This is a problem I've been having for years and it can't be just me.?ÿ Let's say we're surveying a platted lot somewhere from an old plat that's been drawn with great care (it's "perfect" geometrically/mathematically).?ÿ Normally, I bring in the field points from the TS, GPS, or whatever into a AutoCAD drawing.?ÿ Then I draw the plat or survey or whatever according to the record data to make sure it closes. Then I take the plat and manually slide it around and rotate it until it fits the most amount of pins within whatever the acceptable tolerances are, so I can analyze if all the found pins are in harmony relative to each other, according to the record.
However, I always have done this manually and it's more of an art than a science.?ÿ Tons of trial and error, and lucky guesses until I get the drawing in a place where all the linework corners are within a few hundredths of my points.?ÿ Hopefully this makes sense so far.
There's got to be a better, more technical way to do this though.?ÿ Isn't there a least-squares process (or other automated process) where you could hold all the record angles and distances (no scaling, compass rule, etc.) and have the computer go through all the iterations until it gets it in the best position without altering the record angles and distances?
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That would be pretty slick if there was such a thing.?ÿ I believe there is a best fit routine in Civil 3D that can sort of do this with individual lines but I'm not sure if it would work with polygons.
Primacode Transform does this better than anything else I have found.
2D conformal best fit, tells you statistics on rotation and scaling. Very quick process to see which monuments fit and how well.
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SurvCE?ÿ ?ÿ Transformation > Align does this. You can see the residuals and turn off the big ones. To be used with discretion of course. Can anyone tell me is it a LS solution??ÿ
I have asked Carlson SW about this in Carlson Survey but it's not there.?ÿ
What I usually do in the office is draw a pline star to all the field points, then move/rotate to a best fit like Mr. Wrench says. I don't like moving points so much until I have a solution.?ÿ?ÿ
You can fool StarNet into doing this sort of thing through the use of "Mapmode" data entry and some zero length ties to monuments but it is usually more work than I am willing to do.
What you are talking about is called a "Helmert Transformation". There are some Excel spreadsheets available for downloading but I can't vouch for any of them.?ÿ?ÿ
I should also mention I've spoken directly to people from Carlson and StarNet about this, and they both had no idea what I was talking about and/or no idea how to do it with their software.
The process I'm picturing would be to bring in the points you shot, hold them as "control" and key in the plat somehow as a traverse, and match it up that way (in a least squares sense), while holding the angles and distances (move and rotate only).?ÿ This would be a 2D only transformation.
But there's lots of good suggestions here I'll have to investigate.
I use a helmert.lsp routine to get close.
I posted this in 2016
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In SurvCE you ADD source and Destination point pairs. You can choose to scale source points or not. Just coordinates, no angles or distances. I want on my desktop.?ÿ
Then I take the plat and manually slide it around and rotate it until it fits
Do you create a block, out of your plat line work? That's what I do; I even do it with the surveys I find. I copy the block, then I can move it around, rotate, scale, all different kinds of ways, while keeping the original, just like it was. I can even explode the block, add new lines, and recreate the block; and it will reflect in the translated, rotated, scaled blocks I'm working with.
Is this the basis of your question?
Lots of other good routines suggested here; use those, if that was what you're after...
Dougie
Back in 1994, in Chilliwack, British Columbia, we would check our plat corner staking by setting up on a random point and tying all the corners we had set. Back at the office we?ÿ would use a program called "Rapid Transit" to best-fit the random setup ties to the record coordinates and generate a report, real slick.
These were the DOS days, 14" monochrome monitors, no network. AutoCAD was in its infancy.?ÿ "Rapid Transit" was a CAD and calcs program indigenous to the?ÿ Lower Mainland area of B.C. I never heard of it getting any traction outside of B.C.?ÿ ?ÿBut I now see that another B.C. based software company - Microsurvey - has a product with such a function. So maybe there is some relationship there.
Check out this youtube on Helmert Transformations in MicroSurvey CAD.?ÿ I think that this may be just what you are looking for.
Here is a similar Youtube for Carlson's Deed Correlation.
Do you create a block, out of your plat line work? That's what I do;
Same.
I have read this can also be done in TBC, but I never tried it and do it mostly in acad using the 'align' command to scale and rotate.
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We do this sort of thing regularly, using the least squares transformation routine in Topcon magnet. Its more commonly used for fitting fieldwork data to control points post survey, but can also be used to "best fit" occupation or title pegs (I'm not in USA) to a subdivision layout. As long as you know the limitations and are careful. Can be done in real time in the field too. (We sometimes work in new estates where we can shoot a bunch of title pegs and let the the software do a "best fit", turn off any bad residuals, and away you go?ÿ
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I have been using Triad to do this since some time in the mid '90s.?ÿ It is not magic, but can save a lot of time.
https://www.mcgee-gps-triad.com/win_triad_typ_apps.htm
Ken
I remember having a DOS program developed in-house. Input file was plat coordinates and field coordinates. It would rotate and translate and scale the plat to the field. You could also force scaling to be zero. It would return two "center of gravity" coordinates as well as rotation and the delta in the values.?ÿ
It was a great tool that we used often to come up with tighter search coordinates, or depending on the errors , fit the record to the field.?ÿ
Here is an output file.?ÿ
Carlson has the Deed Correlation command under the Survey menu that does exactly what you are asking for.
The Primacode program works great at this task. It's standalone from CAD. You work with coordinate files. Extremely flexible and capable software. I actually beta tested it for the developer, way back when.
I've mainly been using the Carlson routine Points > Adjust Coordinates > Coordinate Transformation since I don't have Primacode available where I work now. This routine works almost as well, but has the advantage of being integrated into the CAD software, so no need to import and export coordinate files. An advantage that Primacode has is you can apply different weights to the monuments. Found a bound leaning, or flopping loose in a mud-hole? Apply a lesser weight. In Carlson, you can only include or exclude a monument point from the solution. All monuments get equal weight in the adjustment. I have not found this to be too onerous to work with.
@dougie Yes, the process you described is exactly what I do.?ÿ It requires a lot of guess work and a heck of a lot of inversing between the drawing and points every time you move or rotate it.?ÿ I'm trying to automate the process.
I may not be completely following your problem, so forgive me if this is a random, irrelevant post.?ÿ I create the record linework prior to the survey and create my record corner points from that.?ÿ I usually also add as many record adjoining corners as possible and link both the corner point file and dxf into the DC.?ÿ The plat (or deed) should have a POB and ideally I find that on the ground.?ÿ If so, I setup up using 'refline' with that POB as the initial shot and the 2nd corner (if found) as the refline.?ÿ That way (in a perfect world) my field points are shot in their 'perfect' location and orientation, with ground shots to any corners found.?ÿ Of course I rarely find the POB corner in the field.?ÿ In those cases I proceed from whatever corners I can find (usually with a resection) and do something like what you're describing.?ÿ I my case as a C3D owner I use the align command with no scaling -?ÿ if the POB was found it gives you a pretty good start for evaluating record vs ground (depending on the basis of bearing).?ÿ If not, I'll align to the 2nd record corner, 3rd, or whichever was the first one I was able to find (in our state, clockwise).?ÿ In the case where the original POB was not found and used (which is most of the time) I would (I suppose, I'm not at this point yet) have to examine the deed and follow the footsteps, which I also suppose can drag you into examining several deeds/subdivision descriptions that are relevant in order to stick the POB in it's original position, whether it's done physically in the ground or just virtually on your map.
Michael McGee wrote a program called Triad
Point pair a record pt, to corresponding field pt.
best fit translate/rotate/scale. Many options to control this step.
Adjust entire data set to the point pairs.
We use it on every survey.?ÿ
google McGee land surveying, santa barbara.