gLAB is a software tool suite developed under an European Space Agency (ESA) Contract by the research group of Astronomy and Geomatics (gAGE) from the Universitat Politecnica de Catalunya (UPC), is an interactive educational multipurpose package to process and analyse GNSS data.

gLAB performs precise modeling of GNSS observables (pseudorange and carrier phase) at the centimetre level, allowing both standalone GPS positioning and PPP. Every single error contributor may be assessed independently, which, in turn, provides a major educational benefit. gLAB is adapted to a variety of standard formats like RINEX-3.00, SP3, ANTEX and SINEX files, among others. Moreover, functionality is also included for GPS, Galileo and GLONASS, allowing performing some data analysis with real multi-constellation data.

The gLAB software tool is quite flexible, able to run under Linux, Windows, and Mac operating systems and is provided free of charge by ESA Education Office to universities and GNSS professionals.

Found on https://gssc.esa.int/navipedia/index.php/GNSS:Tools

Reference points in Austria where the accuracy of GNSS receivers can be checked.

Article describing the state of dual-frequency GNSS reception on Android devices as of 2018-06.

uBlox NEO-M8T Reference Board with SMA antenna connectors for your RTK systems, UAV systems, Robots, RC, FPV or other projects. Ultra small and light.

Accelerating GNSS Software Receivers

Fernández-Prades, Carles; Arribas, Javier; Closas, Pau

This paper addresses both the efficiency and the portability of a computer program in charge of the baseband signal processing
of a GNSS receiver.

Has Galileo-capable receiver using uBlox {LEA,MAX,NEO}-M8[S] modules.

Module with uBlox NEO-M8T and antenna.

Show the visibility of GNSS satellites.
See https://github.com/taroz/GNSS-Radar for source and options which can be passed via the URL.

Wiki page of a project designing an open-source GNSS receiver.