A teaser from Michael Oborne, showing impressive precision. Using a Septentrio asterx-m and a HX-CH4601A. Full details coming soon to the APM wiki
Michael, like Jesus A. said the rover costs around 5K. I don't have experience with using a normal Survey Grade GPS as base station. We don't use a local base station. We use NTRIP, in Belgium different reference stations are spread and they send correction data (RTCM) to our laptops.
here is a video of the setup I used.
@Jesus, the main problem with NMEA is that the clear text is very inefficient. Limiting how fast you can send updates on serial. Also, many GPS manufacturers will offer more data/options from the GPS outside what is covered by the NMEA standard.
NMEA is supported by all GPS RTK solutions out there ans it is the first option that should work 100% with APM IMHO.
I have not tested it yet but I will do it (we are too developing a L1/L2/GLONASS solution). However I have read many times in drones-discuss that NMEA GPS produces glitches in navigation with APM compared to the ublox ones.
I know it has extended messages and that it does not provide as much info as a propietary protocol but it is a standard and THAT alone is important.
With just the GGA NMEA message we have information about the type of solution being reported. RTK, Single, etc.
@Chris, thanks for sharing and well done Michael.
@Mike Papenhagen, hi, trust all is well. You can set up your Trimble or Leica base to feed the correction(CMR, RTCM ect.) to a serial port on the base. Keep the port settings in mind for the following part - from here you can use a data modem - RFDesign have some really good ones with good air speeds and output power in the public frequencies. The same on the receiver side, The radio links to the rover serial port and the correction is delivered there for the RTK fix. I've used some of the serial modems for the Topcon robotic TS's data stream. Worked well and small enough for this application. It would be great if the RTK correction could be embedded in the MavLink comms with the vehicle.
@antonie in the video I was sending rtcm via the 3dr radio link that I was also using the the gcs.
@Michael, OK thanks - thats great. I thought you had a second set running the correction. I recall a conversation with one of my RTK GPS suppliers that they ran into latency issues with the length of correction on the CMR format using multiple constellations (GPS+GNSS), hence CMR+ was born. Would this not be an issue embedding the RTCM correction with the rest of the MavLink stream? Too much data carried to remain relevant at 1Hz?
the gps was set to low latency rtk, not time matched, so although latency does play into it, with the base I was using, I had direct access to, so there was no internet induced latency.technically the tlog from that flight would have the encapsulated rtcm in it.
My Reach RTK units (base and rover) just arrived from EMLID. Just $570 for the pair. APM/Pixhawak support is coming soon, they say
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