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rweiser
Posts: 7
Registered: ‎07-07-2003
Message 1 of 2 (47 Views)

Nothing simple about Simple Transformation!

47 Views, 1 Replies
12-26-2001 09:18 AM
Hi all..

I am reposting this question here since I did not get any responses in the "general" posts category. In a nutshell I am trying to attach a drawing and use both the offset and rotation values in the simple transformation drawing settings dialog box area to fit a single survey plat to a second, referenced drawing. I can do this quite easily by manually moving & rotating the drawing AFTER I've queried it in...but to get the drawing to pop in with rotation and offset already applied is surprisingly difficult. Apply either the offset or the rotation independently and no problems...try doing them both and lookout! Where is the rotation applied? Is it applied before or after the offset?

More detailed information is given below (more than you ever wanted!) Thanks for any help at all.


The Setup:


I have a survey in a local datum, no specific projection. Surveyor goes into field, sets up on a monument and calls that point 5000,5000 and then proceeds to gather points. I have another drawing set up in UTM, NAD 83 Zone 15, units in feet.


The Goal:


I want to be able to query the survey drawing directly into the UTM drawing without altering the original survey drawing.


The Approach:


I have tried a couple of things with partial success and the sticking point is in the drawing rotation. I've tried using the "Simple Transformation" setting under the Drawing Settings when I query the survey into the UTM drawing. I have also tried creating a custom projection where I am able to enter my own northings and eastings using a Transverse Mercator projection and the NAD datum.


The problem:


If I use the X,Y offset by itself in "Drawing Settings" there's no problem, but when I apply a rotation AND an offset, I run into difficulty. The main thing I am unable to figure out is where the drawing is being rotated..ie
about which point in the survey drawing is the rotation being applied? Can this point be specified or changed? The same basic problem exists in using the Custom Projection approach. Usually I try to find a common point that
can be identified in both the survey drawing and my georeferenced drawing for purposes of determining an X,Y offset value. Both may show a section corner for example. However if the rotation is applied at point 0,0 or at
the lower left corner of the drawing extents, or basically anywhere but at my common point of reference, the drawing offset at any other given point will change as a result. It would be incredible to be able to apply both an offset value and a rotation about a given point but I can't see any way of doing this.


Workaround:


I have not tried this yet, but I am thinking of applying an offset and rotation to get a bad fit, then measure the distance or error that results. I think I might be able to take this error value and apply it to my original X,Y offset in order to make the thing come in the proper
location but I'm not sure if it will actually work that way. In any event, it's a bit of a job doing everything twice and I'm hoping someone can shed some light on the problem.

Only other thing I can think of is to set the drawing's north rotation in Land Development Desktop, but I don't mess with LDDT2 too much and aren't exactly sure if Map even respects north rotation in a drawing.


Thanks for any ideas!

Ray Weiser
Contributor
gerardog
Posts: 12
Registered: ‎12-26-2001
Message 2 of 2 (47 Views)

Re: Nothing simple about Simple Transformation!

12-26-2001 10:03 PM in reply to: rweiser
Hi!
I don't have enough time to make a test so as to be sure of what I'm telling you, but may be what Map is doing is concatenating two matrices, one with the displacement and one with the rotation. I've taken a look to the help and it says that the rotation is the 0,0 point, so maybe this is how it works, and if it so, you may have to find the new matrices.
Hope this helps,
regards,
gg

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