California Surveyors Forums

TGO can produce a loop closure report, which you can set to your own specifications. Typically we use a 4 sided closed figure and you can set your closure error tolerances to whatever you wish. We usually run this report on the processed baselines before adjustment. I'm not familiar with the other GPS softwares out there.

Greg,

Just when I was really getting to like you...I'm a GPS Surveyor, too and proud of it!

(Picture that stupid commerical where people are yelling out the windows about deserving their legal settlement)

Ric

Who are Roger and Allan and what do they say about RTK boundaries ?

We use rtk all of the time with very good results. Like Greg says . . . any tool in the hands of the ignorant can be abused etc.

Close attention must be paid to each observation AND redundancies must be performed.

We are alerted on the spot of RMS or other issues. Remeber your "ree rees"
ReeVisitation, Reeobservation and Reedundancies.
In todays global SV saturation, the art of Mission planning is dying out like the plumb bob.
Also Carry a total station for those tough shots.

Hey, Greg!

I remember one frustrating site where one of my guys sat on a spot for a few hour long sessions. Everytime, the data from his receiver, no matter which one, proved to be garbage.

I finally sat withhim as he set up and ran the session. The point was in the painted median on the road. He'd pull up the truck with the big camper on the back and park it next to the receiver to protect it. Turned out that the camper was playing heck with the signals and giving us garbage.

A single half hour session with the truck parked on the side of the road proved to be golden.

It IS all in the details!

Yeah, so have I. Learned to park the truck (with the shell) away from the tripod.

Greg, I have heard Roger and others talk about their experiences multiple times and they have proved very helpful indeed in how I implement my procedures and techniques over the years. I use RTK and Static procedures interchangably in the vast majority of my work. I struggled through with learning postprocessing and testing RTK results against Static and traditional methods.

You have to admit...when using RTK early on and trying to get a simple topo shot in questionable coverage...you tried standing out in the "clear", fixing good, then "running" back in to try and get the shot before it changed to "float"! Go ahead, admit it...everyone has tried that. Only to find out later that your shot was about 5-10' off. I laugh every time I hear that.

Ric

I like using a modified 4x4 method explained to us by a very smart surveyor (M.McGee). You can certainly tie out monument with RTK, but don't tie it out just once! Here is what we do:

1. Shoot it, (usually a 1 minute RTK Shot: Good time to take notes that will later be scanned and stored in the job file) and then "break" the radio link (This means inverting the rod and loosing satellite and radio link forcing you to loose the mathematical “integerâ€￾ solution). 2. Rotate your rod 90 degrees. Re-initialize and shoot it again for a few seconds. 3. "Break" the radio link. Rotate you rod again by 90 degrees. Re-initialize and shoot it again for a few seconds.

Now you have 3 shots on the point. Doing this takes a little longer, but it's the only thing we have similar to "double an angle" for RTK work. It checks your rod calibration (rotating it so see a difference), and checks the "integer solution" of the RTK. The odds that you'll get the same erroneous integer for the same point are astronomical. What that means is you're getting some interference or bad data because of multi-path or other factors, it will give you two very difference coordinates for the same position, and now you know there is a problem! The third shot should the deal maker, unless the rod is out of plumb, and you’ll have to make a hard decision weather to mean them all or just do the right thing and shoot it again (with a calibrated rod).

In addition, I usually introduce other network redundancies such as cross ties and maybe shooting some of the monuments with both RTK and Static. I process the vectors and input them into Star*Net and get viable error ellipses and remove blunders. You should see up to a tenth for vertical measurements and within .03’ for horizontal.

This process works. I've caught a bad integer (under a tree) and I've caught out-of-plumb rods. It's really the only way to check to see if the crew is got the equipment and methods under control and calibrated.

I’ve found the no. 1 culprit to be out-of-plumb rods. They guys are really hard on them and they simply need check every day before starting a survey.

I took a look at this post after Scott mentioned the thread in his lot closure thread:

"I just got the first set of requested revisions back from a certain city for a simple Parcel Merger. Two rectangular lots being consolidated into one. Same individual owns both.

The closure around the merged parcel was “perfectâ€￾ (1:INFINITY). It is a rectangular lot – opposite sides parallel. That’s not good enough. The closure has to be expressed in…


wait for it…


THOUSANDS OF AN INCH!!!

I’m hoping this is an error on the part of the reviewer…We’ll see tomorrow."
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At the risk of appearing as a "Disputatious Individual" I feel compelled to make the following comments:

It appears that the implication here is that since the project consists of a "simple parcel merger" and the "same individual owns both" (parcels) that verifying the closures of the parcels is somehow simplified. It might make the surveyor's job easier but it doesn't help the closure checker any.

Also, the subject parcel is described as being a "rectangular lot --opposite sides parallel". However, upon inspection, the lot has two opposing sides that are nearly three degrees out from being parallel. The other two opposing sides are within 4" of being parallel, but are over a thousand feet in length. When trying to meet a closure requirement of .02', the 4" of angle becomes a factor. As a result of these discrepancies, determining whether the parcel meets an acceptable closure or not does not appear possible from "inspection" alone, no matter how experienced the map checker is.

If the published bearings and distances are used for checking the combined parcel, the error of closure is approximately .004' or roughly 1:650,000. Certainly good enough for most of us, but not quite "1:infinity" that the cad generated report indicates. The cad program is not using the rounded values in it's comps and when the closing point selected is the exact same point as the starting point, you should expect a mathematical misclosure for the polygon that is approaching the reciprocal of infinity, or as close to zero as you can get, given the limitations of the computing software.

That being said, I don't see why it matters if the closures are calc'd using the unrounded values, as long as the courses on the map agree with the closure sheets, and the resulting closures meet the required standards.

In partial defense of the lowly map checker, I suspect that "Junior" meant thousandths of a foot instead of an inch. Inches, and even thousandths of an inch are units that are commonly used in other engineering disciplines and in our everyday lives as well. "Junior" wouldn't be the first person to make that mistake in our profession, and he probably won't be the last. Also, he probably had a check list that required misclosures of no more than .02 feet or so, and wasn't used to seeing the results in a ratio format. I would feel fortunate if those were the only comments on my submittals worth complaining about. Futhermore, it appears, solely from "Junior's" immaculate hand writing alone, that he is probably in the engineering/surveying field (not a planner), is educated beyond the high school level, and takes a lot of pride in his work. The word "professional" comes to mind just from the appearances of his printing alone. Don't you think we should cut him a little slack?

I check my bubble weekly and most the time I am half a bubble off.