Wednesday, March 10, 2010

Create a digital elevation model (DEM) from a LAS file with FME

I am quite impressed with the capabilities of the surface generation and raster manipulation transformers in FME. Coupled with the rich set of vector feature transformers, you could almost put together a terrain modelling and image processing package. I tried out generating a terrain model in ESRI ArcGrid ASCII format from a LiDAR LAS file and I am quite happy with the results. To do a simple transformation, just do the following:
  1. Start up FME Workbench and create an blank workspace. Choose Source Data | Add Source Dataset.

    The Add Source Dataset dialog box appears.

  2. Choose ASPRS Lidar Data Exchange Format (LAS) in the Format drop down list. In the Dataset field, click the Browse button and select a LAS file e.g. 288_4320.LAS. Click OK.

    The Select Feature Types dialog box appears.

  3. Toggle off header and variable_length_header (optional). Click OK.

    The source dataset is added to the workbench.
  4. Select Destination Data | Add Dataset.

    The Add Destination Dataset dialog box appears.

  5. In the Format drop down list, choose ESRI ASCII Grid. In the Dataset field, click Browse and choose an output folder e.g. C:\data. Click OK to close the Add Destination Dataset dialog box.

    A message appears to confirm the addition of a new feature type.
  6. Click Yes and OK to add a new Feature Type to the workbench.

    The destination dataset is added to the workbench.
  7. Drag and drop the RasterDEMGenerator transformer and connect the source and destination datasets with the transformer as shown below.

  8. Open up the RasterDEMGenerator Parameters. In the Output DEM X Cell Spacing and Output DEM Y Cell Spacing fields, type in a cell spacing value e.g. 1 as shown below. Click OK.

  9. Run the translation.

    The ESRI ASCII ArcGrid DEM file is generated and can be displayed in a terrain model viewer.

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