The first chapter of bachelor thesis is focused on theoretical explanation of the most important terms in Global Positioning System describing basic principles and position monitoring possibilities. The structure of the whole GPS system and its position setting accuracy is described further. The NMEA protocol used for transferring GPS information is shortly mentioned too. The second chapter deals with Open AT platform used for application development. It is a product of Wavecom company. The third thematic unit has already practical character. It shows the results of locating GenLoc25 modem by AT commands and decoding NMEA frame. Three variants of applications developed in Microsoft Visual C++ are described in the last chapter. All of them a...