Cornell Library GIS Cookbook

Creating contour lines from .las LiDAR data

LiDAR pointcloud datasets are collections of three-dimensional x,y,z data, often distributed in LAS format with a .las filename extension. LAS files can be downloaded from sites such as OpenTopography.org and the US Interagency Elevation Inventory.

  1. After downloading the .las data, create an LAS dataset in ArcCatalog.
  2. Convert that dataset into raster format using the LAS Dataset to Raster tool (Conversion Tools > To Raster > LAS Dataset to Raster). You may need to define the projection.
  3. Then use the Contour tool (Spatial Analyst Tools > Surface > Contour) to generate your contours. You may need to first turn on the Spatial Analyst Extension from the Customize menu.
  4. If you need convert the contours into CAD format (optional), here’s how you can export elevation contours from ArcGIS to DWG as 3D lines:
    • In order to keep the z values, there must be an attribute field called "elevation".
    • The ArcGIS tool for generating the contours (ArcToolbox> Analyst Tools>Surface>Contour) creates a field called "CONTOUR", so all you have to do is create a new field called "elevation" and copy the values from "CONTOUR". The steps are spelled out in the pink box on this page.
    • After that, in ArcMap simply right-click the contour layer, selecting Data>Export to CAD… and select the latest DWG format ("DWG_R2010")