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Tiling Scheme
All raster data stored in the
King County Spatial Data Warehouse (KCSDW) image library is structured into a standard
set of tile schemes integrated with a complementary naming convention. Tiling allows the large raster datasets to be
‘broken-up’ into manageable file-size pieces for use in GIS and other viewing
software.
Idxptrmbr –
township/range-based tile scheme
Most users will find that data
tiled according to the “idxptrmbr” tile scheme, based on townships of the Public
Land Survey System (PLSS), will meet the majority of their business needs. This data is
minimally compressed (near lossless) imagery or resampled, but densely-posted grid data.
Idxp7500 – Lowest-level
‘Building block’ tile scheme
This lowest level tiling index is where
the dataset is stored in its highest-resolution “building-block” version.
Generally data at this level is accessed only for detailed, small area projects
or when access to the native data format for imagery is necessary. Imagery at this level
is stored in lossless format and other rasters are stored with maximum detail.
Idxpzone –
Multiple tile mosaic for large project areas
Where your project area involves
multiple townships or where a lower resolution raster or image will suffice, tiles
of the idxpzone index may meet your needs. King County
and an adjacent buffer area is subdivided into 4 ‘quadrants’ – NW, NE, SW, and
SE. Imagery at this level will be compressed, thus reducing its resolution, but
making access more efficient. Likewise, other raster data will be resampled to
reach an effective sample density/file size median.
KeyRegion – Full extent of
dataset
For a given dataset, all tiles of
the data are assembled into a single mosaic/file. The extent of the KeyRegion
file will vary depending on the original extent of the component data. Data
will be of significantly reduced resolution to accommodate file size
limits. However, the single file per dataset is useful for illustrating county-wide areas and as a quick reference
for determining an area of interest.
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Metadata:
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KeyRegion bounds are not really
an index, but will vary depending on the dataset described, thus there is no
metadata for this storage level. See the metadata for the dataset itself for
its extent description and other information.
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Graphic:
For more details
regarding the organization of the image/raster library, see
PlibChgPlibrary3.doc
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