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I have made quite a big georeferencing error, by attributing one of the control points of the map with a value that is 2 km less than the actual value, on the horizontal axis. The georeferenced map looked more like a right-angle trapezoid. I realized this only after digitizing, so my question is, can I tweak/adjust somehow the digitized lines so they become correct according to the new shape of the map?

I have imagined rescaling around a point that is different than the center of the map, in Global Mapper, but I seem to be long way off achieving anything.

Thank you!

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Something to think about is looking at how many features you have digitized. If you are talking about a huge number, and by that, I mean hundreds to thousands, then it is probably worth pursuing an automated solution. If it is less than that, it is potentially worth simply digitizing them again based on the correctly georeferenced basemap. Sometimes, simply starting over is more efficient than trying to fix an error. This doesn't seem like it will be a simple fix either, as you have multiple directions and amounts of skew that have to be corrected for. –  Get Spatial Sep 30 '13 at 1:42
    
I have more than 1700 contour lines, so i have to make it automatic. And that is what i would like to do, or to find out how. I am working on ArcGIS. There i digitized and i might try spatial adjustment, maybe rubber sheeting could do the trick. A friend told me i could regeoreference the vector data, but that still gave me errors of ~70 m. I would like it to have less, around 20 m, if possible. –  Paul Nicoara Sep 30 '13 at 19:47
    
Well, i am happy to say it was easier than i thought to get to 20-30 m of error, by the method i described earlier (rubbersheeting). I only had to put about 60 displacement links. :) –  Paul Nicoara Sep 30 '13 at 21:01
    
Glad you were able to fix it. You should write up what you did as an answer to this question. You may have to leave it a couple of days, but then you can mark it as the accepted answer for your question. –  Get Spatial Sep 30 '13 at 21:09

2 Answers 2

So the solution was like this: First, regeoreference the raster. Second, using Rubbersheeting transformation in the module Spatial Adjustment in ArcGIS, while being in an editing session, place several displacement and identity links all around the edges of the map. You need displacement links for the data that will be modified (in my case, strechted) and the identity links for the ones that will remain in the same position. I also placed a few inside the edges. The more you place the more accurate it will do the transformation. I placed arround 60 and got my errors down from 2 km to 30 m.

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You can always fix the control points and edit them as required.

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I have already digitized based on the wrongfully georeferenced map, so now i want to modify the contour lines created. I have no fix control points on them. –  Paul Nicoara Sep 30 '13 at 19:44

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