Got a RFQ & part of the submission documents are the latest calibration certificates for the instruments to be used - total stations, level, GPS.
The total stations & levels I have from the last time that I had them repaired. part of the repair apprently was to re-calibrate them.
It is the GPS instruments that I am stuck with. Do you calibrate GPS? I asked a reseller & he told me that they have no set procedure to calibrate a GPS.
How or who does the GPS calibration?
> How or who does the GPS calibration?
I think that Leica Geosystems may be offering this for $1000 in Las Vegas, but I'm not certain.
Actually, I'd think about all you could calibrate on a survey-grade GPS system would be the mechanisms by which the antenna is centered over the ground mark and the antenna heights are determined. If you're mixing antennas from different manufacturers, there is the need to use consistent antenna models, and I suppose you could verify that your software is using them.
A GPS system does not actually measure anything in the conventional sense.
The receiver records signals at timed intervals from satellites to an antenna setup over a site and processing of that information is converted into vectors that when combined make it possible to calculate a position to that site.
The only thing to calibrate or sync would be having an operating GPS system connected to the proper antenna and loaded with the correct firmware.
You may be thinking about obtaining the correct antenna height for your unit.
There is more going on that that, however, that is how I would explain the basics.
0.02
Howdy,
Sounds expensive.
While an errant clock can be a problem, my experience with GPS receivers indicates more problems reside in users and data reduction.
The Canadians also have some GPS calibration baselines. The US NGS also explored this option but did not pursue it. See: http://srd.alberta.ca/LandsForests/DirectorOfSurveys/documents/EdmontonGPSValidationNetworkManual-Mar-1997.pdf
Perhaps the calibration to which they refer is merely the GPS antenna calibration like those done by the US NGS and others. These are for models not individual antennas though that could probably be arranged.
Cheers,
DMM
Not sure if calibrating is the correct term here ... ours is called a test certificate
We have this yearly check routine.
We set 2 receivers side by side and log data for 1 hour, both have the same survey style applied and log data every second.
These files are checked against each other by our dealer, he makes up a 'Test Certifcite', it says that the unit reaches the factory specifications.
Chr.
Take Them To A Calibration Baseline
Set them up, send to OPUS, post process, compare possitions and distances. Keep good notes.
Paul in PA
Take Them To A Calibration Baseline
and attach this...
#stillmakesmelaugh
Do It Your Self - GPS Calibration, Zero Baseline Test & Short Baseline Test
Method 1 - Zero Baseline Test:
If your GPS equipment is the older style separate GPS Receivers & Antennas, set one physical point at your shop, using one external GPS antenna, run the antenna cable to a (2 to 1) GPS signal spliter, the lead cable from the GPS antenna provides the input signal, split the signal output into two separate GPS receivers,(may need to a use DC block on one GPS unit), collect static data files on both GPS receivers,(OPUS style). Download each of the data files from both receivers, Post-Process the Vector/Baseline. The resulting Vector, or Baseline should have a VERY-VERY short distance and an Azimuth.
Method 2 - Short Baseline Test:
Using two Smart Antennas, layout a short fixed distance baseline at your shop, say 5 or 10 meters. Collect static data (OPUS Style)on the short Baseline, download the static files from both GNSS Smart antennas.
Using your own Post-Processing S/w, create a new project, import the two static data files, Post-Process the Vector/Baseline between the two data files, (short Baseline), Compare the Post-Processed Baseline length against the known Baseline length. There should be a very small difference.
AKA the Zero Baseline Test, or the Short Baseline Test.
Bob LeMoine, Hemisphere GNSS B-)
It is worth making up a short bar from a length of 1/4" thick aluminium - drilled with two 5/8" holes about 18" apart.
Mount base station GPS on a tripod with the support rod through one hole. Fix rover GPS to other hole with a suitable 5/8" bolt.
Run static for 20 minutes. The rotate bar through 90 degrees and repeat.
You know exactly what the baseline length should be (as you can measure it with a steel rule), so the processed results will give you a very good indication of any errors which are not due to atmospheric conditions.
We normally get one of our EDM calibrated every couple of years and then use that on our local baseline (which has 8 positions up to 900 metres)to check the rest of the instruments. We run the GPS through at the same time so we get a further comparison.
Be careful about service agent "Calibrations". An EDM can't be calibrated by itself - for the certificate to have meaning the instrument must be calibrated with the prism/holder/mount which is going to be used as the calibrated set with that instrument. Anything else is just a "check".
Take Them To A Calibration Baseline
stealth antenna!! wonder if he noticed all his positions were exactly the same.
Set up on an NGS HARN/HPGN/CBN station and see if you agree with the data sheet.
[sarcasm]The same way to calibrate your plumb bobs - only it takes more time and a bunch more money.[/sarcasm]
"......calibration certificates for the instruments to be used - total stations, level, GPS."
Ther are all sorts of certification templates on line, make your own 🙂
Useless carry-over RFQ specification from a bureaucrat.
There's nothing to calibrate. Nothing to adjust.
Unless you're bored and want to spend time on it to review your data collection procedures, it's a complete waste of time.
> Got a RFQ & part of the submission documents are the latest calibration certificates for the instruments to be used - total stations, level, GPS.
>
> The total stations & levels I have from the last time that I had them repaired. part of the repair apprently was to re-calibrate them.
>
> It is the GPS instruments that I am stuck with. Do you calibrate GPS? I asked a reseller & he told me that they have no set procedure to calibrate a GPS.
>
> How or who does the GPS calibration?
Actually It Is Calibrating The GPS User
There is nothing one can really adjust in a GPS receiver. The point is to prove that you have adjutsed out field operator error and/or post processing person error.
Occupying multiple points on a baseline does multiple checks on your work processes.
Paul in PA
Actually It Is Calibrating The GPS User
Useless carry-over RFQ specification from a bureaucrat.
There's nothing to calibrate. Nothing to adjust.
Unless you're bored and want to spend time on it to review your data collection procedures, it's a complete waste of time.
yes I know, but try to reason it out with those gov't bid committees, going to the dentist for a root canal would be more satisfying:-/
Actually It Is Calibrating The GPS User
Believe it or not there actually is a calibration routine and ISO certification for GPS Receivers. I don't think there is a lot of people out there that do it other than the manufacturers, but it can be done and as far as I know if is pretty expensive.
I believe the routine has something to do with a dual mount with two receivers spaced at a specific distance. The GPS receivers are checked on one side and then moved to the other for verification of both position, timing and center values. I believe the process is done multiple times for comparison and then accuracy can be verified. I've never done one, but I have had several customers that have been required to get this.
Actually It Is Calibrating The GPS User
There is no calibration because there is nothing to adjust.
You can confirm that your field procedures are in accordance with manufacturer recommendations, but that's about it.
Think about it for a minute.
Let's say you run a test and the results don't meet the manufacturer spec. The only course of action is to do the test again or review your field procedures for correctness (or I guess you could toss the receiver and consider it defective). There's nothing you can adjust on the receiver or antenna to improve its accuracy. It's all about operating procedures and operating environment.
> Believe it or not there actually is a calibration routine and ISO certification for GPS Receivers. I don't think there is a lot of people out there that do it other than the manufacturers, but it can be done and as far as I know if is pretty expensive.
>
> I believe the routine has something to do with a dual mount with two receivers spaced at a specific distance. The GPS receivers are checked on one side and then moved to the other for verification of both position, timing and center values. I believe the process is done multiple times for comparison and then accuracy can be verified. I've never done one, but I have had several customers that have been required to get this.
Actually It Is Calibrating The GPS User
I believe there is a phase center adjustment that can be made.
Again, they call and correlate this "verification procedure" a calibration. Whether right nor wrong a certificate that shows test results matching manufacturer specs is what the organization is looking for.
Actually It Is Calibrating The GPS User
Don't take offense, but I don't think anyone on this discussion group is qualified to "adjust" the antenna phase center values provided by the manufacturer. The thought of the average surveyor thinking they can "adjust" these values is (insert your favorite word synonymous with crazy).
NGS publishes phase center values for most GNSS antennas used by surveying receivers.
> I believe there is a phase center adjustment that can be made.
>
> Again, they call and correlate this "verification procedure" a calibration. Whether right nor wrong a certificate that shows test results matching manufacturer specs is what the organization is looking for.
