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