Post-processing Reach M2 files with OPUS

New here on the community, long time land surveyor for 40+ years; been using GPS since late 80’s.
Just bought me a M2 and plan on using as a cheap base receiver to shorten observation lines with other well-known receiver brands. I’ve found out in my use of GPS/GNSS receivers, that it pays to have short baselines. Also OPUS is awful picky in their observation data that’s submitted. In the case of “fewer than 3 usable reference stations remain. Aborting” messgae, it’s usually bad data at the CORS sites that OPUS is using for processing. I would suggest to select manually the reference stations in the “OPTIONS” menu. Always, try and select the closest stations. And always have sufficient observation time on station for submitting, i.e. 1 hour minimum with clear sky view.
I submitted my M2 first data (1.5 hours) to OPUS and got the same message, even after trying other stations, 4 or 5 times of submitting. I ended up post-processing myself using a local station
network with baselines <5 miles (8 km) and finally got excellent results (2 cm horizontal/3cm vertical). I very seldom use OPUS unless it’s necessary or I’m needing data. Down through the years, we’ve established a local network of terrestrial marks usually within 5-10 miles in our area tied to the NSRS (National Spatial Reference System). I’ll usually use one of these as a base station.


Hi Bryan, I am also a land surveyor thinking of using the M2 as a base station if possible and an RS2 as a rover. One question I have is what method to use to center the M2 over a known point? Any other advice you can give me concerning this setup would be greatly appreciated. Thanks. James

Obvious for a RLS, but it’s antenna, not the M2 itself that needs to centered.
That makes the exercise much easier, as most antennas have their threading centered as well.

James, get a survey type antenna, the one you can install on tribrach or pole,
plus the M+ TNC antenna adapter (see in Emlid store).


I hadn’t really looked that hard for an antenna to replace the helical M2 antenna. For the first observation on my new M2, I simply taped the antenna to the top of the bi-pod mount and measured the ARP and also entered the phase L1 and L2 distances when creating a new antenna template in my PP software. For the price, I don’t think you can beat the M2 as a basic reference receiver, at least for me. We have JAVAD gear here and it’s a wondrous piece of equipment, but I’ve always wanted just a no-frills base receiver for short baselines (<1-2 miles). From my preliminary first use, I’m pretty pleased for the performance. I’m planning on rigging an antenna mount this weekend using some pvc pipe and caps (approx 2.5" dia and about 3" tall). I’ve envisioned in my brain that this would also enclose the receiver itself from the elements. I’ll post pics once it’s finished. I just can’t see spending $1K or more for an antenna for this receiver.

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Here’s the first version of the mount. Center piece is not long enough to enclose the

receiver. Receiver and battery in blue bag


The antenna I shown is around 90 € in Spain.

I’ll have to check on the various antennas. Tallysman makes the M2 antenna. They speak highly of the product, I think this is it

I’ve only used the M2 twice and I’m pleased with the product. It wasn’t intended as a static receiver as the RS2. If Emlid would design a survey mount for the antenna, I think this would open another door for sales, just as adding more survey friendly features to their app would.

Interesting thread. I am also a surveyor and looking for solutions to integrate the M2 to Phantom 4 Advanced.
But this option to make it base receiver is very interesting. I have a question though.
Is it possible to broadcast corrections with the LoRa radio and then connect a rover with older type PDL UHF modem?

You can do Emlid LoRa to Emlid LoRa or you can do 3rd party radio to 3rd party radio, but not mix them. To connect a third-party radio to the M2 you can make use of the UART pins (TX/RX/GND). Otherwise is is more simple to just use an Emlid Reach RS2 base and its built-in LoRa.

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