Precision GPS means achieving position accuracies of centimeters instead of the more typical meter results of standard consumer-grade GPS. This is done by taking advantage of the carrier phase information from the reciever in addition to the pseudorange measurements. Traditionally this kind of accuracy has only been available from survey-grade receivers costing many thousands of dollars. With recent technology improvements, however, this capability has started to become possible using receivers costing less than $100. Uses for high accuracy positioning include surveying, mapping, drones, precision agriculture, marine navigation, construction, open-sky warehouse management and sports feedback.

There are only a few companies offering low-cost GPS receivers with access to the raw measurements necessary for calculating precision solutions. Some of the lowest cost and most popular single frequency options are from u-blox . They are a well established company that also provides easy-to-use free evaluation tools useful for configuration and testing of their receivers and complete documentation.   For those interested in dual frequency receivers, good low-cost options are available from SwiftNav, ComNav, and Tersus, among others.

This site offers information, resources, and tutorials for the users of low cost precision GPS. Tutorials for those just getting started with RTKLIB or low-cost GNSS are in the the “How To” section. I have documented my experience with RTKLIB and many of the low cost receivers in the blog section. The demo5 version of RTKLIB, optimized for low-cost receivers, is available in the download section, along with many raw data sets.

RTKLIB is an open source software package written by Tomoji Takasu from the Tokyo University of Marine Science and Technology. Using GNSS raw data, it is possible to run real-time or post-processing solutions to accurately determine relative position using differential information from two receivers (RTK/PPK) or absolute position from a single receiver (PPP).  The software supports all major satellite constellations (GPS, GLONASS, Galileo, BeiDou, SBAS, QZSS) and major file exchange formats. The toolkit runs with a GUI on Windows and command line tools on Linux.  It is a fantastic resource, but the official version can sometimes feel like more of an academic toolbox than a practical engineering tool.