Background:
My plan is to create a (front axle steered) rover applying ArduRover 4.0 stack, Mission planner GCS software and Pixhawk1 flight controller. As I need positioning accuracy better than 0.5 meters (10 cm would be nice), I presumably need some kind of RTK correction. Reach M+ seems to be an affordable solution.
Needless to say, I’m total newbie so all information is new to me. I went through all documents about using Reach+ with NTRIP feature, but wasn’t able to grasp the one simple picture of the equipment I must obtain.
Questions:
Considering NTRIP (DGNSS) is available, do I need more than one Reach M+ unit and it’s GPS antenna to use RTK?
Will there be need for base unit at all?
Should Pixhawk unit be equipped with another GPS unit or this Reach M+ unit solely?
What kind of telemetry radios I can use or is there need for any Reach M+ related telemetry between the rover and ground control station?
Extra wish (humbly):
A clear connection chart would be very nice, showing unambiguously all the gadgets and their connections needed here. I know quite every unit can be connected through various ports, but I’m feeling lucky that someone knows the best one
To get the accuracy of RTK, a base and a rover is required. The rover corrects its own position by using the RTCM3 ‘corrections’ stream that comes from the base in ‘real time’, which implies you that have a live communication link between the base and rover. That communication link is commonly achieved with a radio or a mobile Internet connection.
If you were only taking position measurements, rather than making movement decisions based on current position, then you could avoid the need for a communication link and do PPK instead of RTK. The land-survey equivalent: collecting points = PPK (or RTK); staking out points = RTK. I believe you were already clear on this, but your requirement for ‘steering’ is like ‘staking out’ and both require RTK mode, and the implied communication link with the base station.
Now, you can operate your own base station that is usually set over a ‘known point’ and located somewhere in the general area; OR, you can get your base corrections from a permanent base station that is maybe back at your office, or one that is operated by a third-party. This is where an NTRIP caster is used. It pulls in corrections from the base station and makes it easy for your rover to connect and receive those base corrections via the Internet. note: NTRIP may provide corrections from a real base station or from a ‘virtual’ base station. A virtual base station is just a simulated base station which is computed out of data received from several real base stations.
With that information, your answers are:
#1 You need a Reach device with GNSS (GPS) antenna, plus a communications link to a base station.
#2 With RTK, there is always a need for a base station, but you don’t have to bring your own base station to the work site if your rover is able to receive base corrections from elsewhere (e.g. Internet access and connection to an NTRIP caster)
One note: Reach RS2 has a built-in cellular modem and using that mobile Internet connection, it can operate as a true ''network rover." If you use a different Reach device (e.g. M+,M2,RS+), then you must have a Wi-Fi access point nearby that provide Internet access to your Reach devices (e.g. your smartphone acting as a Wi-Fi hotspot)
