The goal of the GPS Toolkit project is to provide an open source library and suite of applications to the satellite navigation community--to free researchers to focus on research, not lower level coding. GPS users employ practically every computational architecture and operating system. Therefore the design of the GPSTk suite is as platform-independent as possible. Platform independence is achieved through use of the ISO-standard C programming language. The principles of object-oriented programming are used throughout the GPSTk code base in order to ensure that the code is modular, extensible and maintainable.