions of dependencies identified and detected.

Improvements in Portability:

• Several CMake scripts improvements, more verbose outputs in case of errors. Building configuration has been documented in https://gnss-sdr.org/docs/tutorials/configuration-options-building-time/
• Improved SDK for cross-compilation in embedded devices. Documented in https://gnss-sdr.org/docs/tutorials/cross-compiling/
• Improved control over minimum required versions for core dependencies.
• The software builds with C++11, C++14 and C++17 standards.
• The software can now be built using GCC >= 4.7.2 or LLVM/Clang >= 3.4.0 compilers on GNU/Linux, and with Clang/AppleClang on macOS.
• The Ninja build system can be used in replacement of make.
• The volk_gnsssdr library can be built using Python 2.7+ or Python 3.6+.
• The volk_gnsssdr library is now ready for AArch64 NEON instructions.
• Improved detection of required and optional dependencies in many GNU/Linux distributions and processor architectures.
• Improvement in C++ usage: The <ctime> library has been replaced by the more modern and portable <chrono> (except for the interaction with RTKLIB).
• Improvement in C++ usage: The <stdio.h> library has been replaced by the more modern and portable <fstream> for file handling.
• Improvement in C++ usage: C++ libraries preferred over C libraries (e.g., <cctype> instead of <ctype.h>, <cmath> instead of <math.h>).
• Fix compatibility with Boost 1.67 (closes Debian bug #911882 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=911882)
• Fixes required by Debian packaging.
• Fixes required by Macports packaging.
• A downside in portability: BLAS and LAPACK libraries are now required even in ARM devices.
• A downside in portability: the matio library >= 1.5.3 is a new required dependency. If not found, it is downloaded and built automatically at building time, but this requires libtool, automake and hdf5 already installed in the system.
• A downside in portability: the PugiXML library is a new required dependency. If not found, it is downloaded and built automatically at building time.

Improvements in Reliability:

• Introduced 3 new Input Filter implementations for pulsed and narrowband interference mitigation: Pulse_Blanking_Filter, Notch_Filter and Notch_Filter_Lite. Documented in https://gnss-sdr.org/docs/sp-blocks/input-filter/
• Improved flow graph stability.
• Introduction of high-integrity C++ practices into the source code and included in the coding style guide. See https://gnss-sdr.org/coding-style/
• Fixed a number of defects detected by Coverity Scan.
• Improvement of QA code and addition of a number of new tests. Documented at https://gnss-sdr.org/docs/tutorials/testing-software-receiver-2/
• Improvement in C++ usage: rand() function replaced by <random> library.
• Improvement in C++ usage: strlen and strncpy have been replaced by safer C++ counterparts.
• Improvement in C++ usage: Some destructors have been fixed, avoiding segmentation faults when exiting the program.
• Website switched from http to https. Links in the source tree switched when available.

Improvements in Reproducibility:

• Setup of a Continuous Reproducibility system at GitLab for the automatic reproduction of experiments. The concept was introduced in https://ieeexplore.ieee.org/document/8331069/ Example added in the src/utils/reproducibility/ieee-access18/ folder.
• Fixes of Lintian warnings related to build reproducibility.

Improvements in Scalability:

• Improvements in multi-system, multi-band receiver configurations. The receiver now accepts any number of channels and systems in the three available bands.
• All possible combinations of signals and integration times are now accepted by the Observables block.

Improvements in Testability:

• Several Unit Tests added. Documentation of testing concepts and available tests at https://gnss-sdr.org/docs/tutorials/testing-software-receiver/
• New extra unit test AcquisitionPerformanceTest checks the performance of Acquisition blocks.
• New extra unit test TrackingPullInTest checks acquisition to tracking transition.
• New extra unit test HybridObservablesTest checks the generation of observables.
• Improved system testing: position_test accepts a wide list of parameters and can be used with external files.
• Receiver channels can now be fixed to a given satellite.
• Testing integrated in a Continuous Reproducibility system (see above).
• Improved CTest support in volk_gnsssdr.

Improvements in Usability:

• All Observables block implementations have been merged into a single implementation for all kinds of GNSS signals, making it easier to configure.
• All PVT block implementations have been merged into a single implementation for all kinds of GNSS signals, making it easier to configure.
• Misleading parameter name GNSS-SDR.internal_fs_hz has been replaced by GNSS-SDR.internal_fs_sps. The old parameter name is still read. If found, a warning is provided to the user. The old name will be removed in future releases.
• Updated and improved online documentation of processing blocks at https://gnss-sdr.org/docs/sp-blocks/
• Improved documentation of required dependency packages in several GNU/Linux distributions.
• Dump and output files can now be stored anywhere.
• Parameter names with the same role have been harmonized within different block implementations.
• Added a changelog, a code of conduct, a contributing guide and a pull-request template in the source tree.
• Added colors to the commandline user interface.
• Updated manfiles.
• Updated examples of configuration files under the conf/ folder.

See the definitions of concepts and metrics at https://gnss-sdr.org/design-forces/

 

GNSS-SDR v0.0.9 - 2017-02-13

This release has several improvements, addition of new features and bug fixes in many dimensions:

Improvements in Accuracy:

• Major rewriting in the generation of pseudoranges.
• Fixed bug in Galileo E5a/I codes.
• Fixed bug in Galileo E1 correlator spacing.
• Fixed bug that was causing errors in receivers above the troposphere.
• Fixed 16-bit complex resampler.
• Improved time tracking algorithm.
• Added Bancroft's algorithm implementation for PVT initialization.

Improvements in Availability:

• Improved numerical stability of the PVT solution. The infamous bug that was causing apparently random error peaks has finally been fixed.

Improvements in Efficiency:

• VOLK_GNSSSDR: Added NEON,AVX and unaligned protokernels for volk_gnsssdr_32f_index_max_32 kernel.
• VOLK_GNSSSDR: Added volk_gnsssdr-config-info to the list of generated executables.

Improvements in Flexibility:

• Added maximum number of dwells in the Tong algorithm.

Improvements in Interoperability:

• Added six new Galileo satellites: FM7, FM10, FM11, FM12, FM13, FM14.
• The Hybrid_Observables and Hybrid_PVT implementations can now handle more types of GNSS signals.
• The RINEX printer can now print L2C and E5a observables and navigation files, including multiband configurations.
• Added RTCM 3.2 output to more receiver configurations.

Improvements in Maintainability:

• The VOLK_GNSSSDR library can now be built with Python 3. Switched dependencies for VOLK_GNSSDR: from (old, python2.7-only) python-cheetah templates to Python3 friendly python-mako and python-six. So, Python-cheetah dependency has been dropped, and python-mako and python-six have been added.
• If suitable versions of gflags, glog, armadillo or googletest are not found in the system, they will be downloaded and built at compile time (versions 2.2.0, 0.3.4, 7.600.2 and 1.8.0, respectively).
• Fixed more than 30 defects detected by Coverity Scan.
• Added CMake Python finder and module checker.
• Deleted files related to CPack.
• Fixes, updates and improvements in the documentation.
• Improvements in CMake scripts: General code cleaning and addition of comments. Improved user information in case of failure. Improved detection of dependencies in more processor architectures (e.g. aarch64).

Improvements in Marketability:

• Reduced time from a commit to deployment (see virtualization mechanisms in Portability).

Improvements in Portability:

• Now GNSS-SDR can be run in virtual environments through snap packages (see https://github.com/carlesfernandez/snapcraft-sandbox) and docker images (see https://github.com/carlesfernandez/docker-gnsssdr).
• Now GNSS-SDR is adapted to cross-compiling environments for embedded devices (see https://github.com/carlesfernandez/oe-gnss-sdr-manifest).
• BLAS and LAPACK libraries are no longer mandatory on ARM devices.

Improvements in Scalability:

• Fixed bug in acquisition with rata rates higher than 16 Msps in 4ms code periods.

Improvements in Testability:

• Major QA source code refactoring: they has been split into src/tests/unit-tests and src/tests/system-tests folders. They are optionally built with the ENABLE_UNIT_TESTING=ON (unit testing QA code), ENABLE_UNIT_TESTING_EXTRA=ON (unit tests that require extra files downloaded at configure time), ENABLE_SYSTEM_TESTING=ON (system tests, such as measurement of Time-To-First-Fix) and ENABLE_SYSTEM_TESTING_EXTRA=ON (extra system test requiring external tools, automatically downloaded and built at building time) configuration flags. The EXTRA options also download and build a custom software-defined signal generator and version 2.9 of GPSTk, if not already found on the system. Download and local link of version 2.9 can be forced by ENABLE_OWN_GPSTK=ON building configuration flag. Only ENABLE_UNIT_TESTING is set to ON by default.
• Unit tests added: CPU_multicorrelator_test and GPU_multicorrelator_test measure computer performance in multicorrelator setups.
• Unit tests added: GpsL1CADllPllTracking and GpsL1CATelemetryDecoderTest.
• System test added: ttff_gps_l1 performs a set of cold / assisted runs of the software receiver and computes statistics about the obtained Time To First Fix.
• System test added: obs_gps_l1_system_test uses an external software-defined signal generator to produce raw digital GNSS signal from a RINEX navigation file and a position (static or dynamic), processes it with GNSS-SDR, and then compares the RINEX observation file produced by the software receiver to that produced by the signal generator.
• Software Development Kit provided for embedded devices (see https://gnss-sdr.org/docs/tutorials/cross-compiling/).

Improvements in Usability:

• Now the block factory automatically detects Channel input data type, so it is no longer required to specify Channel.input_type in the configuration. An error raises if Acquisition and Tracking Blocks are not configured with the same input data type.
• Block names changed from L2_M to L2C.
• Documentation available at https://gnss-sdr.org/docs/
• Improved tools for compilation, execution and testing in embedded devices.

See the definitions of concepts and metrics at https://gnss-sdr.org/design-forces/

 

GNSS-SDR v0.0.8 - 2016-07-04

This is a maintenance and bug fix release with no relevant new features with respect to v0.0.7. The main changes are:

• Fixed a bug that broke building when using latest VOLK release
• Updated PYBOMBS instructions
• Added Tests for FFT length
• Added Tests for CUDA-based tracking
• Added Tests for SIMD-based tracking
• Improved CUDA-based correlation.
• Updated documentation
• Fixed building in mips and powerpc architectures.
• gr-gn3s and gr-dbfcttc moved to its own repository.
• Improved package reproducibility
• VOLK_GNSSSDR: Fixed a bug in AVX2 puppet
• VOLK_GNSSSDR: can now be built using the C98 standard
• VOLK_GNSSSDR: Fixed a bug that broke building when linking to Boost in some configurations.
• VOLK_GNSSSDR: Added an option to trigger profiling at building time.
• VOLK_GNSSSDR: Fix the CMake-based check for posix_memalign.

 

GNSS-SDR v0.0.7 - 2016-05-15

This release has several improvements, addition of new features and bug fixes:

• Improvements in receiver design: Internal block communication has been redesigned to accommodate the addition of new signals, and now upstream and downstream communication within blocks is implemented through the GNU Radio block’s asynchronous message passing system, leading to a more scalable, more robust and cleaner design.
• Improvements in receiver design: Correlators have been rewritten to take full advantage of VOLK and VOLK_GNSSSDR, and they are of general use for any tracking block. Their API now admit an arbitrary number of correlators, spaced in an arbitrary manner, in 16ic and 32fc versions.
• Improvements in receiver design: Block adapters are now all managed by smart pointers, ensuring better memory management.
• Improvements in processing speed: The VOLK_GNSSSDR library has been rewritten, following current VOLK standards and adding a number of new kernels. This approach addresses both efficiency and portability. Now the library provides the key kernels for GNSS signal processing in 16ic and 32fc versions, including SSE2, SSE3, SSE4.1, AVX, AV2 and NEON implementations. Please execute volk_gnsssdr_profile and volk_profile to use the fastest implementation for your host machine.
• New source block: Two_Bit_Packed_File_Signal_Source. This block takes 2 bit samples that have been packed into bytes or shorts as input and generates a byte for each sample.
• Fixes in SUPL assistance (supl.nokia.com removed).
• Improvements in acquisition: Added a non CFAR PCPS acquisition algorithm based on the estimation of the post correlation noise floor. If enabled as an option in the acquisition configuration, it allows setting more stable thresholds in the presence of non-gaussian front-end noise (which is the usual behavior of front-ends.)
• Fixes in acquisition: Fixed mismatch between the config files and the acquisition code in the specification of the IF. Fixed a bug in the length of the FFT of local codes.
• Improvements in tracking sensitivity: Added configuration option to customize the extension of the GPS L1 CA correlation length after bit synchronization (options are: [1,2,4,5,10,20] ms). Only available in the GPS_L1_CA_DLL_PLL_C_Aid_Tracking implementation.
• New tracking block introduced: GPS_L1_CA_DLL_PLL_C_Aid_Tracking is a GPS L1 C/A carrier PLL and code DLL with optional carrier-aid feedback. It is available in both 32 bits gr_complex input samples and in 16 bits short int complex samples. The gr_complex version has also the capability to extend the coherent correlation period from 1 ms to 20 ms using telemetry symbol synchronization.
• Increased resolution in CN0 estimator internal variables.
• Fixed a bug in computation of GPS L1 C/A carrier phase observable.
• Fixed a bug in the internal state machine that was blocking the receiver after a few hours of usage. Now the receiver can work continually (tested for more than one week, no known limit).
• New tracking block introduced: GPS_L1_CA_DLL_PLL_Tracking_GPU is a GPS L1 C/A carrier PLL and code DLL that uses the CUDA-compatible GPU to compute carrier wipe off and correlation operations, alleviating the CPU load.
• Obsolete/buggy blocks removed: GPS_L1_CA_DLL_FLL_PLL_Tracking, GPS_L1_CA_DLL_PLL_Optim_Tracking.
• Added a RTCM printer and TCP server in PVT blocks (still experimental). The receiver is now able to stream data in real time, serving RTCM 3.2 messages to multiple clients. For instance, it can act as a Ntrip Source feeding a Ntrip Server, or to be used as data input in RTKLIB, obtaining Precise Point Positioning fixes in real-time. The TCP port, Station ID, and rate of MT1019/MT1045 and MSM can be configured. GPS_L1_CA_PVT serves MT1019 (GPS Ephemeris) and MSM7 (MT1077, full GPS pseudoranges, phase ranges, phase range rates and CNR - high resolution) messages, while GALILEO_E1_PVT serves MT1045 (Galileo ephemeris) and MSM7 (MT1097, full Galileo pseudoranges, phase ranges, phase range rates and CNR - high resolution).
• Added a GeoJSON printer. Basic (least-squares) position fixes can be now also stored in this format, in addition to KML.
• Obsolete block removed: output filter.
• QA code migrated to the new asynchronous message passing system.
• Improvements in documentation: update of README.md file, addition of documentation for the VOLK_GNSSSDR library, updated links to new ICDs.
• Improvements in documentation: Satellite identification updated to current constellation status.
• Updated and cleaner console output. Now Galileo satellites have the ‘E’ identifier in their PRN number.
• Several improvements in CMake scripts allow to build GNSS-SDR in Linux Debian (Jessie, Stretch and Sid), Ubuntu (from 12.04 to 16.04), including amd64, i386, armhf and arm64 architectures, and possibly in other GNU/Linux distributions, as well as in Mac OS X 10.9 to 10.11. It also works well with CMake 3.5 (some problems solved with VOLK_GNSSSDR as a sub-project).
• The software can link either against OpenSSL or against GnuTLS with openssl extensions, whatever it is available. This allows buildings in distributions such as Fedora or ArchLinux, while being compatible with binary distribution through Debian packages.
• Fixed a number of defects detected by Coverity Scan.
• Some fixes required by Debian licensing and packaging system.
• Added a CGRAN (https://www.cgran.org/) manifest
• Lots of code cleaning and fixes of typos and small bugs.

 

GNSS-SDR v0.0.6 - 2015-09-02

This release has several improvements and bug fixes:

• Added initial support to multi-band, multi-source configurations (multiple signal sources and signal conditioners).
• Updated configuration files to new notation. Old and new configuration notations still compatible.
• Added skeleton for mixed (multi-frequency and multi-system) observables block.
• Faster local carrier update (25% of improvement).
• Added initial support to GPS L2C real time tracking and decoding of CNAV message with NSL STEREO v2, Fraunhofer’s Flexiband, and USRPx front-ends (the latter requiring external clock).
• Added initial support to select the frontend clock reference source in UHD signal source (i.e. internal or external clock reference).
• Added 2 bits complex file source for GNSS-SDR GSoC 2015 signal sampler designed by Ajith Peter.
• Added a new rtl_tcp signal source, remote access to RTL2832U-based dongles via TCP.
• Always build front-end-cal, a calibration tool for some DVB-T receivers based on the Realtek's RTL2832U chipset.
• Fixed bug in UTC time computation for GPS signals.
• Updated satellite identification for GPS and Galileo.
• Defined cbyte as a new input data type (std::complex<signed char>).
• Adding a new data_type_adapter, from interleaved short to std::complex<short>.
• Adding a filter for complex short streams.
• Adding a fir_filter for std::complex<signed char> (aka cbyte). It converts the data type to floats, filters, and converts back to cbyte.
• Added a resampler for cbytes and cshorts.
• First working version of a GPS tracking block implementation using CUDA with multi-GPU device support.
• Updating RINEX obs header when leap second is available.
• Updating RINEX nav file when IONO and UTC data are available.
• Include Signal Strength Indicator in RINEX observable files.
• Tests fixed.
• Fixed more than 200 code defects detected by Coverity Scan.
• Updated documentation.
• Updated documentation and CMake scripts for the GN3S v2 driver (Linux-only)
• Armadillo version automatically downloaded and built if it is not present in the system is now 5.400.3.
• Updated old links from googlecode to new links at GitHub for Google Test, gflags, glog and gperftools.
• gfortran is no longer a required package, but it is used if available.
• Added an option to remove logging.
• Enabled cross-compilation for ARM devices.
• Lots of code cleaning.

 

GNSS-SDR v0.0.5 - 2015-01-13

This release has several improvements and bug fixes:

• Now GNSS-SDR can be installed on the system with the usual cmake ../ && make && sudo make install.
• Added volk_gnsssdr library, a volk-like library implementing some specific kernels and ensuring portable executables. It comes with a volk_gnsssdr_profile executable, in the fashion of volk_profile. Volk and volk_gnsssdr are compatible and can be mixed together. This is expected to enable faster execution of the software receiver in upcoming versions.
• The former rtlsdr_signal_source has been replaced by a more general osmosdr_signal_source compatible with all those front-ends accessible by the OsmoSDR driver (bladeRF, hackRF, etc.) in addition to RTL-based dongles.
• Added manpages when binaries gnss-sdr, volk_gnsssdr_profile and front-end-cal are installed.
• Now GNSS-SDR can be built on i386, amd64, armhf, armel and arm64 architectures.
• Now GNSS-SDR builds on Ubuntu 14.04 and 14.10, Debian jessie/sid and Mac OS X 10.9 and 10.10.
• Improved detection of dependencies, specially when installed as .deb packages.
• Added a check target with some minimal tests.
• Added support for interleaved I/Q byte-size sample files.
• Minor bug fixes, updated documentation and code cleaning.

 

GNSS-SDR v0.0.4 - 2014-09-08

This release has several improvements and bug fixes:

• Added hybrid processing GPS L1 C/A and Galileo E1B, providing position fixes make use of observables for both constellations.
• Added implementations of the QuickSync algorithm for GPS L1 C/A and Galileo E1 acquisition.
• Added processing blocks for Galileo E5a: Acquisition, Tracking, Telemetry_Decoder (experimental)
• New configuration files allow to configure GPS and Galileo channels in the same receiver.
• Added tropospheric corrections to GPS and Galileo PVT solution.
• Improved precision obtained by changing some variables from float to double.
• New building options: ENABLE_GN3S, ENABLE_RTLSDR, ENABLE_ARRAY, and ENABLE_OPENCL.
• Improved documentation on how to enable optional drivers.
• Fixed bug in memory alignment that caused problems with high data rates.
• Added ENABLE_GENERIC_ARCH, an option to build the binary without detecting the SIMD instruction set present in the compiling machine, so it can be executed in other machines without those specific sets.
• Added ENABLE_GPERFTOOLS, which links the executable to tcmalloc and profiler if Gperftools is available on the system.
• Added carrier phase, Doppler shift and signal strength observables to the RINEX files. Static PPP solutions are available for GPS with RTKLIB via RINEX files.
• The executable now produces RINEX files version 3.02 of Galileo Observables, Navigation data, and mixed (GPS/Galileo) observables and nav data. RINEX 3.02 is the default version of RINEX files.
• Armadillo version updated to 4.400.2
• Armadillo now uses OpenBLAS instead of BLAS if the former is available on the system.
• Some raw pointers have been changed to smart pointers.
• Minor bug fixes and code cleaning.

 

GNSS-SDR v0.0.3 - 2014-06-30

This release has several improvements and bug fixes, completing the transition from Subversion to Git. The main changes are:

• Created some missing directories lost in the SVN to Git transition.
• New C++11-ized block factory, flow graph and tests, resulting in better memory management and fewer segmentation faults. Several raw pointers converted to smart pointers.
• Reorganization of assistance data input and output.
• Fixed memory leak when talking to SUPL servers.
• Improved retrieval of assistance data.
• Fixing an error in a constant value related to Galileo.
• Inform users if the temporal folder is not /tmp.
• Fixes and additions to the documentation.
• README in markdown language so it looks better in Git repositories.
• Fixed a bug that prevented the update of all shared map structures (ephemeris, iono parameters, etc…).
• The configuration script now throws error if GCC is older than 4.7 or Boost is older than 1.45
• Improved detection / downloading & building if missing of Gflags and Glog.
• Improved detection / downloading & building if missing of Armadillo and related dependencies.
• Fixes many warnings that appeared when using CMake 3.0.
• Improved detection of GTEST_DIR variable.
• Include header files in libraries so IDEs such as Xcode can display them.

Enjoy it!