Building Footprint Extraction

The Building Footprint Extraction process can be used to extract building footprint polygons from lidar. It uses the building class code in the lidar to create a building footprint raster which then can be used to extract building footprints.

To extract building footprints, you will need:

  • Lidar with ground and buildings classified.

The Building Footprint Extraction process accomplishes the following:

  • Classifies buildings in the lidar (only required if buildings are not already classified).
  • Creates a building footprint raster.
  • Fills holes in the footprint raster.
  • Creates building footprint polygons from the footprint raster.

Classify Buildings in lidar

This step classifies building rooftop points in aerial lidar data and is only required if your lidar data does not have buildings classified (class code 6). Make sure you check the lidar before using this tool. LAS points with class code values of 0, 1, and 6 will be evaluated to determine if they fit the characteristics of building rooftops. Points classified as buildings that do not meet this criteria will be reassigned to a class code value of 1 unless the option to reuse existing building classified points is specified.

Clasasifying building rooftops in aerail lidar
An example of building rooftop classification.

Create Footprint Raster

Once you have lidar with ground and building class codes, you can use the Create Footprint Raster step to create a footprint raster. Set the Cell Size to the average point spacing of the lidar.

Create Footprint Raster result
Create Footprint Raster result.

Fill Footprint Holes

Depending on the lidar point spacing, the footprint raster will have holes in the footprints. Use the Fill Footprint Holes step to fill the holes in the footprint raster. Experiment with the Max Void Width value to fill the voids in the raster. The maximum void width value is used to specify the largest size of a void that you want to fill without merge buildings together. Lidar with higher point density typically requires lower max void fill values.

Fill holes in footprints
Fill Footprint Holes result with Max Void Width set to 15.

Create Footprints from Raster

Use this step to extract the building footprint polygons from the raster. The Minimum Building Area parameter controls the minimum area required for a building area to be designated as a building. For best results, use a Split Features polygon feature class such as parcels. Splitting can improve the regularization of the resulting building footprints.

Create footprints
Create Footprint from Raster tool.

The tool will also remove any holes in buildings that are smaller than this threshold. Optionally use the building parameters to control how various building forms are extracted.

Extract footprints
Create Footprint from Raster result.