If we know the second to second issues within our local vicinity, a RTCM capable receiver can correct the location solution with great precision. Earth's gravitational field is not uniform so relativistic effects can add inaccuracies. Geomagnetic storms cause slight timing delays increasing the location error. A lot can happen to the signal from the GPS satellites to you across that distance. Remember, the GPS satellites are very far away about 20,000km or 12,000 miles away. Each RTCM message contains details about the GPS/GNSS network, and perturbations in the ionosphere and troposphere. Each message type has a different length but as a rule of thumb it's a couple hundred bytes every second. There are a few different types of messages but the ones we care about are numbers 1005, 1077, 1087, and 1230. Instead you simply pass the bytes to the GPS receiver and it will parse the correction data. The contents of RTCM frames can be decoded but you, the user, rarely need to. In these tutorials we will be focusing on real time (RTK) capable receivers.įrom Review of GNSS Formats for Real-Time Positioning and Geo++ It's also possible to tether a lower cost receiver (such as the NEO-M8T) to a laptop and run RTKLIB in unison and achieve real time solutions but this is a rather large, power hungry setup that is not ideal for embedded mobile applications. This is handy for applications like aerial photography and agricultural inspection were alignment is important after the fact. The precision is 0.1mm!ġ cm accuracy is also possible with a few lower cost receivers (such as the NEO-M8T) by capturing raw streams from the GPS satellites and then post processing the logs with an open source program called RTKLIB. To be clear, it’s not 1cm precision it's 1cm accuracy. Once it's all setup and working, the rover GPS module will output normal NMEA sentences but with really accurate lat and long. LoRa and LTE-CAT M1 are superb choices for this backhaul. This usually comes from an internet connection or a long distance radio capable of approximately 500 bytes per second. You’ll also need a source of RTCM correction data. You'll need a GPS receiver capable of receiving and incorporating the RTCM correction data into its location solution. Did You Say 1 cm? Zomg How Do I Get 1 cm Accuracy!?

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