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Question:

What is the U.S. Landsat ARD tile grid system?

Answer:

U.S. Landsat ARD products are processed to a common tiling scheme, and each ARD tile contains 5,000 x 5,000 30-meter pixels. The U.S. Landsat ARD tiling system is modified from the Web-Enabled Landsat Data (WELD) structure developed at South Dakota State University (SDSU) (Roy and others, 2010). The WELD-defined grid is similar to the National Land Cover Dataset (NLCD); however, WELD is based on the World Geodetic System 84 (WGS84) datum and NLCD uses the North American Datum 1983 (NAD83), causing an approximately 0.5 pixel offset in the X and Y directions between the two grids.

The U.S. Landsat ARD grid is anchored to the coordinates listed in Table 1. These grid origins are defined in relation to the WGS84 datum used by WELD, but are adjusted to align with the origin used by NLCD datasets. 

U.S. Landsat Analysis Ready Data (ARD) Tile Grid Extents

  Upper Left Tile (ul corner)   Lower Right Tile (lr corner)
  (h) (v) ulX (m) ulY (m) (h) (v) lrX (m) lrY (m)
CONUS 0 0 -2565585 3314805 32 21 2384415 14805
Alaska 0 0 -851715 2474325 16 13 1698285 374325
Hawaii 0 0 -444345 2168895 4 2 305655

1718895

Table 1. U.S. Landsat Analysis Ready Data (ARD) Tile Grid Extents

The U.S. Landsat ARD tile pixel dimension (number of columns and rows) is smaller than the dimensions of individual Landsat WRS-2 path/row scenes (Landsat 8: ~6300 x ~6000 pixels; Landsat 7: ~6,166 x ~5,666 pixels). 

  • 420 tiles cover the land mass extent of the conterminous United States
  • 110 tiles cover the land mass extent of Alaska.
  • 8 tiles cover the islands of Hawaii.

U.S. Landsat ARD tile grid shapefiles, maps and tile grid extents are available on the U.S. Landsat ARD webpage.