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@norman-oklahoma
the task is static collection. RTK applications is real-time. The point I made was collecting at or below 10 does not effect the data.
I understand, understood, and agree. But I gather that the OPs prior experience is all with RTK. So I’m giving him background. Not disagreeing with you.
@norman-oklahoma
Ive seen too often the ‘newbie know it all’ freak when I set collection to 5 degree, insisting it must be 15!! So when he asked should he be changing the mask mid-collection I had a bad flashback.
The one nice thing about setting the collection mask to the maximum (smallest horizon angle) post processing mask it the satellite count depicted on the receiver will reflect that seen in post processing. Not that big of a deal in the days of multi constellation, but OPUS is still GPS only so it does help.
BTW, https://kb.unavco.org/kb/assets/660/UNAVCO_Campaign_GPS_GNSS_Handbook.pdf is a nice reference for new and experienced GNSS operators.
I plead guilty to muddling my post.
I blew today’s session because I forgot to orientate the receiver to the north. I logged the session both internally to the receiver and externally to the FC-5000. I parked the Jeep over one hundred feet from the receiver; I’ve heard a running vehicle causes interference, and I do need to run the A/C. Why is the default antennae mask -90?ø? The software is Topcon MAGNET Field.
MHI have always been a fan of check lists and the like. I copy below an NGS Observation Log. It may not be the most recent or may have been superseded. It is quite comprehensive and includes a mini-checklist covering your issue. BTW, orientation is to North not magnetic north. Correct the orientation to account for the declination at the site.
A source for magnetic declination is here: https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml#declination
How to adjust a inexpensive Suunto compass is shown here: https://www.rei.com/learn/expert-advice/compass-declination.html
HTH,
DMM
What does NGS do with the weather data, if anything?
.I haven’t read the entire thread but I would suggest looking on the NGS site to find which Bench Marks locally are included. Try and occupy bench marks that have not already been included, are first order, are still good (haven’t been disturbed) and can be occupied with GPS. That may narrow down the possibilities to just a few local ones. The Bench Marks in my county that fit that description are few, many are in RR right-of-ways, bridge abutments or are vertical so they can’t be occupied. Also some have been moved or disturbed during construction at least a quick tie between two is a good idea. Chose the point wisely.
For instance I’m near an NGS point doing some boundary work, it’s a first order horizontal point I maybe could occupy and submit but the vertical on it is not a valid number so there is little to no value including it.
Orienting the receiver to the north is an outdated practice if you have anywhere close to a modern receiver for which there is an absolute antenna calibration.
While there is such a thing as the NRP (north reference point), there are several receivers that have no such point identified on the ANTCAL sheets. Practically speaking, there will be little difference between a position derived with the NRP pointing north, or not. The difference between the two will almost certainly be below the error noise when comparing two OPUS solutions.
Is it best practices? Yes. Does it “blow your session”? Absolutely not. Particularly when you consider how many large-scale GNSS networks utilize many different receiver makes and models – I can remember several networks I ran with 8 to 12 receivers of at least four or five different models.
As for the antenna mask, I have no idea. That should be something set up by the controller survey style or in the receiver itself.
That mask value shouldn’t make a difference when you post-process, which has already been covered upthread.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil PostmanI wouldn’t throw the baby out with the bath water for not orienting north if your receiver is fairly modern. I wouldn’t know how to orient ours. There’s no mark for it like there was on legacy receivers. Our equipment manuals haven’t referred to north orientation for at least 10 years but they are very detailed about other aspects of setting up. The NGS guys are probably cringing. If you’re worried about it process both ways and compare.
orienting the antenna N is to match the NGS?? antenna calibration. The electronic phase center is not the same as the physical center of the antenna chassis. And the electronic phase center is subject to the direction and elevation of the signal path of ea SV
In the much older helical coil antenna this was a bigger issue. With micro strip antenna these offsets are greatly reduced, in most cases negligible. In subsidence or very hi accuracy work, you mind the details even if small.
Orienting N is to replicate orientation used for the precise antenna calibration procedure.
The first GPS receiver I ever had contact with (c.1997) had an orientation mark on it. There was some talk of orienting that thing to north, but on later advice from the manufacturer (Leica, in that case) that was dropped. No receiver I’ve used since that one (mostly Trimbles, but some Leicas and Topcons) has had any such mark, and no one has ever mentioned any need to orient it in any particular direction. Anyway, this GPS on Benchmarks thing is for elevation, and antenna orientation could have no possible effect on the vertical.
I suspect -90 is functionally zero. And zero elev mask is harmless to data collected. The post processing can invoke higher masks than collected.
The receiver will not record data below the mask that is set in the receiver. So erring to lower (zero) returns data that is of no ill consequence.
And not all antennae are of equal quality. Geodetic ground plane antennae versus small compact antennae for use on a stacking pole. A Good antenna used to cost $5K. Like CORS and UNAVCO spec antennae.
FYI, OPUS does not require a RINEX upload. Whenever you do upload a non-RINEX file to OPUS, the first step within the OPUS “engine” is that it converts your raw file to RINEX using TEQC.
For example, Topcon .tps files will upload directly to OPUS. I think the the Trimble .dat files will also direct upload to OPUS, but I don’t have one on-hand to double-check right now. I can say that it will not accept Trimble .T02 or the new .T04 files, users need to convert to RINEX, and I highly recommend using ConvertToRINEX to do that. For that matter, I recommend to always use the manufacturer’s provided software to convert their raw files.
The thinking at NGS has always been to gather as much information as possible in order to not only process the observations but also to test the results of different approaches. For example, the weather data (and more obscurely the weather codes) can be used instead of standard values in PAGE-NT vector reduction. Not that it should.
While NGS observers were equipped with accurate barometers and sling psychrometers and were trained in their use, I have seen data from other users indicating they did not have a clue. In other words, the quality of the observations was often suspect. Surface meteorological observations even when well done do not represent the conditions effecting the signal as it passes through the troposphere. Of course there are water-vapor radiometers. See:
BTW, I came across this old copy of the PAGE-NT manual: http://geodesyattamucc.pbworks.com/w/file/fetch/115417693/PNT6MAN.PDF
Anymore, the “met data” (met = meterological) is primarily used to diagnose/troubleshoot any issues encountered during processing and adjustment. More important than just logging temps or pressure during GNSS collection is to note severe or rapid changes during data logging/collection.
Absent a North Reference mark you kept the antenna connect point to the South. It was not as important to have an exact North azimuth as to generally be consistent in how you set up. The more consistent you are the less errors you create for yourself.
Paul in PA
- Posted by: @paul-in-pa
Absent a North Reference mark you kept the antenna connect point to the South. It was not as important to have an exact North azimuth as to generally be consistent in how you set up. The more consistent you are the less errors you create for yourself.
Consistency is good. It would definitely help to be consistent within a project. However, for NGS submissions it needs to be right.
The connector orientation probably depends on the manufacturer and perhaps the model. My Trimble antennas have a north mark and the connector is then northeast.
. As indicated elsewhere in this thread, there is a big difference in the types of surveys users perform. For the most precise surveys the absolute antenna calibrations are used. I consider orienting the antenna to part of “best practices.”
The impetus for the first antenna calibrations was to account for the mixing of different antenna models on projects. Large height errors result from the failure to account for the different ways antennas capture the signal. See: https://geodesy.noaa.gov/ANTCAL/FAQ.xhtml#faq11 for more information.
The first calibrations were done in a relative sense by the US NGS. They tabulated elevation-dependent effects. Subsequently technology advanced to allow absolute antenna calibrations. These calibrations tabulate the impact of both horizontal orientation and elevation angle.
I show an extract from the absolute calibration file for the AOA D/M TA NGS NONE (i.e. no radome) antenna. Note that the first column of the table is the azimuth, other column values are vertical angle in five-degree intervals and rows are the azimuth.
Note that the first row of the table is for NO AZI. In other words the antenna was not oriented to north. Scanning through the values shows differences as a function of azimuth and elevation.
I have no current experience with GNSS equipment. I am surprised at comments that there is no way to orient the antenna.
T
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