I do not have a GIS background and was hoping that someone could point me in the right direction as to the best procedure / software to do the following.

Starting with a current LiDAR survey, I need to be able to compare an older survey (contours in a DWG) and create a composite surface that is the lower of the two at any point. These are both too large, and too close in elevation to deal with the triangulated surfaces in AutoCAD (which is my default right now). Also, moving forward I will have to continue to integrate new survey into this surface to maintain a "cleanup floor", which AutoCad does poorly, as it does not easily allow for just integrating the cut portion of any new survey.

My gut tells me there must be a simpler method to do this by converting them both into a uniform grid (DEM is the convenient output from AutoCAD), and then comparing them in a GIS software but I have no idea which software to go to, or what the simplest methodology would be.


Unfortunately, I don't have a clear workflow for you. But I would recommend trying FME workbench from Safe Sorftware. Usually you can build a workbech that can take various sources, in your case, Lidar and AutoCAD. Then you can process these and output some data (DEM-rasters probably in your case). One advantage of FME is that usually it can handle large datasets and it's easy to add new data and re-run the workbench to obtain the new results.

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  • Also note that they have a demo version, so you can test your workflow. – jeb Feb 26 '13 at 21:21
  • Thanks! This actually seems like it might do the trick for this issue and a few others I am having. – KRudolf Mar 5 '13 at 15:22

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