Ah...
Well, measuring for measurements sake is one thing.
Otherwise, you might want to take up a vice to help ease the pain of practicality.
Best of luck!
It's on top of a double story concrete building, looks reasonably solid to me, more solid than a tripod (which moves around with temperature throughout the day), I don't know much about their configuration, how it's supported etc, I only know the antenna type for post processing. Their data is broken into 24 hour periods, submitted to AUSPOS.
AUSPOS reports give a vertical height interval of 8mm @ 95% confidence on average for each 24 hour period.
20 days of GPS data (averaged): height range: 22mm, rmsd 3mm. These people are registered surveyors, they've given me no reason to doubt their work.
Yes, we're setting up a tightly controlled network, measured with GPS, TS and level, it will be least squares adjusted using SALSA. We need it tight, otherwise we'll have obvious misalignment in our scans, as we rely on occupation point and backsight for the scan alignment, we're not using cloud to cloud, the customer also wants it accurate, they wouldn't be very happy if our tolerance was a foot and scans in different areas, at different times were out by a foot. If our measurements are out, we'll know about it.
If we scan a long conveyor run, we're pretty much dependant on GPS at each end to tie it in.
That's about as much as I can tell you.
Up where? On top of a pole mounted on a building?
What is the configuration of your permanent gps base station?
If it's not an off-site deep-drilled and braced monument like this:
NGS.NOAA.GOV
Then you won't get even close to the type of results you're aspiring to.
@michigan-left Metrology
@jitterboogie Awesome, thank you, I know nothing about it, I'll do some research to help me understand and find someone local who does.
Cheers,
Peter.
what you need to provide the data you want is a full up gravity survey.
I got started in gravity, and it's used to detect and define subsidence and position of the oil fields in the Kingdom.
They are essentially are injecting sea water to surround and keep the fields under pressure with all of the massive extraction.
Company I worked for did a year long gravity survey for them to utilize for exactly what you're describing, except not for mining. It's also not published from what I remember, and that's what the client wanted.
Yeah, the Zephyr series of antennas are supposed to be superior to the old choke ring set ups, we used them for everything we reduced as our base antennas.
Sounds like interesting work, but don't reinvent the wheel if you don't have to. Just add some paint and fringe.
Yes, we're setting up a tightly controlled network, measured with GPS, TS and level, it will be least squares adjusted using SALSA. We need it tight, otherwise we'll have obvious misalignment in our scans, as we rely on occupation point and backsight for the scan alignment, we're not using cloud to cloud, the customer also wants it accurate, they wouldn't be very happy if our tolerance was a foot and scans in different areas, at different times were out by a foot. If our measurements are out, we'll know about it.
If we scan a long conveyor run, we're pretty much dependant on GPS at each end to tie it in.
Just for some clarification, if misalignment has been caused by recent subsidence (rather than a measurement error on our part), they will want to understand and know about it, I'm assuming they'd be more concerned about subsidence under a surge bin, than a conveyor, but I guess that would matter too. In that case, they might need to inject concrete under foundations for stabilisation, or they might need to relevel the conveyor, before it causes problems, when it fails, it's on a Friday afternoon or weekend and no one's around to help.
Choke ring vs non choke ring. If you take your antennas no matter which one zepher geodetic or choke ring. You need for what you are doing is to have an absolute antenna calibration performed on your antenna or antennas. They produce this at igs and such. Here is the thing. There might be one already listed for your model. But the reality is even the same manufacturer same model no 3 antennas will match perfectly. Even a relative antenna calibration can show as much as 3mm difference between same exact model.
the next thing i would experiment with is doing 4 hour observations take your existing 24 hour files and shorten them to 4 hours. Take the velocities that you can get from igs or your area. Ad break them down to build a model over your 7 day time period apply those to the 24 hour files you have broken down to 4 hour files. Find the sweet spot in how often is needed to do this. Now you can start applying the weighted averages and velocities and most assuredly apply the eop values. See how that works with answers you already have data for. So you have no re work just doing this. The other is time. What clock steering are you applying to your receiver is it just what’s built in or do you have the ability to get cesium and or rubidium information. To get where you want truthfully you will need to be modeling that information as well. If i am understanding you correctly. I might not be. Clocks in the receivers are not that good that we get from manufacturers. Good enough for what we do but not in the very scientific sense. Timing has a tremendous play when we get down to brass tacks.
if you can monitor 24/7 and begin to build this over time you can get some very good prediction parameters solved for on velocities and other anomalies. But it takes a long time to get it solid. It’s fun doing it though.
@pfirmst One thing is certain; in the big mines there will be movement.
We saw that often during our mine survey days. Control could move feet without any visible ground disturbance. It's part of the process. Doing what you're doing will be valuable to the mine. GPS allows it and I think you're on the right track setting up the system you are.
I know the type of conveyor you're talking about and those things are no joke.
Mines in Nevada have shifted water tables for the region. yeah, the impact is beyond the line of sight generally and hard to fathom.
@jitterboogie Unless the coal seam daylights there is normally water and methane trapped there. Dewatering will have to happen and it can effect large areas. Massive drag-lines and huge shovels aren't bob the builder equipment. There is a reason for left hand driving in the big mines.
yep.
worked on some of the biggest ones in the world.
truck tires that cost more than twice what most normal people make in a year.
The other is time. What clock steering are you applying to your receiver is it just what’s built in or do you have the ability to get cesium and or rubidium information. To get where you want truthfully you will need to be modeling that information as well. If i am understanding you correctly. I might not be. Clocks in the receivers are not that good that we get from manufacturers. Good enough for what we do but not in the very scientific sense. Timing has a tremendous play when we get down to brass tacks.
Thanks @OleManRiver, something else I didn't know was even possible. Yes, just the built in timing, clearly I've got some more homework to do. I'm realising after experimentation that the reports from AUSPOS, CSRS-PPP and other online processing services are a little optimistic about their levels of confidence. I'm not criticising them, just something I wasn't aware of until recently.
Nothing to do with GPS, just a few photo's from the past.
A crane tipped over behind me while surveying a huge building. No one was injured but it was a bad day at the mine.
@pfirmst you are doing metrology measurements. Ok i have worked in that world with laser trackers etc. here is something you might look into since you are looking more about precisions than absolute accuracy. With your gps system. Look at a septreno receiver. They use to sell a dual receiver and you could run multiple antennas simultaneously so instead of cesium or rubidium clocks that system can cancel the timing issue for relative positions. So in theory you could have some antennas on said building. At each corner. Measure there placement with laser tracker so you have a very precise information. Then as they each are collecting each antenna at different locations are tracking satellites and all at same exact time in receiver so there timing issues are no longer between each other. Except for the small delay you can correct for if even necessary of the differences along the antenna cable differences. You will have an independent positions from laser tracker to weight the gps positions against xyz. From laser tracker. You can monitor tgat over time as well so you can see if building is flexing during temp changes etc. i am thinking outside the box but another solution would be to tap into is machine control algorithms for blade tilt etc. they can have two receivers on a dozer blade and compute the slope etc. maybe you can use some of that and modify it for your uses. Its all math and such.
get the two or 3 antennas all repetitively calibrated against each other so you can deal with the antenna offset variations correctly. You might can just do them yourself if you look at the math from ngs site as you are already collecting 24/7. Choose one as gospel and go through the motions on the others.
