Cascade is a Linux based GPS (Global Positioning System) receiver that is incredibly flexible. Core aspects of a GPS receiver, like the RF section that down converts the signals are implemented in hardware, while all slow computations: tracking of satellites, computation of a navigation solution, etc. are preformed in software. Currently, we are using RTLinux to obtain the realtime environment required of a GPS receiver. The system is running RedHat Linux 6.2 on a 400MHz Pentium II. The hardware consists of a GPS chipset by Mitel (formerly by GEC Plessey) on an ISA card (known as the GPS Builder-2). This chipset is the industry and research standard GP2021 correlator and GP2015 RF front end, both of which are manufactored by Mitel
Beyond the use of real-time extensions, we've implemented a GUI using Qt (www.trolltech.com) to display suitable information related to GPS (current position, average position over time, satellite information, etc.) Also, the Qt environment allows for an incredible array of graphical possibilites. Thus, it is possible to plot the user position error in real-time, satellite positions, 3-D position wanderings.... Note that the GUI interface of the receiver is deemed open source (under a GPL license). Furthermore, I've thrown together an ncurses version of the interface and a simple java applet.
Another major advantage of Cascade is that it's possible to remotely (over the internet, per se) connect to a server running the GPS core code and monitor the receiver's operation, control its operating parameters, remotely log data, etc..