gnss-sdr/src/utils/rinex-tools/README.md

obsdiff

This program computes single-differences and double-differences from RINEX observation files.

Building

Requirements:

• Armadillo: A C++ library for linear algebra and scientific computing. This program requires version 9.800 or higher. If your installed Armadillo version is older, see below.
• Gflags: A C++ library that implements command-line flags processing. If not found in your system, the latest version will be downloaded, built and linked for you at building time.
• GNSSTK: The GNSSTk C++ Library, used for RINEX files reading. If not found in your system, the latest version will be downloaded, built and linked for you at building time.
• Matio: A MATLAB MAT File I/O Library, version >= 1.5.3. If it is not found, or an older version is found, CMake will download, build and link a recent version for you at building time.

Optional:

• Gnuplot: a portable command-line driven graphing utility.

This program is built along with GNSS-SDR if the options ENABLE_UNIT_TESTING_EXTRA or ENABLE_SYSTEM_TESTING_EXTRA are set to ON when calling CMake:

$ cmake -DENABLE_SYSTEM_TESTING_EXTRA=ON ..
$ make obsdiff
$ sudo make install

The last step is optional. Without it, you still will get the executable at ../install/obsdiff.

This program requires Armadillo 9.800 or higher. If the available Armadillo version is older, this program will not be built. If your local Armadillo installed version is older than 9.800, you can force CMake to download, build and link a recent one:

$ cmake -DENABLE_SYSTEM_TESTING_EXTRA=ON -DENABLE_OWN_ARMADILLO=ON ..
$ make obsdiff
$ sudo make install

This later option requires BLAS, LAPACK and GFortran already installed in your system.

Usage

Double differences (Pseudorange, Carrier Phase and Carrier Doppler) within Base and Rover receivers:

$ obsdiff --base_rinex_obs=base.20o --rover_rinex_obs=rover.20o

Double differences with receiver clock correction (Pseudorange, Carrier Phase and Carrier Doppler) within Base and Rover receivers:

$ obsdiff --base_rinex_obs=base.20o --rover_rinex_obs=rover.20o --rinex_nav=base.nav --remove_rx_clock_error=true

Single difference (Pseudorange, Carrier Phase and Carrier Doppler) with Base receiver only and a special duplicated satellites simulated scenario:

$ obsdiff --rover_rinex_obs=rover.20o --single_diff=true --dupli_sat=true --dupli_sat_prns=1,2,3,4

Where the list of duplicated satellites PRN pairs must be specified by --dupli_sat_prns flag (i.e., 1,2,3,4 indicates that the PRNs 1,2 share the same orbit. The same applies for PRNs 3,4)

Single difference of Pseudorange Rate vs. Carrier Phase rate for each satellite:

$ obsdiff --rover_rinex_obs=rover.20o --single_diff=true

There is some flexibility in how command-line flags may be specified. The following examples are equivalent:

$ obsdiff -base_rinex_obs=reference.20o
$ obsdiff --base_rinex_obs=reference.20o
$ obsdiff -base_rinex_obs reference.20o
$ obsdiff --base_rinex_obs reference.20o

For boolean flags, the possibilities are slightly different:

$ obsdiff --single_diffs
$ obsdiff --nosingle_diffs
$ obsdiff --single_diffs=true
$ obsdiff --single_diffs=false

(as well as the single-dash variant on all of these).

Despite this flexibility, we recommend using only a single form: --variable=value for non-boolean flags, and --variable/--novariable for boolean flags.

Available command-line flags:

Command-line flag	Default value	Description
--skip_obs_transitory_s	30.0	Skip the initial observable outputs to avoid transitory results [s].
--skip_obs_ends_s	5.0	Skip the lasts observable outputs to avoid transitory results [s].
--single_diffs	false	[true, false]: If true, the program also computes the single difference errors for Carrier Phase and Doppler measurements (requires LO synchronization between receivers).
--compare_with_5X	false	[true, false]: If true, the program compares the E5a Doppler and Carrier Phases with the E5 full Bw in RINEX (expect discrepancy due to the center frequencies difference).
--dupli_sat	false	[true, false]: If true, this flag enables special observable test mode where the scenario contains duplicated satellite orbits.
--dupli_sat_prns	1,2,3,4	List of duplicated satellites PRN pairs (i.e., 1,2,3,4 indicates that the PRNs 1,2 share the same orbit. The same applies for PRNs 3,4).
--base_rinex_obs	base.obs	Filename of reference RINEX observation file.
--rover_rinex_obs	rover.obs	Filename of tested RINEX observation file.
--remove_rx_clock_error	false	Compute and remove the receivers clock error prior to compute observable differences (requires a valid RINEX nav file for both receivers)
--rinex_nav	base.nav	Filename of reference RINEX navigation file. Only needed if remove_rx_clock_error is set to true.
--system	G	GNSS satellite system: G for GPS, E for Galileo.
--signal	1C	GNSS signal: 1C for GPS L1 CA, 1B for Galileo E1.
--show_plots	true	[true, false]: If true, and if gnuplot is found on the system, displays results plots on screen. Please set it to false for non-interactive testing.