Development of the low-cost RTK-GPS receiver with an open source program package RTKLIB

RTKLIB is an open source program package for RTK-GPS developed by the authors. RTKLIB is a compact and portable program library written in C to provide a standard platform for RTK-GPS applications. The library implements fundamental navigation functions and carrier-based relative positioning algorithms for RTK-GPS with integer ambiguity resolution by LAMBDA. RTKLIB also supports data communication via serial I/O, TCP/IP connection and NTRIP, and various data formats including RTCM 2.3, RTCM 3.1 and proprietary raw messages for some GPS receivers. By supporting RTCM and NTRIP, NRTK (Network RTK) service can be used with RTKLIB. From the version 2.2.0, RTKLIB has been distributed under the GPLv3 license. RTKLIB was originally implemented on Windows PC. In this study, we port RTKLIB to a small and compact single-board computer BeagleBoard and construct a low-cost RTK-GPS receiver with RTKLIB. BeagleBoard has 600MHz ARM Cotex-A8 core CPU and supports embedded Linux environment. In order to acquire and track GPS signals, we employ a single-frequency GPS receiver module LEA-4T provided by u-blox AG. The RTK-GPS server running on BeagleBoard inputs the u-blox raw binary data messages. The server also inputs the base-station data via a serial port or USB network device and computes RTK-GPS solution in real-time. The total cost of the developed RTK-GPS receiver was about $400. To demonstrate and verify the performance of the low-cost RTK-GPS receiver, we made some field tests. In these tests, CPU/memory usage, accuracy of solutions and fixing ratio were evaluated. According to the test results, even with such a low-cost RTK-GPS receiver, we can obtain reasonable performance in company with RTKLIB.