Open-source GNSS + inertial navigation, sensor fusion simulator.  Motion trajectory generator, sensor models, and navigation 

MIT License

gnss-ins-sim

GNSS-SDR, an open-source software-defined GNSS receiver

GNU General Public License v3.0

gnss-sdr

The #1 open-source Android GNSS/GPS test program

Apache License 2.0

gpstest

Precise localization based on GNSS and IMU.

BSD 3-Clause "New" or "Revised" License

eagleye

ROS driver for NovAtel GPS / GNSS receivers

novatel_gps_driver

:blue_book: ROS/ROS2 driver for SwiftNav Duro Inertial GPS / GNSS receivers

duro_gps_driver

A version of RTKLIB optimized for low cost GNSS receivers, especially u-blox receivers.  It is based on RTKLIB 2.4.3 and is kept reasonably closely synced to that branch.  This software is provided “AS IS” without any warranties of any kind so please be careful, especially if using it in any kind of real-time application.