A brief introduction to GNSS-SDR, a free and open source Global Navigation Satellite System software-defined receiver.
Here you will find:
Configuring and managing a network of connected signal processing blocks from the signal source up to the position fix.
In addition, there is a set of tutorials providing more information in particular topics or examples of use:
Description of the available GNSS-SDR configuration options at bulding time.
… and many more!