I am helping my neighbor and we set up a base on top of his shed. I collected 3 days of OPUS data and converted the solution to feet. I created a new job and loaded his stakeout points from his engineer and the coordinates for the base both via CSV.?ÿ
I started the base with the opus point coordinates and when I go to start the rover it gives me a popup message about the coordinates of the base point in the job differing from the broadcast coordinates. My only options are to cancel or use the database coordinate. If I hit the details I get a window that shows there is no horizontal difference and the vertical difference is 2.693 feet.?ÿ
I have never seen a message like this before and do a similar setup all the time. There is only one point in my job for the base and is named opus_feet all the other points have a 4 digit number for the name.?ÿ
Any ideas what is going on??ÿ
I have a point at my house I have ran multiple solutions on and I measured it using his base and the true coordinates are
| 908169.47 | 7227437.24 | 3270.617 |
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Off his base I get
| 908169.466 | 7227437.25 | 3267.869 |
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Horizontals virtually identical and the vertical is off 2.748 feet
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The only thing I can thing of may be the antenna height. It is nearly 16 feet. We entered it correctly but maybe the software can't account for a base that high?
Double check the antenna heights on your OPUS solutions and on your base, the error must lie in there somewhere.
The lesson here is use a zero height to the ARP when you mount a semi - permanent (or semi - temporary) fixed base. If you re-run the OPUS using zero to the ARP and then plug that in as your base elevation also at zero it will almost definitely make this problem go away.
If you want you can send me the files in question.
I can't find a combination that matches your difference, but I'm highly suspicious of antenna heights in feet, as OPUS works in meters.
As for using a 0.000 height, I tried that a few months ago and OPUS wouldn't take it.?ÿ I had to use 0.0001 meter
Bill: I have never had a problem using 0.000 m for an HI, it just gives a warning but once you hit OK it works.?ÿ
Thanks for the replies. I never thought of using a 0 (or near 0) ARP. That would make things slick.?ÿ
I did the feet to meters conversions and don't suspect any errors related to OPUS.?ÿ
The problem is with the data collector. It doesn't know or care if the OPUS solution is off by 2-3 feet. It reports a vertical difference of ?ÿ2.693 feet which is dangerously close to the 2.748 difference I am seeing on my measured point. 0.055 feet. RTK isn't much better than that on vertical is it??ÿ
What is your base antenna height--you said almost 16 feet? If there's a 4 meter maximum for base height, that would be 13.12 feet. That plus your difference might make sense?
The base is 4.8514 meters ARP. I enter it into the data collector as 191 inches which it displays as 15.917 sft
Interestingly this .8514 meters is 2.793 feet and it is telling me I am 2.693 feet off.
So I guess a possible solution or thing to try is to set my antenna height to zero on the data collector and add 15.917 feet to the OPUS solution elevation I use for the base point?
You have to be careful with antenna heights.?ÿ ?ÿI had a project and it drove me nuts.?ÿ ?ÿWhere are you measuring from and to.?ÿ ?ÿI know on my trimble antenna I measure to the bottom of the notch and also verify you have the same thing in your data collector.?ÿ It is so easy to switch from bottom of notch to one of the other possible measurements.?ÿ ?ÿAlso remember that opus works to the bottom of the antenna mount and not the notch on the antenna.?ÿ ?ÿAll those little things add up, not sure about 2.6 ft, but there is a problem somewhere.
I agree about where to measure and being careful but screwing that up wouldn't cause the message I am getting.?ÿ
I start the base and it starts normally. I connect to the rover and go to start survey and it pops up a message that the coordinates of the base point in the job and the coordinates being broadcast by the base are different.
If I measured to the wrong spot my data would be bogus but I don't think I would get an error message? I use this equipment almost daily and have for the past 4 years and I have never seen this message before. I have never had a base this high before either. I am thinking that might be the problem but not sure. ?ÿ
The base is 4.8514 meters ARP. I enter it into the data collector as 191 inches which it displays as 15.917 sft
Interestingly this .8514 meters is 2.793 feet and it is telling me I am 2.693 feet off.
"What's an inch?" ...as all party chiefs are obliged to ask when their new chainman utters the word.
The survey gods are?ÿobliged to punish anyone who measures in?ÿinches. ??ÿ
I've seen this message many times.?ÿ ?ÿDid you start the base from the same job??ÿ ?ÿ
After I had the opus solution I created a brand new job and imported the base coordinates as a csv.?ÿ
Not a Trimble user but I noticed in the screenshot WGS84.?ÿ The vertical difference noted is in the ballpark of the vertical difference I see between WGS84 and NAD83 observations on the same point. Just a thought. Don't know why the horiz. dist is nothing if this is the problem.?ÿ
The basis is what created the stakeout points. This is why site control is important.
Why have a 16' HI on a shed roof? What are you measuring??ÿ
I sometimes use my truck to hold the base, those set-ups don't get a valid HI, think of it as a resection point.
Forget OPUS, use the control that created stake out points, if there was a topo done, check into it.
The basis is what created the stakeout points. This is why site control is important.
Why have a 16' HI on a shed roof? What are you measuring??ÿ
I sometimes use my truck to hold the base, those set-ups don't get a valid HI, think of it as a resection point.
Forget OPUS, use the control that created stake out points, if there was a topo done, check into it.
There are several reasons for the 16' tall base. I am letting my neighbor borrow my spare equipment to do this. I don't have an extra tripod or an extra external base radio. He welded a 5/8" stub to mount the base on to in a fixed location. We needed height to get the low power radio signal coming directly from the R8 out across his project. He has a ton of big dirt piles, shipping containers, heavy machinery, cranes etc on site and this was about the only place that was taller than everything and would not be disturbed as the ground pretty much everywhere else is getting shaped.?ÿ
He is building his own house and it is in a flood zone. He is working with the engineers and has an approved plan to excavate out of the lake bottom area and build up the area for his house. It involves moving tens of thousands of yards of dirt. He does this in his spare time after work, on weekends, etc and there are places he is changing ground level 15 feet or so. Not really practical until he gets close to use grade stakes and he can't schedule the engineering firm which has surveyors to be there on the odd hours he is able to work on it so he needs a solution to be able to get things close him self.
The plan from the engineers which is basically an excavation plan is in state plane coordinates which are what we are using. The reason for OPUS is the elevations are what is really critical as he need to make sure his house and outbuildings are high enough to be out of the flood zone. The engineers did scribe a mark by the road and give an elevation for it that we check into to make sure we are on.?ÿ
Linebender may have it. Depending on your locale it could easily be a global versus local issue.
Many vendors (Trimble included) assume geographic coordinates are WGS84. One workaround is to set your datum to NAD83 using a molodensky 0,0,0 translation. Not purely correct but simple. There are about a dozen other ways to get it done...
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I have s base antenna on the roof of the office. We use a 0 hi at antenna phase center
