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Challenge: Reverse Engineering a custom projection

  • December 11, 2017
  • 1 reply
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jstanger
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I have an interesting challenge. I've been provided an AutoCAD DWG with blocks placed using an unknown (an so far unable to be determined) projection and asked if I can take some source data in MapInfo (GDA94) and place it onto the DWG. Obviously without knowing the projection its not a trivial problem to make assets line up.

What I am able to do is in the source data identify objects that exist as blocks in AutoCAD and match on feature attributes. This gives me around 3,000 common points with locations in the unknown coordinate system relative to the known source data. I thought I might be able to use the rubber sheeting transformer to create a transformation that would simulate a reprojection but the closest I've managed seems to result in the geometry being stretched in the y-axis by around a factor of 2 to 5.

Am I just looking down a fruitless path or is there some hope? Can anyone suggest an alternative approach given the ability to match two sets of points within the two systems? I am able to bring Python to the problem if FME OOTB doesn't have sufficient tools.

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1 reply

takashi
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  • takashiCelebrity
  • 7843 replies
  • December 11, 2017

Hi @jstanger, I think the RubberSheeter should work fine if the Control vectors have been created properly from the common points. How do you think about the reason why the geometries have been stretched along the y-axis unexpectedly? How's the x-axis?

Why not inspect features with Visual/Data Preview and Feature/Record Information before writing them into a destination dataset?

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