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Crop Agriculture

Image Availability: Two Main Considerations

Related Page: Landsat 7 & 8 Scene Overlap & Download

Depending where a location is relative to Landsat scene extent has a lot to do with how much imagery will be available.  

One main consideration, in regards to all Landsat satellites, is that there is an overlap area with neighboring images on the east and west sides of about 50 km (there is a much smaller overlap area on the north and south sides). If a location is within this area, it has a greater chance of clear imagery being available.

 

 The graphic below shows Landsat scene boundaries and the overlap area

 Landsat scene boundaries and the overlap area

 

A consideration specifically in regards to Landsat 7, is that in 2003 it developed a mechanical problem that created stripings of missing data that start near the center and increase in width towards the east and west edges of a scene. There is, however, a north-south center section about 22 km wide (13.4 miles) free of this problem. It is better if a location is within the center area (between yellow lines below) where there is no missing data and it is worse if it is further to the east or west where the amount of missing data increases. The maximum width of the data gaps along the edge of the image are approximately 390 to 450 meters. The precise location of the missing scan lines can vary from scene to scene.

Landsat 7 center area without missing data

Image above is from USGS (2010) showing area where there is no missing data for Landsat 7. A Landsat image (scene) is about 185 (e-w) x 175 km (n-s) (115 x 106 miles).

 

 Below is center area of a Landsat 7 NIR image (different image than one above)

Landsat 7 center area without missing data

 

 Below is eastern edge of Landsat 7 NIR image (same image as one immediately above)

Landsat 7 stripings of missing data widens towards east and west sides

 

Landsat 5 TM was launched in 1984 and was only designed to have a 3-year life span; remarkably the satellite only stopped acquiring imagery in 2011 (24 years longer than expected) so there is a large historic archive. Landsat 7 ETM+ was launched in 1999 (Landsat 6 ETM did not achieve orbit when launched in 1993) and was designed to have a minimum 5-year life span. Landsat 8 was launched in February of 2013 (has not acquiring imagery) and is designed to have a minimum 5-year life span. 

 

Reference

USGS. 2010. United States Geological Survey: Landsat Missions. SLC-off Products: Background. Cited at: http://landsat.usgs.gov/products_slcoffbackground.php.