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TIFF
data format
Concepts:
TIFF
ArcSDE raster
ArcInfo GRID
The
data provided are either in TIFF format (on the DVD) or as an ArcSDE
raster. TIFF (Tagged Image File Format) files are a universal
data standard which can be used in a wide variety of image processing
and GIS software. ArcSDE rasters are just rasters stored in
ArcSDE (the format Maine state employees will see in ArcGIS).
Both of these formats have some shortcomings when used in ArcGIS.
The biggest is the inability to use a raster attribute table (a.k.a.
value attribute table or VAT). Such a table contains additional
fields aside from just the pixel's numeric value. For example, a
"High-density Developed" pixel in MELCD 2004 will have a numeric value
of 2. But with TIFF and ArcSDE, that's all the user sees, and
must refer to the metadata or some other source to know what "2"
means. An attribute table provides those extra descriptions right
in the raster. This would be especially true for the NLCD 2001
change detection data, since there are 147 different classes.
People working outside Maine state agencies may want to consider
converting the TIFF to an ArcInfo GRID. This is just another
format for use in ESRI software, but it does have the advantage of
using attribute tables for rasters. A text lookup table is
included for landcover data on the DVD.
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