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I'm trying to generate a DTM from lidar data and I'm new in the this field.

I have different kind of files which describe the same area (different versions):

  • *.dtm
  • *.xyz
  • *.xyz with variable grid width (1 to 4 meter), according to the information sheet I have.

How would you handle each file format to get a DTM? Specially in the case of the XYZ-data with variable grid width, I have no idea about what to do.

Once you have the DTM, how can I be sure about the correct geographic position of the DTM?

I want to use the DTM to analyse the terrain. Which kind of format (of the DTM) would you recommend?

I use ArcGIS (with extensions) and would prefer a solution process on this platform. However, if there is an open source solution it's fine too.

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ArcGIS solutions:

Convert the x,y,z data to a feature class then:

  1. Build a TIN using x,y,z data and then convert this to a raster.

  2. Interpolate the x,y,z to raster.

  3. Use Anudem (topo2raster) to create a DEM.

  4. Convert point to raster and just set a cell size that is suitable for your x,y,z data (usually only for dense data).

I would output a GeoTiff.

x,y,z can be gridded hence you can use gdal and just convert to another format such as GTIff.
x,y,z can just be point data then use 1,2,3 or 4 above or GDAL Grid.

The position should be fine as you have x and y. You just need to know the coordinate system. You can usually tell this by looking at the numbers in the x,y column and knowledge of your local area.

I would be remiss not to point you to this question as well.

  • Thank you very much! this is a step forward! Do you have any ideas regarding the converting of the xyz-files with variable grid width? Is it possible to determine the resolution of the resulting DTM during the xyz-to-DTM-process? Thanks again! – Reen Oct 21 '14 at 10:40
  • yes you will get to select a resolution in all the above scenarios. I would have to see the variable width xyz file as this I am not familiar width. Post a link and I'll take a look. – If you do not know- just GIS Oct 21 '14 at 12:45
  • I've decided to create a DTM according this tutorial:STEP1 AND STEP2.Can you tell me when there exactly is the point to determine the resolution of the resulting DTM?I guess it has to do with the cellsize/sampling distance/etc but i'm not sure. During the process of creating a DTM you have to set this option several times.THX! – Reen Oct 22 '14 at 8:52
  • You have to infer this based on what you are studying, what features you would like to depict, the point density of the data and other considerations. No one rule exists. For example, if I was looking for archaeological features with sub-meter terrestrial scanning data it may be a few cm but if I was examining surface hydrology over a county with a point density of 1 per 3m2 then I would use an entirely different resolution. – If you do not know- just GIS Oct 22 '14 at 12:41

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