RS2 rover says that base has fewer satellites

I have noticed this difference as well.

I assumed that base saw 20 sats, no corrections = base 20 sats

But the rover and base may not see the exact same satellites so some corrections are not used.

Then if rover saw 18 sats + 15 usable (same sat) corrections = rover 33 sats

Thats how i assume it works, very interested in this answer as well.

Hi @PotatoFarmer,

It’d be nice if you may share screencast showing it and/or the following files:

  • raw data logs from the base and rover
  • solution file from the rover
  • base correction file from the rover
  • simple system reports from both devices

Ok I have done some testing

Outside open air, barely any differences.

I see wildly different numbers like you describe with the two antennas side by side, sitting in a window, or outside on my deck.

But what i have noticed is if the antennas are way too close one will block or shade the other, also if antennas not properly levelled with each other I get also get messed up numbers.

Hope this helps.

Hi @tatiana.andreeva and @PotatoFarmer, I also just did some testing today. I’m at a different site and getting better results than before (but still strange). Now when the base says it has 35 satellites, the rover says the base has ~30 satellites (and it says the rover itself has 35). I still don’t understand why there is any differene, but at least this is a smaller discrepancy. Attached is the screenshot showing the base has all the constellations enabled:

And a second showing the rover has 34 satellites while the base has 29. They are sitting on the same surface about 50 cm apart with the same sky view.

Unlike @PotatoFarmer, I do not see a difference if the units are leveled slightly differently.

I could send the device logs if that would be helpful–let me know which ones you would need.

Hi @PotatoFarmer, @djyoung,

I’m afraid it’s quite hard to come up with any conclusion before we can look into the following files:

There might be a lot of the reasons for such behavior. However, to find out what is the particular one in your cases, we need to check the data.

Sorry been busy,

The only time for me the numbers look goofy is extreme short baseline, with antennas in a window.

Outside there is no issue for me.

OK thanks @tatiana.andreeva. Here are those files. Let me know if you can solve this mystery!

logs.zip (1.8 MB)

Thanks,
Derek

Hi Derek,

Thanks for sharing the files! We’ll check them and get back with the news.

Hi Derek,

Thanks for your patience!

I’ve looked through the data you provided. You can see the satellite signals on the screenshots of the base observational data and the base correction log from the rover. On the base correction log, there are 25 satellites. The base sees 32 satellites.

The base doesn’t transmit the data on 7 satellites (G03, G20, G23, G25, R12, R26, E27) as they signal is heavily interrupted during the survey and the SNR is less than 25 which is not suitable for transmittance.

Have you encountered any issues with the incorrect number of the base’s satellites shown in the Status tab during this survey?

Also, you can see on the base correction log there are some interruptions of the signal every 25-30 seconds. Such interruptions might be caused by the setup when the LoRa radio signal gets blocked. Could you please attach the photo of the hardware setup so that we could check what affects the signal?

Hi Liudmila – thanks for the reply, and sorry for my delayed response. Fiedwork was keeping me too busy to respond.

Here is a photo of the rover and base in a typical environment. In this environment, the rover had 37 satellites but was receiving base corrections for only 32, even though the base had 37 satellites.

If it would help, I can send the logs and ReachView screenshots I took from the base and rover when they were in this position.

I’m not sure exactly clear what you mean. I think the answer is yes: on the status tab for the base, the base says it sees 37 satellites, while on the status table for the rover, the rover says the base is transmitting only 32 satellites.

Again, happy to send logs and screenshots associated with this specific photo if that would help.

Thanks for your help!

Is this a curiosity question or an issue? Having 30+ satellites to work with in a solution should be no problem.

This was actually a delayed response to Liudmila’s question and request for a photo. I believe it is more of an issue than a curiosity question. The rover always gets corrections for significantly fewer satellites than the base sees no matter what environment I’m in; in more difficult environments, this can mean the number of satellites with corrections drops below 20, even when the rover and base both see far more satellites.

7 posts were split to a new topic: Firmware versions on Reach devices

The reason why it would have less sats at the rover can be a few things , low snr of that sattilite , Is not seeing the exact same sat and in Rtk settings not have the same consultations selected. Emlid is a great product.

I think the post says the rover says base has fewer sats than what is reported at the base unit. maybe the base unit says it sees 15 sats but when you check from the rover maybe it says 10 sats. from a user holding the rover, if I see for example that the base is seeing only 10 sats when in reality it is seeing 15 sats, I might go back to the base and change its location only to find out that it actually sees 15 sats. waste of time for surveyors in the field.
if the rover says that it is only using 10 sats from a total of 15 sats seen by the base then that is another matter.

Your first interpretation is correct. That is my situation. It’s that the base is not transmitting corrections for all the sats that it sees…or at least that the rover is not receiving all the corrections. This happens even if the units are right next to each other in a flat landscape, like in my photo. I’m trying to understand if this is expected behavior or not.

If you change the snr mask or the elevation mask, does the number base sats change? That should be a good indication of what is going on.

Hi Derek,

Thanks for the info!

The quantity of the satellite signals that the base receives and sends to the rover can be different. The base doesn’t transmit the correction messages from the satellites that have low SNR. The data quality of such signals won’t be enough to calculate the Fix solution as they are very noisy.

Your base has tracked overall 37 satellites but transmitted only 32 signals as the rover showed it in the Status tab. It means that 5 satellite signals were of poor quality. They won’t be transmitted so that it won’t affect the solution calculations. It’s the method of how the receiver’s algorithms work, there’s no issue in the device.

It’d be great to check the logs from the last survey. However, as I’ve mentioned in my previous post, the data from your previous survey showed that the base didn’t transmit heavily interrupted signals with the SNR is less than 25.

2 Likes

Thank you very much Liudmila and others. This makes a lot of sense. I’ll stop worrying about the difference in the satellite numbers. I am very pleased with Emlid’s product quality and support.

4 Likes

This topic was automatically closed 100 days after the last reply. New replies are no longer allowed.