Hi. We’ve successfully tested a single SparkFun GPS-RTK-SMA Breakout-ZED-F9P using one as a Base and one as a Rover. RTCM correction data was sent over a cable. The units were about 75 feet apart.
We now want to test the system using about 10 Rovers and 1 base. For now we are keeping the Rovers stationary and are fine with using a wired solution again or short range radio if that’s easier. Does any one have a suggestion for the best approach? We are also thinking of using a 10 port USB hub plugged into a laptop to gather data from each Rover.
Longer term the RTCM data will need to wireless to the nearby Base. Can a single ZED-F9P Base readily broadcast correction data to a group of 10 Rovers? Do the Rover’s just “listen” or is there any back and forth communication RX/TX across the RTCM connection?
I’ve seen people use up to 4 without any issues; I believe this should still work perform as expected - please report back your findings if/when you test it out!
You are correct, the rovers are ‘fed’ RTCM. They are listening. A rover does not need to do anything with RTCM except absorb it (no need for 2 way comm).
Assuming you can find “broadcast” radio modems, one base station can, in theory, feed an infinite number of rovers. The challenge is finding a radio modem that does not use/require an ‘ack’. For example, the HolyBro radios that we carry work great, but they are meant to work in pairs because one radio ‘acks’ back to the transmitter once a packet is successfully received. If you have multiple receivers, they will transmit an ack each, and the transmitter can get confused.
For now, my recommendation would be to look into NTRIP. This is not ideal, and way overkill for your application, but NTRIP was designed specifically to support this scenario: one ‘caster’ (the base) and multiple ‘clients’ (the rovers).