Masking or Clipping

In GIS, masking or clipping is selecting areas to be used for analysis.  It can apply to both raster and vector data, and removes from consideration all data that does not meet geographic criteria.   You will typically use another data set for the masking, and either remove or retain only the data that matches geographic criteria.

It is probably easiest to start with a vector shapefile, select a specific record, and then remove everything in the other data set not within the record.

Masking differs from filtering the database, which uses fields/attributes in the database to select or hide individual records.

Map of Anne Arundel County, Maryland:
  • NED DEM oritiginally filling a rectangular box, masked with the county outline.
  • Schools from the USGS Gazetteer for the state of Maryland, filtered to show just the schools, and masked to restrict them to the county.

MICRODEM options

last revision 2/17/2014