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.

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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

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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.

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

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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

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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.

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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?

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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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Thanks for the reply.
Is it possible M2 to work as Base Ntrip Server and send corrections to a Caster?
I am thinking if I could integrate the antenna to my car and have the M2 safe inside the car instead of tripods over benchmarks etc.
The ideal workflow is to calculate the position of the base anywhere with RTK by using COORS and then switch to base by sending corrections to a Ntrip Caster.
Is that possible?

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Hi @vgo195,

You can try this workaround. Placing an antenna onto the car roof should be fine.

I would highlight a couple of extra points. To make the whole setup work, you will need an external power source to power it up. Also, you’ll need to supply Reach M2 units with a couple of LoRa antennas if you want to work in RTK mode. To get NTRIP corrections, you can connect Reach M2 to the CORS via mobile hotspot with Internet access.

I hope that helps.

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Thanks,
I have ordered the M2 kit https://store.emlid.com/product/reachm2-with-gnss-antenna/
and will test it as soon as i get it.

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Sounds feasible, but not the step when you want to leave the antenna inside the car. I think you need to leave that antenna over a fixed point while you are working with your rover. This is a friendly observation.

I ordered it today plus the Lora antenna radio.

I don’t mean to leave the antenna inside the car. I mean to fix it somewhere in the rooftop an have the M2 inside the car.
Of course the rooftop of a car if a reflective surface that helps multipath but I have test this with a standard survey grade receiver and worked without problems. With M2’s antenna I have to check it.

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I was thinking on the multipath effect. :+1:

Hi,
Yesterday, I received the m2 + Lora Radio. Today I tested using the m2 as a base and the r2 as a rover.

The rover got the fixed solution in 2-5 seconds.

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Me too got my M2 yesterday!
I did a small test and it did work as is should.
I encountered some problems though.

  1. I did connect to my COORS with NTRIP but for some reason it does not show receiving the base satellites. The problem is with the COORS not the M2 because in the past I was playing with rtkgps+ app and had the same situation with this COORS. It must be something with their decoding.
  2. As far as I could tell there is no option to connect the M2 to an android hotspot if you have one phone and the same time configure M2 with reachview. Right? One has to have a separate phone acting as a hotspot and another phone or (tablet or pc) connected to the same hotspot as M2 in order to access it via reachview. Correct?
  3. I don’t understand if it is possible to receive corrections from a caster and at the same time to broadcast corrections to another caster. It seems that it works that way.
    I will test the unit further to check it but for now it seems very promising…!
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For topic 1 I did not have any issues, I tested the M2 using UNAVCO (P473), connected to my house internet via WiFi.

For topic 2, Is correct, I found the same problem. I will try using a mobile hotspot provided by a cell phone company. Or maybe a 2nd cellphone?

Yesterday, I tested in a real world scenarios the M2 as a base and the RS2 as a rover, using the LoRa radios. The only minor issue I found is when I did some staking and begin moving to the point the rover has some 3-4 seconds delays until it shows the real position. I’ll do more tests for this.

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