Landsat Missions
Question:
How do I fill in the gaps in my SLC-off image?
Answer:
NOTE: References to non-USGS products do not constitute endorsement by the U.S. Government.
For many, Landsat 7 ETM+ SLC-off data has been difficult to use due to a hardware failure that resulted in 22 percent of the data missing from each scene. The Landsat Project developed several products that minimized the gaps, the most popular being the “off-to-off” product that took two (or more) ETM+ scenes, radiometrically matched them, and then combined them for more complete coverage. Now that the Landsat Project is distributing orthorectified data at no charge, users can combine their own scenes with Commercial-off-the-Shelf software. Below, the directions for combining scenes in the Leica Systems ERDAS Image program are described. No-charge SLC-off data can be found at EarthExplorer and GloVis under the Landsat Archive collection. Please see ‘Which images will work best to fill in the gaps?’
Use model-maker to add each band in Image 1 to the corresponding band in Image 2. The following statement says:
Where Image 1 > 0, use Image 1 data, Otherwise, use Image 2. Image 2 data will fill the gaps in Image 1.
Use the following syntax (this example is for Band 5) in the model: EITHER $n1_l71015033_03320070515_b50 IF ( $n1_l71015033_03320070515_b50 > 0) OR $n2_l71015033_03320070531_b50 OTHERWISE
Then you can layer stack, or leave the files as individual bands. Note: these directions do not include radiometric matching.
While still having a small residual gap, the image below is two scenes combined (without histogram correction applied).
Figure 2. Combined scenes without histogram correction
U.S. Department of the Interior |
U.S. Geological Survey
URL: http://landsat.usgs.gov
Page Contact Information: landsat@usgs.gov
Page Last Modified: November 24, 2009
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