Strange Issues with GLONASS

We have recently been doing PPK aerial surveys of coastal locations, each survey area was approximately 100 hectares and we set an arbitrary base and around 12 GCPs per site. Our workflow was the standard one we use with three RS2s and a P4R:

Set up base to log GPS, GLONASS and Galileo at 0.5Hz;
After 30 minutes start setting out GCPs and measure each with 3 minute observations;
Fly missions with P4R in PPK mode;
Collect up the GCPs;
Remove base (usually a minimum of four hours logging);
PPK base using local CORS RINEX data in RTKPost;
PPK GCPs using base RINEX data in RTKPost;
PPK P4R using base RINEX data in RedToolbox;
Process photogrammetry.

For every site the base processed perfectly with fix solution and 999.9 AR ratio. The solution was converted to XYZ and pasted in to the base RINEX header, and RTKConv was used to segment the base observations into timespans for the flight missions (this is a limitation of RedToolbox that doesn’t like big RINEX files), without fail all the P4R camera position achieved a fix.

When it came to the GCPs, RTKPost showed a float solution in most cases, however with the exception of one or two the .pos files showed a fix with a very low (~3.5) AR ratio using all three constellations. Looking at the satellite chart there were a few cycle slips but nothing too serious. I played around with various settings with the same results, then tried one in another app which achieved a fix with much higher AR ratio but only used GPS. Back to RTKPost I tried excluding constellations and achieved a fix with 999.9 AR ratio using GPS and Galileo, excluding GLONASS. It seems that the GLONASS satellites were providing erroneous data but I can’t find any information on this, has anyone else experienced this over the last week?

Sorry for the long post but it does provide a background to our workflow which normally works great!

999.9% sure the GLONASS constellation is either having issues or being tweak on. Whether it’s good or bad. We are in Central Texas and cut them out more often than not. We have started introducing Beidou when appropriate but also run primarily GPS and Galileo.

:smiling_face_with_three_hearts: :heart_eyes:Galileo :heart_eyes: :smiling_face_with_three_hearts:

Four atomic clocks, the power and accuracy of averaging.

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Don’t want to go offtopic… but wonder what is to come for all this and Elon Musk’s SPACEX STAR LINK?!

Yeah, everybody with a phone will “all of a sudden” be a surveyor just like how Google made everyone an “instant genius”? : /

; )

EDIT: After some reading, doesn’t appear StarLink would be all that’s it’s cracked up to be for location accuracy.

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Sorry, but Emlid already achieved this, I am a farmer with a RS2, phone and a stick. I can now find my property pins according to the county survey plan relative to NAD83.

I also can plan drainage on my property. Take elevations of the highest hills in my area just for recreation.

Once I master QGIS my fence lines and tree lines will be the best in the county. I will be able to give the next owner of my property a great gift, where and how deep everything is buried.


Sorry… meant with just the phone itself, cm accuracy, no external equipment. It will get there sooner than we know it… and probably already has. ; )

My father ran backhoe for considerable time and was a fan of early survey history. He always made sure on the farm that we did all construction with his prized second hand transit.

Though originally I got into Emlids to make the tractor drive straighter. The RS2 is a fun hobby, for us.

If cellphones could be that accurate it would be cool, but if there is one thing i have learned its not just as easy as carrying the stick.

I have tons of fun within the bounds already laid out by professional surveyors. I treat the legal survey markers with great importance. One surveyor is worth twelve lawyers.

No, Star Link doesn’t have anything to do with the L5 deployment. Those will be different satellites. Some of which are already in orbit just not accessible. Star Link will surely provide some terrestrial guidance of some sort though similar to AGPS.

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A bubble level on screen, lasers and voice-activate shot taking.

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