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Using Landsat Data FAQs - 15 Found

What are the gap mask files that come with Scan Line Corrector (SLC)-off Landsat 7 images?

SLC-off Gap Mask Files

Band-specific gap mask files are included with every Scan Line Corrector (SLC)-off standard Landsat 7 data product. These ancillary data files allow users to identify the location of all pixels affected by the original data gaps in the primary SLC-off scene.

The gap mask is provided as a series of individual band files, in compressed (GZIP) GeoTIFF format.

Figure 1. Sample SLC-Off to SLC-On gap mask


Gap Mask Legend Values:

  • green = primary scene
  • blue = fill scene 1
  • yellow = fill scene 2
  • pink = fill scene 3
  • red = no data (not filled)

For a standard SLC-off product, the data values contained within the gap mask file are as listed below.

0No data (data were missing in the original SLC-off scene)
1Populated data (data were present in the original SLC-off scene)

Gap mask files may not be included in older SLC-off scenes that have not been recently processed. You can create gap mask file by reviewing the information provided on this USGS Landsat Missions FAQ website.

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