Emlid GNSS positioning not retaining FIX

Hello, we are having problems reaching a steady fix between our stationary base (RS+) and the roamer (M2) which is placed onboard a robot.

In terms of the base station, we do not have problems with the base receiving an RTK/RTS FIX. We have trialed both stationary and kinematic settings and observed no difference. The problems seems to be the roamer itself or communication between the base and the roamer. The roamer receives connections via LoRa at 928Mhz. We test in large open spaces so interference from trees and building should have no effect. People may walk past but not sure that should change anything. The antenna is elevated above the robot, the roamer is away from onboard electronics and we see between 28-30+ satellites at all times. Both systems are also up to date.

The following are the cases we might get:

  1. The signal switches between FIX and FLOAT every few seconds continuously. Only way we have found to overcome this is to turn the robot off and back on.
  2. The signal remains in FLOAT for over 20 minutes. Might converge after this time but generally we don’t wait for this long and restart the robot.
  3. Works perfectly and converges nearly immediately or up to 5 minutes.
    The problem cases (1 and 2) occur more than 50% of the time and turning the robot off and on again we might experience a different case even though nothing has changed.

We have tried different interference testing:

  • The computer onboard the robot hosts a website at 2.4GHz on our phones so we thought - this could potentially be interfering. We tried different phone positions but this had no affect.
  • Standing right next to the base vs. keeping clear to determine if interference from us.
  • Changing the base to static. No change in getting a FIX

Are there any other suggestions to achieve a more consistent FIX?

Thank you

Hi @Katherine_Ryan,

Apologies for the radio silence here.

RS+ is a single-band receiver, while M2 is a multi-frequency receiver. You can’t use RS+ as the base for your M2 because it sends only L1 corrections, which is probably why you can’t get a stable FIX with this setup.

You can use the M2 as the base and the RS+ as the rover. However, this setup doesn’t offer the advantages of working with multi-band receivers. Further, you would need to consider how to set up the M2 as the base, which can be tricky.

Hello @ruth.bongon,
I just want to add to my original post that it is the M2/M+ LoRa radio as the roamer - not just the M2.

This makes a lot of sense thank you! What emlid setup would you suggest so we can take advantage of the multi frequencies and faster fix? We are open to other emlid devices.

Thank you

Hi @kathrine.wiki20,

Apologies for the delay.

If you have another M2, I suggest using one of them as the base and the other M2 and M+ as the rover.

If you’d like to have another device, will it be set up in the same way? Will you attach this device to a robot?