It was recently discovered that all of the northern California CRTN mountpoints have been casting incorrect base positions. The problem was fixed today (reportedly for all NorCal stations, I only checked UCD1), but the problem began sometime between January 14 and February 12. If you've relied on any CRTN positions recorded between January 14 and today (March 25), you may want to review them to determine if remedial action is necessary.
Does this effect all gps, or just some brands? And, does it only affect Calif. Or more?
And, only Real Time Networks?
I guess CRTN stands for California Real Time Network?
I don't use RTN'S. Some of us who are non initiate, are overhearing, and trying to get a basic understanding.
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Nate
You are correct Nate. It will only impact you if you were using the CRTN to establish your rover coordinates. You wouldn't want to be publishing values on a Record of Survey that were substantially messed up or have a long duration project that has changing base values. That could be a mess. This warrants surveyors to make checks prior to accepting values that come out of the black box.
This went out from CRTN this afternoon:
Alert (3/26/2019): It was discovered that the northern California CRTN server (132.239.152.175) was transmitting incorrect coordinates in the RTCM3 messages. This started on January 16th when we moved the server to another workstation. The problem was resolved in the late afternoon of March 26th. Anyone who relied on the CRTN coordinates over this time period will need to revisit their rover coordinates. Please contact us if you believe your surveys may have been affected by the erroneous coordinates. Note that the southern California server was not affected. Thanks to Jim Frame and Art Andrew for discovering the problem. We??re sorry for the inconvenience.
Ooopsie! I always try to verify my RTN recorded CORS positions with the published datasheets. Some networks make this easier than others. If I find slight discrepancies (not uncommon), I will update the base (CORS) positions and make the slight shifts to the rover (unknown) positions.
This all seems like good practice no matter the source of the RTN positions. I can't tell you how many issues I find with wrong antennas, wrong positions, data not turned on (forgot to configure for GLONASS or L2, etc.) each year. It is actually more than you would think, data is only as good as the humans programming the box to do what they tell it. I politely and professionally point out what I find to the operator, they fix it and I go on my way, we all human.
I work across many networks in many states each year for both RTN and post processed static, so I suspect I see a bit bigger cross section than most...
SHG
Jim, you are an asset to the profession.
Nate
Way back in 2001 when I first started using RTK, a wise and experienced surveyor gave me this advice, "Never walk past a point you've shot before [with RTK]." That advice also applies to RTNs.
Also, no surprise that Jim and Shelby are well ahead of the curve!