Maintain FIX during movement with M+

I have configured 2 M+, one base and the other rover. The correction is send through LoRa.
I can achieve a FIX status quite rapidly when both M+ are static but when I move the rover I obtain a FLOAT status. I have configured a max acceleration of 5m horizontally and none vertically.
Both are configured with 5hz rate.

Is it normal or should I check my configuration ?

Hi @Tomlogan,

That doesn’t sound like normal behavior for Reach devices. I’d like to investigate why it may happen. Would you mind sharing some data so I may look into them?

First of all, I need the following data from the devices recorded during your test:

  • UBX raw data from both M+
  • position data from M+ rover
  • base correction data from M+ rover

All of them can be downloaded in the Logging tab.

It’s also would be nice to know:

  • What’s the firmware version installed on the device?
  • What’re the RTK Settings on both the base and the rover?
  • Which RTCM3 messages you have chosen in the Base mode of M+ base device?
  1. Latest firmware 2.2.23
  2. I’m using on the base single and on the rover float, I will add a ntrip server on the base
  3. RTCM3 as mention here

I will provide fresh logs tomorrow, should I reconfigure it before ?

Hi @Tomlogan,

I believe you can just share the data from your recent test with the devices.

Hi @tatiana.andreeva,
This afternoon, I got a quite stable FIX but not for long when I move the rover.
On the base, I didn’t install for now a NTRIP server because it would require an WIFI hotspot. (5.5 MB) (117.1 KB) (240.3 KB) (613.7 KB)

Hi @Tomlogan,

Thanks for the data! We’ll analyze them and get back.

Hi @Tomlogan,

Do I understand correctly that you’ve configured to transmit the following RTCM3 messages?

  • 1002 GPS L1 observations
  • 1006 ARP station coordinate


It’d be great if you could just generate the Full System Reports on both units and send them to me in PM. The information in the reports will help us see the settings as well as determine the cause of the issue.

HI @polina.buriak,
Yes I configure for GPS and ARP, I may have forgot GLONASS, is it the cause of the instability ?
I will send you the system report

Hi @Tomlogan,

The information about enabled RTCM3 messages will help me check if there’s anything missing in the data received on the rover. After it’ll be easier to understand what could go amiss.

Looking forward to receiving the Full System Reports.

Hi @Tomlogan,

Thanks for sharing the Full System reports!

I’ll delete your message as the report may contain sensitive information. We’ll look into it and I’ll get back to you with news.

Regarding your questions, the rover position is relative to the base position. It means that if you establish the base’s coordinates with the Average Single, it’s absolute accuracy is meter-level. So is the absolute rover’s.

If you require absolute centimeter-accuracy on the rover, you need to know the base coordinates with the centimeter-level accuracy as well. For that, as you have mentioned, you can use the NTRIP corrections.

Hi @polina.buriak,
Hope you are doing well with this exceptional circumstance.
Any news about the system reports ?

Hi @Tomlogan,

Thank you, hope you’re well too!

Currently, we’re looking into the issue with the fix solution. I’ll inform you once there’s any update on it.

Hi @Tomlogan,

We’ve just released the v2.22.4 firmware version. This update contains an important fix that should improve the solution in RTK.

I’d ask you to update your receivers to this latest stable release and check how it works for you. Please keep us posted on the results.

Hi @polina.buriak,
I got good results with the new firmware, got a FIX with my rudimentary setup.
It seems more stable than before. I can’t test it on the final setup (on a USV) but I think it will be OK.

IMG_20200424_162536_s IMG_20200424_162527_s

Open sky with no obstacles in a field

Here are the logs (2.5 MB) (105.5 KB) (205.4 KB) (238.6 KB) (876.3 KB) (275.0 KB)

Does it need improvements on the rover and the base ?

Hi @Tomlogan,

Thanks for the test! It seems like the latest update is working well for you.

However, I can see that you use GPS and GLONASS only. It means that both base and rover simultaneously see only 5 satellites with SNR around 45 (G18, G21, G26, G31, R09). I’ll attach the screenshots of the logs below.

This is the rover log:

This is the base log:

This might cause some difficulties for the rover to obtain the fix. So I’d recommend enabling more satellite systems for your tests so that the rover can use more data for the calculations. This will help increase the stability of the Fix solution. Our default recommendation is all satellite systems (GPS + GLONASS + Galileo + SBAS + QZSS) enabled at 1 Hz for the base and at 5 Hz for the rover.

It’d be great to see your results with the final setup and on the moving rover!

Hi @polina.buriak
We have order a Reach RS+ as base, hope it will more practical to “set and forget”
I will try again with your configuration.

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Elevating the base will also help quite a bit. I know it is hard on ground based drone, but it can have a huge impact.

Sure that’s why we order a RS+ with a tall tripod :slight_smile:

Sorry, meant both units… so also your rover, most of the time, especially the rover, as it is usually the one facing difficult conditions.