NTRIP correction useless near house, Reach M+ base station better near house?

I have a Reach M+ on a ground based robot. I am using NTRIP correction input from CRTN base station about 5km away. When robot is far from house I get good results. Very stable within 5cm. Within 10 meters of the house performance drops and within 5 meters the readings can jump 20 meters per reading. I understand that the house is blocking line of sight to some satellites. Robot only approaches house from one side.

My question is this: If I had a 2nd Reach M+ acting as a base station placed near the house where the same satellites are blocked from the base as would be blocked from the rover when robot approaches house, would I get better behavior from the rover?

Or if there is another way to help improve performance like masking the satellites that have a house-shadow, please feel free to offer alternate ideas.

Thank you in advance for your help.

It not only blocks some signals, it also introduces multipath-issues, so basically reflecting the signal from the visible sats off the wall and back into the receiver, causing “confusion” for the receiver.

Yes, as the baseline gets much shorter. However, the issue won’t disappear, especially as the M+ is L1 only.
If you were to use 2 x RS2 instead you will likely see a much bigger improvement, however, also a different budget.

You’ll seriously reduce / clip the number of satellites and not generally ideal, but you could “try” increasing the “elevation mask angle” to filter out the satellites between rover and house. I.e. from 15 deg to something much narrower like 45 deg. Again, just to see if it helps your situation as ideally you want a wide elevation mask with clear sky view without obstructions, i.e 15 to 10 deg. (15 deg typ. best to filter out ionosphere, distant trees, buildings etc)

Try @wizprod suggestion sat predictor here with basic obstructions:

Maybe look into a robotic total station with a prism $$$ for guidance of your rover robot for higher update rate without dropping out typically associated with gnss?

Thanks wizprod. This is a hobby thing so no RS2 for me. Maybe I’ll try a 2nd M+.

Thanks for suggestion. I’ll test it this weekend. Reach M+ allows adjustment up to 30 degrees.

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Yes, you are correct.

Just remember that doing it this way, also excludes otherwise usable sats from the opposite side of the house, which in turn also lowers your PDOP.


Hi @billy,

Can you see the fix status changes to float at this point?
Are satellite bars starting to be red/orange?

It seems like an environmental conditions issue, I can assume that the second M+ will not help.
As M+ is an L1 device only, it might be challenging for the device to work in such conditions with blocked sky view.
However, you can try to play with Elevation and SNR masks settings as @timd1971 advice.

Let us know about the test results :slightly_smiling_face:

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