Landsat Missions
Band-specific gap mask files are included with every Scan Line Corrector (SLC)-off Level 1 Geometrically (L1G), Systematic Terrain (L1Gt), or Terrain (L1T) corrected standard or gap-filled product. These ancillary data allow you to identify the location of all pixels affected by the original data gaps in the primary SLC-off scene, prior to any interpolation and/or gap-fill associated with Level 1G processing. For an SLC-off gap-filled product, the gap mask will also provide a record of the original data source for each pixel.
The gap mask is provided as a series of individual band files, in compressed (GZIP) GeoTIFF format.
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Figure 1. Sample SLC-Off to SLC-On gap mask |
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Figure 2. Sample SLC-Off to SLC-Off gap mask |
Gap Mask Legend Values:
For a standard or interpolated SLC-off product, the data values contained within the gap mask file are as listed below.
| Value | Meaning |
|---|---|
| 0 | No data (data were missing in the original SLC-off scene) |
| 1 | Populated data (data were present in the original SLC-off scene) |
The potential data values contained within the gap mask file for gap-filled SLC-off products are listed below.
| Value | Meaning |
|---|---|
| 0 | No data (data were missing in all scenes) |
| 1 | Primary scene (data contributed by original SLC-off scene) |
| 2 | Fill scene #1 (data contributed by fill scene #1) |
| 3 | Fill scene #2 (data contributed by fill scene #2) |
| 4 | Fill scene #3 (data contributed by fill scene #3) |
| 5 | Fill scene #4 (data contributed by fill scene #4) |
| 6 | Fill scene #5 (data contributed by fill scene #5) |
The potential data values contained within the gap mask file for Segment-based Gap-filled SLC-off products are listed below.
| Value | Meaning |
|---|---|
| 1 | Non-gap pixels |
| 2 | pixels filled with scale 10 segments |
| 3 | pixels filled with scale 15 segments |
| 4 | pixels filled with scale 20 segments |
| 5 | pixels filled with no scale (nearest neighbor) |
Scale 10 – smallest segments with the highest accuracy; approximately 80% of the gap-filled pixels should be filled at this scale
Scale 15 – larger segments with less accuracy
Scale 20 – larger segments with less accuracy
No scale – a very small percentage of pixels may be filled at this scale
A SLC-off gap mask is included with any of the SLC-off products that are downloaded from the Sample Products page.
U.S. Department of the Interior |
U.S. Geological Survey
URL: http://landsat.usgs.gov
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Page Contact Information: landsat@usgs.gov
Page Last Modified: May 09, 2008
