I have Lidar LAS files in UTM18 and need them in State Plane. Horizontally they come in fine to a drawing with the correct system set. Vertically they are still in Meters. I know a couple of workarounds. But I'm just wondering if there have been any advances in 2014.
We're still on 2012 but I'm testing 2014 I don't want to go through the whole process again if it's not going to work.
Civil 3D 2012 SP 3 / IDSP 2014 HF1
Dell Precision T7400, Xeon CPU 3.16 GHz
Win 7 Pro, 64-bit,12 GB RAM, Nvidia Quadro FX 4600
AFAIK it doesn't.
One of the workarounds is to bring the data into Infrastructure Modeler and then export it to IMX. However I've found that you can't clip a surface that is imported from an IMX file. What is your workaround Allen?
One workaround would be to use Corpscon to convert the LAS file if they're in ASCII. These don't seem to be, but I'm trying to see what Corpscon does with it anyway.
The other is to complete the surface in UTM18 and meters. Then XML it out and XML it into a State Plane US foot drawing.
Just got an error from Corpscon. So that's not an option.
A more common challenge for me is transforming NED files. I have not found any software that performs vertical transformations on NED files. Since NED coverages are in 1 degree tiles they take forever to process and overwhelm C3D. If the workflow requires processing the data multiple times (i.e import/export/import) it is simply too prohibitive. Until we get support for vertical transformations I need to find a way to pre-process this type of data.
I found a method in 2012 that works. Should work in 2014 too, but who knows.
Export the Surface to a DEM file in the original system then create a Surface from the DEM file in the new drawing. Watch out because you'll see the input dialog will read the zone from the DEM file. But you sill have to enter it yourself in the fields below. Why? I don't know.
I tried using an XML file which theoretically should work, but didn't. Does anyone know the proper workflow for that?
Are you sure the vertical units will be transformed when importing a DEM? I had problems with that in the past.
I wasn't able to make an XML file work either. I've spent many hours looking for a solution to this transformation problem.
Are you sure the vertical units will be transformed when importing a DEM?
I have polyline contours in the same area that were done from photogrametrics 13 years ago. In areas where no construction occurred. The contours created from the transformed DEM file compare well. At least well enough that I'm sure I'm in the correct datum.
The key was realizing that I had to input the DEM file coordinate system in the import dialog even though it showed that it was reading it correctly from the file already.
It's almost as if anything to do with elevation transformation is purposely hidden. In the Export Points dialog box under advanced options the first choice of 3 is "Do elevation adjustment if possible" in both 2012 & 2014 help only the 2nd and 3rd options are covered. The first isn't mentioned at all.
I just found it described in 2013 help. You have to have created a point file format with a datum boot value. So it isn't useful for this type of transformation. But why is it not in 2012 help, in 2013 and not in 2014? Weird.
OK. I finally settled on a method. Takes a long time but gave me the best results. I extracted the points from the metric Surface. I converted the resultant AutoCAD points to Cogo Points (took 45 minutes for just under 130,000 points - did this during lunch). I exported the points to a NEZ csv file format and use Corpscon to convert it to my desired system.
I then used the point file that resulted from that conversion to build a Surface in my State Plane - US Foot drawing. That produces the best Surface. It's a little ragged but much better than any of the others. I can improve it with breaklines from another source and eventually with Survey.
Does the 45 minutes cover the whole process or just converting the points? If the latter, how long would you estimate the whole process takes (create the surface, extract the points, convert the points, export to csv, process in corpscon, build final surface)?
When it comes to DEMs, 130,000 points is a small dataset. Can we assume the process would take 5 times longer if the dataset is 5 times larger?