I can say that I’m getting Fix with RS2 and RTK and have post-processed from a M+ mounted on a UAV at a distance of 1km, getting fixes for all camera events, but I don’t know if this L2 SNR means something bad on the RS2.
Position of the Reach RS2 was on a 2m Mast. Nearest Mobileantenna is > 400m away. There is only a field, a road and Railway tracks nearby.
My RF Equipment was a FrSky Remote Controller (2.4GHz) and a 848Mhz Telemetry Link for the UAV, my Position was more than 5m away from the GNSS Position.
So why is G07 so much worse on L2 Band on the Ground GNSS than on the Airborne Septentrio System?
As Christian has already pointed out, it’s absolutely normal for the L2 SNR to be lower than the L1 SNR.
Andreas, the issue with the post-processing hardly seems to be connected to the difference between SNR values for L1 and L2 frequencies. To help us determine the cause of the issue, would you mind sharing your files from both base and rover so that we can take a closer look? Could you please specify if the software is capable of processing L2C data only or it requires an L2P signal as well?
It may be the case, that L2 SNR is systematically lower than L1 I do not doubt it. However the UAV has significantly better L2 SNR for the chosen Sat than the Base. I’ll send you all the files via PM.
Maybe I’m wrong, but after doing some research I think that it may be related to the receiver/antenna. I have logs from other L2 GPS receivers and can see that L2 SNR values are pretty similar to L1 (50db), while on the RS2 it’s almost never higher than 40, as I described on my previous post.
Maybe it’s a characteristic of the RS2, and I’m not saying it’s necessarily a bad thing because I prefer having L2 than not having it.
I’m having good results in short distances. I don’t know if there can be any issues or disadvantages when doing PPK for longer baselines (more than 20km) with these L2 SNR values comparing with receivers with higher SRN values.
What is the elevation angle of that satellite? I’m thinking that a very low angle satellite might have more interference from ground obstacles than what you’d get on a drone that’s above most objects.
What about satellites with high angles? Any significant difference between Emlid/Septentrio?
According to the log from Andreas’ drone, the L2 quality of its data is not drastically different from the L2 quality of the Reach RS2. I’ll attach the screenshots from both of them so it’s easier to understand.
For example, you can see that SNR for GPS satellites is above 25 only for G30 (it’s around 30) on the drone. Also, for the GLONASS constellation, there are some cycle slips present, especially for R19, R20, and R21.
Reach RS2’s GPS data SNR is mainly above 30 including with higher values for certain satellites (around 40 for G30, around 35 for G07, etc). GLONASS SNR for the L2 is mainly above 35.
However, this slight difference doesn’t prevent us from getting successful post-processing results. I’ve post-processed the logs from Reach RS2 base and Wingtra drone in RTKPost with an almost 96% fix solution. I’ll attach the screenshot.
I assume that the issue Andreas faced with the Wingtra ONE software is due to the specifics requirements of the software. It’d be great to understand what they are.
Andreas, would it be possible to find out whether the software requires L2P data alongside L2C? Reach RS2 records only L2C signal so this might be the reason for the issues with post-processing.
Just wanted to add that it’d be great to test the software ourselves. Would it be possible for you to introduce me to the Customer Service agent at Wingtra who had taken a look at the logs already?
I was referring to RS2, not M2. I say that maybe the antenna/receiver on RS2 has that capability of receving L2 with SNR values up to 40db (or a bit more), while other L2 GPS can receive up to 50db.
At least that’s what I can figure from the logs that I have:
It would be interesting to see RTKPLOT’s “L2” drop-down changed to “L2C”, so we are comparing apples to apples. As Polina mentioned above, Reach doesn’t use L2P signals, which are probably included in the other two graphs and they may have different SNR characteristics or cutoffs.