Consistent lack of L2 Signal from certain satellites

I have been doing some static loggings with the Reach RS2 for the past few months. The sites have a general good view of the sky. Afterword, I download the UBX file to create the rinex observation file for submittal to OPUS. The issue I am seeing is I have only been able to get L1 signal from a few satellites (G16, G21 and G22). Occassionally, after submitting the generated file to OPUS, the file will be rejected (error 9011). I then take out the L1 only satellites and resubmit - which is usually success.

Any thoughts on the reason for L1 only from certain satellites.

https://gssc.esa.int/navipedia/index.php/GPS_Signal_Plan

For L2 your receiver can only track satellites broadcasting the newer L2C signal and not the older L2P signal. There are still a few older sats in service which don’t have L2C. G16, G21, and G22 are examples.

When Ublox designed the chip in your receiver the expectation was that the GPS system would have been completely modernized by 2020 and all sats would have L2C. Since decoding L2P is more problematic they didn’t bother with that. Well modernization is still not complete hence an L2C-only receiver can’t track L2 on a few sats.

This is not an issue if using other constellation dual frequency sats as there are so many, but for older software like OPUS or AUSPOS which are still dual frequency GPS only - missing a few sats hurts a little.

While a completely modernized GPS system is still years off, the good news for OPUS users is an all constellation version is planned to be up and running by the end of the year. If it actually happens OPUS will be much more robust.

8 Likes

Hi @TKrop,

When All frequency is selected, frequencies in the right bottom corner are uninformative and don’t represent the whole picture of tracked signals. You can check the presence of L2 and other signals by selecting them in All frequency setting of the plot. I’ve picked up L2 signal in the random log and here’s what Emlid Studio shows:


Regarding the OPUS, it can reject the log due to the uneven RINEX epochs or time interval different from 30 seconds. We recommend using our OPUS preset for it.

You can send us your raw data log for analyzing to support@emlid.com, I’ll check it for L2 presence and OPUS compatibility.

1 Like