diff --git a/.clang-format b/.clang-format
index c8cd017d2..57c1b1d78 100644
--- a/.clang-format
+++ b/.clang-format
@@ -53,7 +53,7 @@ IncludeBlocks: Merge
 IncludeCategories:
   - Regex:           '^.*.h"'
     Priority:        1
-  - Regex:           '^.*(benchmark|boost|gflags|glog|gnsssdr|gnuradio|gpstk|gsl|gtest|pmt|uhd|volk)/'
+  - Regex:           '^.*(benchmark|boost|gflags|glog|gnsssdr|gnuradio|gnsstk|gsl|gtest|pmt|uhd|volk)/'
     Priority:        2
   - Regex:           '^.*(armadillo|iio|matio|pugixml)'
     Priority:        2
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7379fa1e2..106465e95 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -113,6 +113,14 @@ endif()
 
 option(ENABLE_OWN_GNSSTK "Force to download, build and link gnsstk for system tests, even if it is already installed" OFF)
 
+if(NOT ENABLE_OWN_GNSSTK)
+    option(ENABLE_OWN_GPSTK "Force to download, build and link gnsstk for system tests, even if it is already installed" OFF)
+    if(ENABLE_OWN_GPSTK)
+        message(STATUS "WARNING: Option ENABLE_OWN_GPSTK is deprecated, please use ENABLE_OWN_GNSSTK")
+        set(ENABLE_OWN_GNSSTK ON)
+    endif()
+endif()
+
 option(ENABLE_INSTALL_TESTS "Install QA code system-wide" OFF)
 if(ENABLE_FPGA)
     set(ENABLE_INSTALL_TESTS ON)
@@ -663,7 +671,7 @@ endif()
 if(NOT (GNURADIO_VERSION VERSION_LESS 3.8) AND (LOG4CPP_READY_FOR_CXX17 OR GNURADIO_USES_SPDLOG))
     # Check if we have std::filesystem
     if(NOT (CMAKE_VERSION VERSION_LESS 3.8))
-        #if(NOT GPSTK_FOUND OR NOT (GPSTK_FOUND AND GPSTK_OLDER_THAN_8))  # Fix for GPSTk < 8.0.0
+        if(NOT GNSSTK_FOUND OR NOT (GNSSTK_FOUND AND GNSSTK_OLDER_THAN_8))  # Fix for GNSSTk < 8.0.0
             find_package(FILESYSTEM COMPONENTS Final Experimental)
             set_package_properties(FILESYSTEM PROPERTIES
                 URL "https://en.cppreference.com/w/cpp/filesystem"
@@ -671,7 +679,7 @@ if(NOT (GNURADIO_VERSION VERSION_LESS 3.8) AND (LOG4CPP_READY_FOR_CXX17 OR GNURA
                 PURPOSE "Work with paths, regular files, and directories."
                 TYPE OPTIONAL
             )
-        #endif()
+        endif()
         if(FILESYSTEM_FOUND)
             set(CMAKE_CXX_STANDARD 17)
             # if(CMAKE_VERSION VERSION_GREATER 3.13)
diff --git a/cmake/Modules/FindGNSSTK.cmake b/cmake/Modules/FindGNSSTK.cmake
index 48c4bcdc3..ba0accb6e 100644
--- a/cmake/Modules/FindGNSSTK.cmake
+++ b/cmake/Modules/FindGNSSTK.cmake
@@ -31,14 +31,27 @@ if(DEFINED ENV{GNSSTK_ROOT})
     )
 endif()
 
+unset(GNSSTK_INCLUDE_DIR CACHE)
+set(GNSSTK_USES_GPSTK_NAMESPACE FALSE)
 find_path(GNSSTK_INCLUDE_DIR gnsstk/Rinex3ObsBase.hpp
     PATHS ${GNSSTK_ROOT_USER_DEFINED}/include
           /usr/include
           /usr/local/include
           /opt/local/include
 )
-
-set(GNSSTK_NAMES gnsstk libgnsstk)
+set(GNSSTK_NAMES ${CMAKE_FIND_LIBRARY_PREFIXES}gnsstk${CMAKE_SHARED_LIBRARY_SUFFIX})
+if(NOT GNSSTK_INCLUDE_DIR)
+    find_path(GNSSTK_INCLUDE_DIR gpstk/Rinex3ObsBase.hpp
+        PATHS ${GNSSTK_ROOT_USER_DEFINED}/include
+              /usr/include
+              /usr/local/include
+              /opt/local/include
+    )
+    if(GNSSTK_INCLUDE_DIR)
+        set(GNSSTK_NAMES gpstk ${CMAKE_FIND_LIBRARY_PREFIXES}gpstk${CMAKE_SHARED_LIBRARY_SUFFIX})
+        set(GNSSTK_USES_GPSTK_NAMESPACE TRUE)
+    endif()
+endif()
 
 include(GNUInstallDirs)
 
@@ -61,6 +74,10 @@ if(GNSSTK_FOUND)
     unset(PACKAGE_VERSION)
     if(EXISTS ${CMAKE_INSTALL_FULL_DATADIR}/cmake/GNSSTK/GNSSTKConfigVersion.cmake)
         include(${CMAKE_INSTALL_FULL_DATADIR}/cmake/GNSSTK/GNSSTKConfigVersion.cmake)
+    else()
+        if(EXISTS ${CMAKE_INSTALL_FULL_DATADIR}/cmake/GPSTK/GPSTKConfigVersion.cmake)
+            include(${CMAKE_INSTALL_FULL_DATADIR}/cmake/GPSTK/GPSTKConfigVersion.cmake)
+        endif()
     endif()
     if(PACKAGE_VERSION)
         set(GNSSTK_VERSION ${PACKAGE_VERSION})
@@ -70,30 +87,40 @@ endif()
 
 if(GNSSTK_FOUND AND GNSSTK_VERSION)
     set_package_properties(GNSSTK PROPERTIES
-        DESCRIPTION "Library and suite of applications for satellite navigation (found: v${GNSSTK_VERSION})"
+        DESCRIPTION "The GNSSTk C++ Library (found: v${GNSSTK_VERSION})"
     )
 else()
     set_package_properties(GNSSTK PROPERTIES
-        DESCRIPTION "Library and suite of applications for satellite navigation"
+        DESCRIPTION "The GNSSTk C++ Library"
     )
 endif()
 
-#if(GNSSTK_FOUND AND NOT EXISTS ${GNSSTK_INCLUDE_DIR}/gnsstk/SatelliteSystem.hpp)
-#    set(GNSSTK_OLDER_THAN_8 TRUE)
-#endif()
+if(GNSSTK_FOUND AND GNSSTK_USES_GPSTK_NAMESPACE AND NOT EXISTS ${GNSSTK_INCLUDE_DIR}/gpstk/SatelliteSystem.hpp)
+    set(GNSSTK_OLDER_THAN_8 TRUE)
+endif()
 
 set_package_properties(GNSSTK PROPERTIES
     URL "https://github.com/SGL-UT/gnsstk/"
+    TYPE OPTIONAL
 )
 
 if(GNSSTK_FOUND AND NOT ENABLE_OWN_GNSSTK AND NOT TARGET Gnsstk::gnsstk)
     add_library(Gnsstk::gnsstk SHARED IMPORTED)
-    set_target_properties(Gnsstk::gnsstk PROPERTIES
-        IMPORTED_LINK_INTERFACE_LANGUAGES "CXX"
-        IMPORTED_LOCATION "${GNSSTK_LIBRARY}"
-        INTERFACE_INCLUDE_DIRECTORIES "${GNSSTK_INCLUDE_DIR};${GNSSTK_INCLUDE_DIR}/gnsstk"
-        INTERFACE_LINK_LIBRARIES "${GNSSTK_LIBRARY}"
-    )
+    if(GNSSTK_USES_GPSTK_NAMESPACE)
+        set_target_properties(Gnsstk::gnsstk PROPERTIES
+            IMPORTED_LINK_INTERFACE_LANGUAGES "CXX"
+            IMPORTED_LOCATION "${GNSSTK_LIBRARY}"
+            INTERFACE_INCLUDE_DIRECTORIES "${GNSSTK_INCLUDE_DIR};${GNSSTK_INCLUDE_DIR}/gpstk"
+            INTERFACE_LINK_LIBRARIES "${GNSSTK_LIBRARY}"
+        )
+    else()
+        set_target_properties(Gnsstk::gnsstk PROPERTIES
+            IMPORTED_LINK_INTERFACE_LANGUAGES "CXX"
+            IMPORTED_LOCATION "${GNSSTK_LIBRARY}"
+            INTERFACE_INCLUDE_DIRECTORIES "${GNSSTK_INCLUDE_DIR};${GNSSTK_INCLUDE_DIR}/gnsstk"
+            INTERFACE_LINK_LIBRARIES "${GNSSTK_LIBRARY}"
+        )
+    endif()
 endif()
 
-mark_as_advanced(GNSSTK_LIBRARY GNSSTK_INCLUDE_DIR)
+mark_as_advanced(GNSSTK_LIBRARY GNSSTK_INCLUDE_DIR GNSSTK_USES_GPSTK_NAMESPACE GNSSTK_OLDER_THAN_8)
diff --git a/cmake/Modules/FindGPSTK.cmake b/cmake/Modules/FindGPSTK.cmake
deleted file mode 100644
index 5ea1beb54..000000000
--- a/cmake/Modules/FindGPSTK.cmake
+++ /dev/null
@@ -1,99 +0,0 @@
-# GNSS-SDR is a Global Navigation Satellite System software-defined receiver.
-# This file is part of GNSS-SDR.
-#
-# SPDX-FileCopyrightText: 2011-2020 C. Fernandez-Prades cfernandez(at)cttc.es
-# SPDX-License-Identifier: BSD-3-Clause
-
-# - Find gpstk library
-# Find the native gpstk includes and library
-# This module defines
-#  GPSTK_INCLUDE_DIR, where to find Rinex3ObsBase.hpp, etc.
-#  GPSTK_FOUND, If false, do not try to use GPSTK.
-#  GPSTK_LIBRARY, where to find the GPSTK library.
-#
-# Provides the following imported target:
-# Gpstk::gpstk
-#
-
-if(NOT COMMAND feature_summary)
-    include(FeatureSummary)
-endif()
-
-if(NOT GPSTK_ROOT)
-    set(GPSTK_ROOT_USER_DEFINED /usr/local)
-else()
-    set(GPSTK_ROOT_USER_DEFINED ${GPSTK_ROOT})
-endif()
-if(DEFINED ENV{GPSTK_ROOT})
-    set(GPSTK_ROOT_USER_DEFINED
-        ${GPSTK_ROOT_USER_DEFINED}
-        $ENV{GPSTK_ROOT}
-    )
-endif()
-
-find_path(GPSTK_INCLUDE_DIR gpstk/Rinex3ObsBase.hpp
-    PATHS ${GPSTK_ROOT_USER_DEFINED}/include
-          /usr/include
-          /usr/local/include
-          /opt/local/include
-)
-
-set(GPSTK_NAMES gpstk libgpstk)
-
-include(GNUInstallDirs)
-
-find_library(GPSTK_LIBRARY NAMES ${GPSTK_NAMES}
-    PATHS ${GPSTK_ROOT_USER_DEFINED}/lib
-          ${GPSTK_ROOT_USER_DEFINED}/${CMAKE_INSTALL_LIBDIR}
-          /usr/local/lib
-          /usr/${CMAKE_INSTALL_LIBDIR}
-          /usr/local/${CMAKE_INSTALL_LIBDIR}
-          /opt/local/lib
-)
-
-# handle the QUIET and REQUIRED arguments and set GPSTK_FOUND to TRUE if
-# all listed variables are TRUE
-include(FindPackageHandleStandardArgs)
-find_package_handle_standard_args(GPSTK DEFAULT_MSG GPSTK_LIBRARY GPSTK_INCLUDE_DIR)
-
-if(GPSTK_FOUND)
-    set(OLD_PACKAGE_VERSION ${PACKAGE_VERSION})
-    unset(PACKAGE_VERSION)
-    if(EXISTS ${CMAKE_INSTALL_FULL_DATADIR}/cmake/GPSTK/GPSTKConfigVersion.cmake)
-        include(${CMAKE_INSTALL_FULL_DATADIR}/cmake/GPSTK/GPSTKConfigVersion.cmake)
-    endif()
-    if(PACKAGE_VERSION)
-        set(GPSTK_VERSION ${PACKAGE_VERSION})
-    endif()
-    set(PACKAGE_VERSION ${OLD_PACKAGE_VERSION})
-endif()
-
-if(GPSTK_FOUND AND GPSTK_VERSION)
-    set_package_properties(GPSTK PROPERTIES
-        DESCRIPTION "Library and suite of applications for satellite navigation (found: v${GPSTK_VERSION})"
-    )
-else()
-    set_package_properties(GPSTK PROPERTIES
-        DESCRIPTION "Library and suite of applications for satellite navigation"
-    )
-endif()
-
-if(GPSTK_FOUND AND NOT EXISTS ${GPSTK_INCLUDE_DIR}/gpstk/SatelliteSystem.hpp)
-    set(GPSTK_OLDER_THAN_8 TRUE)
-endif()
-
-set_package_properties(GPSTK PROPERTIES
-    URL "https://github.com/SGL-UT/gnsstk"
-)
-
-if(GPSTK_FOUND AND NOT ENABLE_OWN_GPSTK AND NOT TARGET Gpstk::gpstk)
-    add_library(Gpstk::gpstk SHARED IMPORTED)
-    set_target_properties(Gpstk::gpstk PROPERTIES
-        IMPORTED_LINK_INTERFACE_LANGUAGES "CXX"
-        IMPORTED_LOCATION "${GPSTK_LIBRARY}"
-        INTERFACE_INCLUDE_DIRECTORIES "${GPSTK_INCLUDE_DIR};${GPSTK_INCLUDE_DIR}/gpstk"
-        INTERFACE_LINK_LIBRARIES "${GPSTK_LIBRARY}"
-    )
-endif()
-
-mark_as_advanced(GPSTK_LIBRARY GPSTK_INCLUDE_DIR)
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index be0d63cb7..31dfb3ca7 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -35,6 +35,13 @@ All notable changes to GNSS-SDR will be documented in this file.
   **not** applied to the computed PVT solution. In the Galileo E6B-only
   receiver, HAS messages are decoded and reported.
 
+### Improvements in Maintainability:
+
+- The now archived [GPSTk toolkit](https://github.com/SGL-UT/GPSTk), used in
+  some optional tests and applications, has been replaced by the new
+  [GNSSTk](https://github.com/SGL-UT/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`
diff --git a/src/tests/CMakeLists.txt b/src/tests/CMakeLists.txt
index 238e9074d..9c0e34762 100644
--- a/src/tests/CMakeLists.txt
+++ b/src/tests/CMakeLists.txt
@@ -555,9 +555,12 @@ if(ENABLE_UNIT_TESTING)
     endif()
     if(ENABLE_UNIT_TESTING_EXTRA)
         target_link_libraries(run_tests PRIVATE Gnsstk::gnsstk)
-        #if(GNSSTK_OLDER_THAN_8)
-        #    target_compile_definitions(run_tests PRIVATE -DOLD_GPSTK=1)
-        #endif()
+        if(GNSSTK_OLDER_THAN_8)
+            target_compile_definitions(run_tests PRIVATE -DOLD_GPSTK=1)
+        endif()
+        if(GNSSTK_USES_GPSTK_NAMESPACE)
+            target_compile_definitions(run_tests PRIVATE -DGNSSTK_USES_GPSTK_NAMESPACE=1)
+        endif()
     endif()
     if(ENABLE_STRIP)
         set_target_properties(run_tests PROPERTIES LINK_FLAGS "-s")
diff --git a/src/tests/data/gpstk_static.patch b/src/tests/data/gpstk_static.patch
deleted file mode 100644
index bfddec0e2..000000000
--- a/src/tests/data/gpstk_static.patch
+++ /dev/null
@@ -1,31 +0,0 @@
-SPDX-License-Identifier: GPL-3.0-or-later
-SPDX-FileCopyrightText: 2020 Carles Fernandez-Prades <carles.fernandez@cttc.es>
---- CMakeLists.txt	2022-04-05 23:24:04.000000000 +0200
-+++ CMakeLists.txt	2022-04-05 23:29:02.000000000 +0200
-@@ -77,7 +77,16 @@
-
-
- include( BuildSetup.cmake )
--
-+set(STADYN "STATIC")
-+if(POLICY CMP0063)
-+    cmake_policy(SET CMP0063 NEW)
-+    set(CMAKE_CXX_VISIBILITY_PRESET hidden)
-+    set(CMAKE_VISIBILITY_INLINES_HIDDEN 1)
-+else()
-+    if((CMAKE_CXX_COMPILER_ID MATCHES "Clang" OR CMAKE_CXX_COMPILER_ID STREQUAL "GNU") AND NOT WIN32)
-+        add_definitions(-fvisibility=hidden)
-+    endif()
-+endif()
- #============================================================
- # Core Library Target Files
- #============================================================
-@@ -161,7 +170,7 @@
- add_library( gpstk ${STADYN} ${GPSTK_SRC_FILES} ${GPSTK_INC_FILES} )
-
- # GPSTk library install target
--install( TARGETS gpstk DESTINATION "${CMAKE_INSTALL_LIBDIR}" EXPORT "${EXPORT_TARGETS_FILENAME}" )
-+install( TARGETS gpstk DESTINATION lib EXPORT "${EXPORT_TARGETS_FILENAME}" )
-
- # GPSTk header file install target (whether it is version dependent changes based on user flag)
- install( FILES ${GPSTK_INC_FILES} DESTINATION ${CMAKE_INSTALL_INCLUDEDIR} )
diff --git a/src/tests/unit-tests/signal-processing-blocks/observables/hybrid_observables_test.cc b/src/tests/unit-tests/signal-processing-blocks/observables/hybrid_observables_test.cc
index 493941408..704005402 100644
--- a/src/tests/unit-tests/signal-processing-blocks/observables/hybrid_observables_test.cc
+++ b/src/tests/unit-tests/signal-processing-blocks/observables/hybrid_observables_test.cc
@@ -57,11 +57,6 @@
 #include <gnuradio/blocks/null_sink.h>
 #include <gnuradio/filter/firdes.h>
 #include <gnuradio/top_block.h>
-#include <gpstk/Rinex3ObsBase.hpp>
-#include <gpstk/Rinex3ObsData.hpp>
-#include <gpstk/Rinex3ObsHeader.hpp>
-#include <gpstk/Rinex3ObsStream.hpp>
-#include <gpstk/RinexUtilities.hpp>
 #include <gtest/gtest.h>
 #include <matio.h>
 #include <pmt/pmt.h>
@@ -70,6 +65,20 @@
 #include <exception>
 #include <unistd.h>
 #include <utility>
+#if GNSSTK_USES_GPSTK_NAMESPACE
+#include <gpstk/Rinex3ObsBase.hpp>
+#include <gpstk/Rinex3ObsData.hpp>
+#include <gpstk/Rinex3ObsHeader.hpp>
+#include <gpstk/Rinex3ObsStream.hpp>
+#include <gpstk/RinexUtilities.hpp>
+namespace gnsstk = gpstk;
+#else
+#include <gnsstk/Rinex3ObsBase.hpp>
+#include <gnsstk/Rinex3ObsData.hpp>
+#include <gnsstk/Rinex3ObsHeader.hpp>
+#include <gnsstk/Rinex3ObsStream.hpp>
+#include <gnsstk/RinexUtilities.hpp>
+#endif
 
 #if HAS_GENERIC_LAMBDA
 #else
@@ -1556,17 +1565,17 @@ bool HybridObservablesTest::ReadRinexObs(std::vector<arma::mat>* obs_vec, Gnss_S
     // Open and read reference RINEX observables file
     try
         {
-            gpstk::Rinex3ObsStream r_ref(FLAGS_filename_rinex_obs);
+            gnsstk::Rinex3ObsStream r_ref(FLAGS_filename_rinex_obs);
             r_ref.exceptions(std::ios::failbit);
-            gpstk::Rinex3ObsData r_ref_data;
-            gpstk::Rinex3ObsHeader r_ref_header;
+            gnsstk::Rinex3ObsData r_ref_data;
+            gnsstk::Rinex3ObsHeader r_ref_header;
 
-            gpstk::RinexDatum dataobj;
+            gnsstk::RinexDatum dataobj;
 
             r_ref >> r_ref_header;
 
             std::vector<bool> first_row;
-            gpstk::SatID prn;
+            gnsstk::SatID prn;
             for (unsigned int n = 0; n < gnss_synchro_vec.size(); n++)
                 {
                     first_row.push_back(true);
@@ -1582,28 +1591,28 @@ bool HybridObservablesTest::ReadRinexObs(std::vector<arma::mat>* obs_vec, Gnss_S
                                 {
                                 case 'G':
 #if OLD_GPSTK
-                                    prn = gpstk::SatID(myprn, gpstk::SatID::systemGPS);
+                                    prn = gnsstk::SatID(myprn, gnsstk::SatID::systemGPS);
 #else
-                                    prn = gpstk::SatID(myprn, gpstk::SatelliteSystem::GPS);
+                                    prn = gnsstk::SatID(myprn, gnsstk::SatelliteSystem::GPS);
 #endif
                                     break;
                                 case 'E':
 #if OLD_GPSTK
-                                    prn = gpstk::SatID(myprn, gpstk::SatID::systemGalileo);
+                                    prn = gnsstk::SatID(myprn, gnsstk::SatID::systemGalileo);
 #else
-                                    prn = gpstk::SatID(myprn, gpstk::SatelliteSystem::Galileo);
+                                    prn = gnsstk::SatID(myprn, gnsstk::SatelliteSystem::Galileo);
 #endif
                                     break;
                                 default:
 #if OLD_GPSTK
-                                    prn = gpstk::SatID(myprn, gpstk::SatID::systemGPS);
+                                    prn = gnsstk::SatID(myprn, gnsstk::SatID::systemGPS);
 #else
-                                    prn = gpstk::SatID(myprn, gpstk::SatelliteSystem::GPS);
+                                    prn = gnsstk::SatID(myprn, gnsstk::SatelliteSystem::GPS);
 #endif
                                 }
 
-                            gpstk::CommonTime time = r_ref_data.time;
-                            double sow(static_cast<gpstk::GPSWeekSecond>(time).sow);
+                            gnsstk::CommonTime time = r_ref_data.time;
+                            double sow(static_cast<gnsstk::GPSWeekSecond>(time).sow);
 
                             auto pointer = r_ref_data.obs.find(prn);
                             if (pointer == r_ref_data.obs.end())
@@ -1680,12 +1689,12 @@ bool HybridObservablesTest::ReadRinexObs(std::vector<arma::mat>* obs_vec, Gnss_S
                         }
                 }  // end while
         }          // End of 'try' block
-    catch (const gpstk::FFStreamError& e)
+    catch (const gnsstk::FFStreamError& e)
         {
             std::cout << e;
             return false;
         }
-    catch (const gpstk::Exception& e)
+    catch (const gnsstk::Exception& e)
         {
             std::cout << e;
             return false;
diff --git a/src/tests/unit-tests/signal-processing-blocks/observables/hybrid_observables_test_fpga.cc b/src/tests/unit-tests/signal-processing-blocks/observables/hybrid_observables_test_fpga.cc
index 9e40ab53c..74e397d2e 100644
--- a/src/tests/unit-tests/signal-processing-blocks/observables/hybrid_observables_test_fpga.cc
+++ b/src/tests/unit-tests/signal-processing-blocks/observables/hybrid_observables_test_fpga.cc
@@ -56,11 +56,6 @@
 #include <gnuradio/blocks/null_sink.h>
 #include <gnuradio/filter/firdes.h>
 #include <gnuradio/top_block.h>
-#include <gpstk/Rinex3ObsBase.hpp>
-#include <gpstk/Rinex3ObsData.hpp>
-#include <gpstk/Rinex3ObsHeader.hpp>
-#include <gpstk/Rinex3ObsStream.hpp>
-#include <gpstk/RinexUtilities.hpp>
 #include <gtest/gtest.h>
 #include <matio.h>
 #include <pmt/pmt.h>
@@ -71,6 +66,21 @@
 #include <unistd.h>
 #include <utility>
 
+#if GNSSTK_USES_GPSTK_NAMESPACE
+#include <gpstk/Rinex3ObsBase.hpp>
+#include <gpstk/Rinex3ObsData.hpp>
+#include <gpstk/Rinex3ObsHeader.hpp>
+#include <gpstk/Rinex3ObsStream.hpp>
+#include <gpstk/RinexUtilities.hpp>
+namespace gnsstk = gpstk;
+#else
+#include <gnsstk/Rinex3ObsBase.hpp>
+#include <gnsstk/Rinex3ObsData.hpp>
+#include <gnsstk/Rinex3ObsHeader.hpp>
+#include <gnsstk/Rinex3ObsStream.hpp>
+#include <gnsstk/RinexUtilities.hpp>
+#endif
+
 #if HAS_GENERIC_LAMBDA
 #else
 #include <boost/bind/bind.hpp>
@@ -1648,17 +1658,17 @@ bool HybridObservablesTestFpga::ReadRinexObs(std::vector<arma::mat>* obs_vec, Gn
     // Open and read reference RINEX observables file
     try
         {
-            gpstk::Rinex3ObsStream r_ref(FLAGS_filename_rinex_obs);
+            gnsstk::Rinex3ObsStream r_ref(FLAGS_filename_rinex_obs);
             r_ref.exceptions(std::ios::failbit);
-            gpstk::Rinex3ObsData r_ref_data;
-            gpstk::Rinex3ObsHeader r_ref_header;
+            gnsstk::Rinex3ObsData r_ref_data;
+            gnsstk::Rinex3ObsHeader r_ref_header;
 
-            gpstk::RinexDatum dataobj;
+            gnsstk::RinexDatum dataobj;
 
             r_ref >> r_ref_header;
 
             std::vector<bool> first_row;
-            gpstk::SatID prn;
+            gnsstk::SatID prn;
             for (unsigned int n = 0; n < gnss_synchro_vec.size(); n++)
                 {
                     first_row.push_back(true);
@@ -1674,28 +1684,28 @@ bool HybridObservablesTestFpga::ReadRinexObs(std::vector<arma::mat>* obs_vec, Gn
                                 {
                                 case 'G':
 #if OLD_GPSTK
-                                    prn = gpstk::SatID(myprn, gpstk::SatID::systemGPS);
+                                    prn = gnsstk::SatID(myprn, gnsstk::SatID::systemGPS);
 #else
-                                    prn = gpstk::SatID(myprn, gpstk::SatelliteSystem::GPS);
+                                    prn = gnsstk::SatID(myprn, gnsstk::SatelliteSystem::GPS);
 #endif
                                     break;
                                 case 'E':
 #if OLD_GPSTK
-                                    prn = gpstk::SatID(myprn, gpstk::SatID::systemGalileo);
+                                    prn = gnsstk::SatID(myprn, gnsstk::SatID::systemGalileo);
 #else
-                                    prn = gpstk::SatID(myprn, gpstk::SatelliteSystem::Galileo);
+                                    prn = gnsstk::SatID(myprn, gnsstk::SatelliteSystem::Galileo);
 #endif
                                     break;
                                 default:
 #if OLD_GPSTK
-                                    prn = gpstk::SatID(myprn, gpstk::SatID::systemGPS);
+                                    prn = gnsstk::SatID(myprn, gnsstk::SatID::systemGPS);
 #else
-                                    prn = gpstk::SatID(myprn, gpstk::SatelliteSystem::GPS);
+                                    prn = gnsstk::SatID(myprn, gnsstk::SatelliteSystem::GPS);
 #endif
                                 }
 
-                            gpstk::CommonTime time = r_ref_data.time;
-                            double sow(static_cast<gpstk::GPSWeekSecond>(time).sow);
+                            gnsstk::CommonTime time = r_ref_data.time;
+                            double sow(static_cast<gnsstk::GPSWeekSecond>(time).sow);
 
                             auto pointer = r_ref_data.obs.find(prn);
                             if (pointer == r_ref_data.obs.end())
@@ -1773,12 +1783,12 @@ bool HybridObservablesTestFpga::ReadRinexObs(std::vector<arma::mat>* obs_vec, Gn
                 }  // end while
         }          // End of 'try' block
 
-    catch (const gpstk::FFStreamError& e)
+    catch (const gnsstk::FFStreamError& e)
         {
             std::cout << e;
             return false;
         }
-    catch (const gpstk::Exception& e)
+    catch (const gnsstk::Exception& e)
         {
             std::cout << e;
             return false;
diff --git a/src/utils/rinex-tools/CMakeLists.txt b/src/utils/rinex-tools/CMakeLists.txt
index 5ba60ae5c..0071bf3dc 100644
--- a/src/utils/rinex-tools/CMakeLists.txt
+++ b/src/utils/rinex-tools/CMakeLists.txt
@@ -10,8 +10,13 @@ if("${ARMADILLO_VERSION_STRING}" VERSION_GREATER "9.800" OR (NOT ARMADILLO_FOUND
     find_package(GNSSTK QUIET)
     if(NOT GNSSTK_FOUND OR ENABLE_OWN_GNSSTK)
         include(GNUInstallDirs)
-        set(GNSSTK_LIBRARY ${CMAKE_BINARY_DIR}/gnsstk-${GNSSSDR_GNSSTK_LOCAL_VERSION}/install/lib/${CMAKE_FIND_LIBRARY_PREFIXES}gnsstk${CMAKE_STATIC_LIBRARY_SUFFIX})
-        set(GNSSTK_INCLUDE_DIR ${CMAKE_BINARY_DIR}/gnsstk-${GNSSSDR_GNSSTK_LOCAL_VERSION}/install/include)
+        if(GNSSTK_USES_GPSTK_NAMESPACE)
+            set(GNSSTK_LIBRARY ${CMAKE_BINARY_DIR}/gnsstk-${GNSSSDR_GNSSTK_LOCAL_VERSION}/install/lib/${CMAKE_FIND_LIBRARY_PREFIXES}gnsstk${CMAKE_STATIC_LIBRARY_SUFFIX})
+            set(GNSSTK_INCLUDE_DIR ${CMAKE_BINARY_DIR}/gnsstk-${GNSSSDR_GNSSTK_LOCAL_VERSION}/install/include)
+        else()
+            set(GNSSTK_LIBRARY ${CMAKE_BINARY_DIR}/gpstk-${GNSSSDR_GNSSTK_LOCAL_VERSION}/install/lib/${CMAKE_FIND_LIBRARY_PREFIXES}gnsstk${CMAKE_STATIC_LIBRARY_SUFFIX})
+            set(GNSSTK_INCLUDE_DIR ${CMAKE_BINARY_DIR}/gpstk-${GNSSSDR_GNSSTK_LOCAL_VERSION}/install/include)
+        endif()
     endif()
 
     if(USE_CMAKE_TARGET_SOURCES)
@@ -54,17 +59,35 @@ if("${ARMADILLO_VERSION_STRING}" VERSION_GREATER "9.800" OR (NOT ARMADILLO_FOUND
     if(NOT MATIO_FOUND OR MATIO_VERSION_STRING VERSION_LESS ${GNSSSDR_MATIO_MIN_VERSION})
         add_dependencies(obsdiff matio-${GNSSSDR_MATIO_LOCAL_VERSION})
     endif()
+    if(GNSSTK_USES_GPSTK_NAMESPACE)
+        target_compile_definitions(obsdiff PUBLIC -DGNSSTK_USES_GPSTK_NAMESPACE=1)
+    endif()
+    if(GNSSTK_OLDER_THAN_8)
+        target_compile_definitions(obsdiff PUBLIC -DOLD_GPSTK=1)
+    endif()
 
     if(NOT TARGET Gnsstk::gnsstk)
-        file(MAKE_DIRECTORY ${GNSSTK_INCLUDE_DIR}/gnsstk)
-        add_library(Gnsstk::gnsstk STATIC IMPORTED)
-        add_dependencies(Gnsstk::gnsstk gnsstk-${GNSSSDR_GNSSTK_LOCAL_VERSION})
-        set_target_properties(Gnsstk::gnsstk PROPERTIES
-            IMPORTED_LINK_INTERFACE_LANGUAGES "CXX"
-            IMPORTED_LOCATION "${GNSSTK_LIBRARY}"
-            INTERFACE_INCLUDE_DIRECTORIES "${GNSSTK_INCLUDE_DIR};${GNSSTK_INCLUDE_DIR}/gnsstk"
-            INTERFACE_LINK_LIBRARIES "${GNSSTK_LIBRARY}"
-        )
+        if(GNSSTK_USES_GPSTK_NAMESPACE)
+            file(MAKE_DIRECTORY ${GNSSTK_INCLUDE_DIR}/gpstk)
+            add_library(Gnsstk::gnsstk STATIC IMPORTED)
+            add_dependencies(Gnsstk::gnsstk gnsstk-${GNSSSDR_GNSSTK_LOCAL_VERSION})
+            set_target_properties(Gnsstk::gnsstk PROPERTIES
+                IMPORTED_LINK_INTERFACE_LANGUAGES "CXX"
+                IMPORTED_LOCATION "${GNSSTK_LIBRARY}"
+                INTERFACE_INCLUDE_DIRECTORIES "${GNSSTK_INCLUDE_DIR};${GNSSTK_INCLUDE_DIR}/gpstk"
+                INTERFACE_LINK_LIBRARIES "${GNSSTK_LIBRARY}"
+            )
+        else()
+            file(MAKE_DIRECTORY ${GNSSTK_INCLUDE_DIR}/gnsstk)
+            add_library(Gnsstk::gnsstk STATIC IMPORTED)
+            add_dependencies(Gnsstk::gnsstk gnsstk-${GNSSSDR_GNSSTK_LOCAL_VERSION})
+            set_target_properties(Gnsstk::gnsstk PROPERTIES
+                IMPORTED_LINK_INTERFACE_LANGUAGES "CXX"
+                IMPORTED_LOCATION "${GNSSTK_LIBRARY}"
+                INTERFACE_INCLUDE_DIRECTORIES "${GNSSTK_INCLUDE_DIR};${GNSSTK_INCLUDE_DIR}/gnsstk"
+                INTERFACE_LINK_LIBRARIES "${GNSSTK_LIBRARY}"
+            )
+        endif()
     endif()
 
     target_link_libraries(obsdiff
diff --git a/src/utils/rinex-tools/README.md b/src/utils/rinex-tools/README.md
index 1bb198834..58a1bd259 100644
--- a/src/utils/rinex-tools/README.md
+++ b/src/utils/rinex-tools/README.md
@@ -23,8 +23,8 @@ Requirements:
 - [Gflags](https://github.com/gflags/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.
-- [GPSTK](https://github.com/SGL-UT/GPSTk): The GPS Toolkit, used for RINEX
-  files reading. If not found in your system, the latest version will be
+- [GNSSTK](https://github.com/SGL-UT/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](https://github.com/tbeu/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
diff --git a/src/utils/rinex-tools/obsdiff.cc b/src/utils/rinex-tools/obsdiff.cc
index cc03ae660..c44817551 100644
--- a/src/utils/rinex-tools/obsdiff.cc
+++ b/src/utils/rinex-tools/obsdiff.cc
@@ -21,6 +21,34 @@
 #include "gnuplot_i.h"
 #include "obsdiff_flags.h"
 #include <armadillo>
+#include <matio.h>
+#include <algorithm>
+#include <array>
+#include <fstream>
+#include <iomanip>
+#include <map>
+#include <set>
+#include <stdexcept>
+#include <string>
+#include <vector>
+
+#if GNSSTK_USES_GPSTK_NAMESPACE
+#include <gpstk/GGTropModel.hpp>
+#include <gpstk/GNSSconstants.hpp>
+#include <gpstk/GPSEphemerisStore.hpp>
+#include <gpstk/PRSolution.hpp>
+#include <gpstk/Rinex3NavData.hpp>
+#include <gpstk/Rinex3NavHeader.hpp>
+#include <gpstk/Rinex3NavStream.hpp>
+#include <gpstk/Rinex3ObsData.hpp>
+#include <gpstk/Rinex3ObsHeader.hpp>
+#include <gpstk/Rinex3ObsStream.hpp>
+#include <gpstk/RinexMetBase.hpp>
+#include <gpstk/RinexMetData.hpp>
+#include <gpstk/RinexMetHeader.hpp>
+#include <gpstk/RinexMetStream.hpp>
+namespace gnsstk = gpstk;
+#else
 // Classes for handling observations RINEX files (data)
 #include <gnsstk/Rinex3ObsData.hpp>
 #include <gnsstk/Rinex3ObsHeader.hpp>
@@ -49,16 +77,7 @@
 
 // Class defining GPS system constants
 #include <gnsstk/GNSSconstants.hpp>
-#include <matio.h>
-#include <algorithm>
-#include <array>
-#include <fstream>
-#include <iomanip>
-#include <map>
-#include <set>
-#include <stdexcept>
-#include <string>
-#include <vector>
+#endif
 
 #if GFLAGS_OLD_NAMESPACE
 namespace gflags
@@ -111,15 +130,27 @@ std::map<int, arma::mat> ReadRinexObs(const std::string& rinex_file, char system
             switch (system)
                 {
                 case 'G':
-                    prn.system = gnsstk::SatelliteSystem::GPS;
+#if OLD_GPSTK
+                    prn.system = gpstk::SatID::systemGPS;
+#else
+                    prn.system = gpstk::SatelliteSystem::GPS;
+#endif
                     PRN_set = available_gps_prn;
                     break;
                 case 'E':
-                    prn.system = gnsstk::SatelliteSystem::Galileo;
+#if OLD_GPSTK
+                    prn.system = gpstk::SatID::systemGalileo;
+#else
+                    prn.system = gpstk::SatelliteSystem::Galileo;
+#endif
                     PRN_set = available_galileo_prn;
                     break;
                 default:
-                    prn.system = gnsstk::SatelliteSystem::GPS;
+#if OLD_GPSTK
+                    prn.system = gpstk::SatID::systemGPS;
+#else
+                    prn.system = gpstk::SatelliteSystem::GPS;
+#endif
                     PRN_set = available_gps_prn;
                 }
 
@@ -1239,12 +1270,19 @@ double compute_rx_clock_error(const std::string& rinex_nav_filename, const std::
                             // pointer to the tropospheric model to be applied
                             try
                                 {
-                                    gnsstk::Matrix<double> invMC;
+#if OLD_GPSTK
+                                    std::vector<gpstk::SatID::SatelliteSystem> Syss;
+#endif
+                                    gpstk::Matrix<double> invMC;
                                     int iret;
                                     // Call RAIMCompute
+#if OLD_GPSTK
+                                    iret = raimSolver.RAIMCompute(rod.time, prnVec, Syss, rangeVec, invMC,
+                                        &bcestore, tropModelPtr);
+#else
                                     iret = raimSolver.RAIMCompute(rod.time, prnVec, rangeVec, invMC,
                                         &bcestore, tropModelPtr);
-
+#endif
                                     switch (iret)
                                         {
                                         /// @return Return values:
diff --git a/src/utils/rinex2assist/CMakeLists.txt b/src/utils/rinex2assist/CMakeLists.txt
index fa0dd40c3..d788109c7 100644
--- a/src/utils/rinex2assist/CMakeLists.txt
+++ b/src/utils/rinex2assist/CMakeLists.txt
@@ -8,8 +8,13 @@
 find_package(GNSSTK QUIET)
 if(NOT GNSSTK_FOUND OR ENABLE_OWN_GNSSTK)
     include(GNUInstallDirs)
-    set(GNSSTK_LIBRARY ${CMAKE_BINARY_DIR}/gnsstk-${GNSSSDR_GNSSTK_LOCAL_VERSION}/install/${CMAKE_INSTALL_LIBDIR}/${CMAKE_FIND_LIBRARY_PREFIXES}gnsstk${CMAKE_STATIC_LIBRARY_SUFFIX})
-    set(GNSSTK_INCLUDE_DIR ${CMAKE_BINARY_DIR}/gnsstk-${GNSSSDR_GNSSTK_LOCAL_VERSION}/install/include)
+    if(GNSSTK_USES_GPSTK_NAMESPACE)
+        set(GNSSTK_LIBRARY ${CMAKE_BINARY_DIR}/gnsstk-${GNSSSDR_GNSSTK_LOCAL_VERSION}/install/${CMAKE_INSTALL_LIBDIR}/${CMAKE_FIND_LIBRARY_PREFIXES}gpstk${CMAKE_STATIC_LIBRARY_SUFFIX})
+        set(GNSSTK_INCLUDE_DIR ${CMAKE_BINARY_DIR}/gnsstk-${GNSSSDR_GNSSTK_LOCAL_VERSION}/install/include)
+    else()
+        set(GNSSTK_LIBRARY ${CMAKE_BINARY_DIR}/gnsstk-${GNSSSDR_GNSSTK_LOCAL_VERSION}/install/${CMAKE_INSTALL_LIBDIR}/${CMAKE_FIND_LIBRARY_PREFIXES}gnsstk${CMAKE_STATIC_LIBRARY_SUFFIX})
+        set(GNSSTK_INCLUDE_DIR ${CMAKE_BINARY_DIR}/gnsstk-${GNSSSDR_GNSSTK_LOCAL_VERSION}/install/include)
+    endif()
 endif()
 
 
@@ -79,11 +84,25 @@ if(Boost_FOUND)
             core_system_parameters
     )
 
-    target_include_directories(rinex2assist
-        PRIVATE
-            ${GNSSTK_INCLUDE_DIR}/gnsstk
-            ${GNSSTK_INCLUDE_DIR}
-    )
+    if(GNSSTK_USES_GPSTK_NAMESPACE)
+        target_compile_definitions(rinex2assist PUBLIC -DGNSSTK_USES_GPSTK_NAMESPACE=1)
+        target_include_directories(rinex2assist
+            PRIVATE
+                ${GNSSTK_INCLUDE_DIR}/gpstk
+                ${GNSSTK_INCLUDE_DIR}
+        )
+    else()
+        target_include_directories(rinex2assist
+            PRIVATE
+                ${GNSSTK_INCLUDE_DIR}/gnsstk
+                ${GNSSTK_INCLUDE_DIR}
+        )
+    endif()
+    if(GNSSTK_VERSION)
+        if(GNSSTK_VERSION VERSION_LESS "9.0.0")
+            target_compile_definitions(rinex2assist PUBLIC -DGNSSTK_OLDER_THAN_9=1)
+        endif()
+    endif()
 
     if(NOT UNCOMPRESS_EXECUTABLE-NOTFOUND)
         target_compile_definitions(rinex2assist PRIVATE -DUNCOMPRESS_EXECUTABLE="${UNCOMPRESS_EXECUTABLE}")
diff --git a/src/utils/rinex2assist/main.cc b/src/utils/rinex2assist/main.cc
index 0e16560cf..b394abfa0 100644
--- a/src/utils/rinex2assist/main.cc
+++ b/src/utils/rinex2assist/main.cc
@@ -28,14 +28,23 @@
 #include <boost/iostreams/filtering_streambuf.hpp>
 #include <boost/serialization/map.hpp>
 #include <gflags/gflags.h>
+#include <cstddef>  // for size_t
+#include <cstdlib>
+#include <iostream>
+#if GNSSTK_USES_GPSTK_NAMESPACE
+#include <gpstk/GALWeekSecond.hpp>
+#include <gpstk/GPSWeekSecond.hpp>
+#include <gpstk/Rinex3NavData.hpp>
+#include <gpstk/Rinex3NavHeader.hpp>
+#include <gpstk/Rinex3NavStream.hpp>
+namespace gnsstk = gpstk;
+#else
 #include <gnsstk/GALWeekSecond.hpp>
 #include <gnsstk/GPSWeekSecond.hpp>
 #include <gnsstk/Rinex3NavData.hpp>
 #include <gnsstk/Rinex3NavHeader.hpp>
 #include <gnsstk/Rinex3NavStream.hpp>
-#include <cstddef>  // for size_t
-#include <cstdlib>
-#include <iostream>
+#endif
 
 #if GFLAGS_OLD_NAMESPACE
 namespace gflags
@@ -178,12 +187,17 @@ int main(int argc, char** argv)
                     gps_utc_model.valid = (hdr.valid > 2147483648) ? true : false;
                     gps_utc_model.A1 = hdr.mapTimeCorr["GPUT"].A0;
                     gps_utc_model.A0 = hdr.mapTimeCorr["GPUT"].A1;
+#if GNSSTK_OLDER_THAN_9
+                    gps_utc_model.tot = hdr.mapTimeCorr["GPUT"].refSOW;
+                    gps_utc_model.WN_T = hdr.mapTimeCorr["GPUT"].refWeek;
+#else
                     if (hdr.mapTimeCorr["GPUT"].refTime != gnsstk::CommonTime::BEGINNING_OF_TIME)
                         {
                             gnsstk::GPSWeekSecond gws(hdr.mapTimeCorr["GPUT"].refTime);
                             gps_utc_model.tot = gws.getSOW();
                             gps_utc_model.WN_T = gws.getWeek();
                         }
+#endif
                     gps_utc_model.DeltaT_LS = hdr.leapSeconds;
                     gps_utc_model.WN_LSF = hdr.leapWeek;
                     gps_utc_model.DN = hdr.leapDay;
@@ -205,12 +219,17 @@ int main(int argc, char** argv)
                     gal_utc_model.A0 = hdr.mapTimeCorr["GAUT"].A0;
                     gal_utc_model.A1 = hdr.mapTimeCorr["GAUT"].A1;
                     gal_utc_model.Delta_tLS = hdr.leapSeconds;
+#if GNSSTK_OLDER_THAN_9
+                    gal_utc_model.tot = hdr.mapTimeCorr["GAUT"].refSOW;
+                    gal_utc_model.WNot = hdr.mapTimeCorr["GAUT"].refWeek;
+#else
                     if (hdr.mapTimeCorr["GAUT"].refTime != gnsstk::CommonTime::BEGINNING_OF_TIME)
                         {
                             gnsstk::GPSWeekSecond gws(hdr.mapTimeCorr["GAUT"].refTime);
                             gal_utc_model.tot = gws.getSOW();
                             gal_utc_model.WNot = gws.getWeek();
                         }
+#endif
                     gal_utc_model.WN_LSF = hdr.leapWeek;
                     gal_utc_model.DN = hdr.leapDay;
                     gal_utc_model.Delta_tLSF = hdr.leapDelta;