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A nearly complete global data set of high resolution satellite photos
(Landsat 4/5 TM and Landsat 7 ETM+, bands 7. 4 and 2)
in MrSID format are available from NASA at:
https://zulu.ssc.nasa.gov/mrsid/. The same site contains
a
very good tutorial.
The images have the following characteristics:
- Pixel size (~resolution) is either 28.5 meters (for c. "1990"
data) or 14.25 m (for c. " 2000" data). The "1990" and
"2000" acquisition dates are +/- 3 years for both data
sets.
- Data are in UTM coordinates, WGS84 datum
- georeferencing information is stored in a world file with an .sdw
extension; format is typical six line, with last two lines
giving easting and northing of the center of the upper left
pixel of the image.
- images in the southern hemisphere have northings that are
NEGATIVE VALUES, i.e. there is no false northing of 10,000,000,
as per usual southern hemisphere UTM northings.
- Positional accuracy is +/- 50 meters.
These photos will not be georeferenced without first setting a
spatial reference (i.e. creating an .aux file).
To do so for an image in the NORTHERN
HEMISPHERE:
- while in ArcCatalog, right click on the file name, click
Properties..>Spatial Reference>Edit>Select and browse to the
appropriate projection (UTM, zoneXXN, WGS84).
To do so for an image in the SOUTHERN
HEMISPHERE:
- do the same, but after selecting the appropriate zone, click
the Modify... button and change the false Northing to 0.00.
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