The GPS system is the most extended satellite-based navigation system nowadays, it is increasingly being used for a wide range of applications and by a huge number of users worldwide. The aim of this project is develop a set of graphical user interfaces to track the GPS satellite constellation, also called GPS Space Segment. The information of the GPS satellites is acquired, processed and stored at the IT Monitoring Station, which becomes the starting point of this project. First of all, to a better comprehension of the work realized, it is described the essentials concepts of the GPS system. Also a study of the the characteristics of the IT Monitoring Station and its functionalities has been done. To complete this theoretical approach, a look to the state of the art of the navigation systems is done. Four applications have been developed in the context of this project, an application consists on both, a server and client side. In each application it is monitored a di erent concept related with the GPS satellites: elevation and azimuth, ephemeris data and the satellites position into 2D and 3D views. In this report it is described in detail the monitored data, the applications functionalities and its internal structure. The servers have been written in C and are running, as independent processes, in the IT Monitoring Station computer. The clients have been developed with Matlab, an environment that ful lls all the GUIs needs. They are standalone applications that can run in Windows OS. Furthermore, some tests have been done to check that the performance of the applications was correct. Also this report includes some applications manuals that explain everything that an user should know in order to run and use the applications. The result of this project is four tracking applications of the GPS Space Segment.