We have a ToR for a 40Ha topo of flat urban/rural land, and under "Primary Survey Control" it says:
"Primary Survey Control point Dual reference pillars shall be established once in every 0.5km using GNSS Static method having valid calibration certificate".
There may be other anomalies in that spec, but in the first instance, is a "calibration certificate" sensical in this context??ÿ
I think this was covered some years back. There's nothing to adjust on a production GNSS receiver, so there's not really a calibration certificate per se.
I guess you could get a certificate from your dealer stating that it meets factory standards (i.e. hasn't been modified), but it's not like you can tweak your APC.
If it does meet factory standards, and your antenna model has ANTEX absolute calibration values, you should be good to go.
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(If anyone actually does have a calibration certificate, I would love to see it, and as well as find out what exactly the user would be "adjusting" during the calibration process.)
I would say the calibration certificate is a hold over from total station requirements.?ÿ I have had numerous project at require the TS has a recent calibration report from the manufacture/dealer.
What is a TOR survey?
ToR = Terms of Reference.
I agree that the "calibration certificate" is likely to be a hold over from optical/mechanical instruments. Trouble is, down this way, now that someone's written it, it's difficult to get it out.
Can you give them a report of a static session done with that equipment on an officially known point for comparison?
Yes, that would be a good idea of something to offer.
They want you to set concrete pillars for control on a topo??ÿ I set (okay I have the contractor build) pillars for structural monitoring but it seems WAY overkill for a topo.?ÿ Let alone every 500 m.
There is this from Canada: https://open.alberta.ca/dataset/10fd0369-8de5-4e9e-8d98-b17eb8abf72e/resource/6fd2eb0b-41ea-4a14-9e87-c49a45e526a8/download/edmontongpsvalidationmanual-mar1997.pdf
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I think that part of the ToR has come from a roading survey project, probably with the intent to use total station. It's a real mix and un-match.
The phrase "serve as a physical standard for evaluating GPS equipment, software, and positioning methodologies" makes me wonder whether it is intended for evaluating models of receivers as a class, or individual receivers.
Like others were saying, it's a pretty straightforward test to run a static session on a validation site, post-process and demonstrate that your receiver is working as it should. But that's not really "calibration", and I don't know how you as the professional could create a certificate to that effect.
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On a related note, I would be interested to hear of any stories people have of a particular GNSS receiver having a "bad calibration" or otherwise returning results with clear systematic bias when compared to other receivers of the same model. Personally, I have never experienced it or heard of it happening, but I haven't been doing this as long as a lot of other folks.
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I agree that the document and excerpt I posted would not provide calibration information.?ÿThe linked document refers to the sites being a ??GPS Validation Network.??ÿ
The intent, as I understand it, is to allow users to validate their individual equipment against a well-determined network of points. The design includes pillars, forced-centering, sites clear of obstructions and varying ranges that eliminate some error sources.
As I see it, the network is useful to establish that a users equipment and processing software can replicate to a high-level of accuracy the coordinates of the points in a well-determined network.
In the early days of commercial GPS, the FGCS did do equipment testing at a network of points. Some of the old reports should be available from the NGS site.
I have not kept track of the Canadian efforts but recollected them when reading this thread.
The intent, as I understand it, is to allow users to validate their individual equipment against a well-determined network of points. The design includes pillars, forced-centering, sites clear of obstructions and varying ranges that eliminate some error sources.
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If I understand GPS post-processing concepts, you can only get the same coordinates if you observed the same number of satellites? The deviation in RMS will only diminish once you get past a certain threshold in hours of observation which is around 6 hours (?) I believe. If you observe for only 1 hour or less, you will be getting statistical deviations from the published coordinates.
I agree that it's hard to imagine how calibration certificates could be meaningful for GNSS receivers, but if any manufacturer were to provide them it would be Leica. They provide calibration certificates even for the inexpensive (by Leica standards) Disto handheld rangefinders. Leica GNSS users: Have you ever seen one?
