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This sample uses the TatukGIS Internet Server
LITE to internet publish raster imagery and vector street map coverage's of the
Washington D.C. metropolitan area, including substantial areas of neighboring Virginia
and Maryland. The raster layer was created from fifteen standard (uncompressed, already
rectified and georeferenced) U.S. Geological Survey DOQQ tiff format aerial images
and two non georeferenced black and white tiff aerial photos of the east Washington D.C. area (recent
DOQQ's where not available for this area) also obtained from the USGS, which together
total approximately 2.4 Gb. The TatukGIS AIC product
was used to mosaic/convert/compress the seventeen tiff images into the single 398
Mb georeferenced TatukGIS PixelStore format image published in this sample. The Universal Transverse
Mercator projection of the original DOQQ images was left unchanged, and the AIC was
used to rectify and project the two black and white aerial photos to UTM.
This sample demonstrates the efficiency of the TatukGIS PixelStore format
in handling very large raster imagery files, regardless of image file size. With this
sample, the average user query/map refresh time is approximately one second over a
LAN (depending on the size of the map window displayed in the browser). The user response
speed over a network would be similar even if the pixel image were larger by a factor
of 5, or even a factor of 50 or more, and faster yet if the PixelStore image were
running on a desktop PC application.
The vector layer reflects standard, unprojected, TIGER format street/road map data,
as is provided for free by the U.S. Census Department. The TIGER data was converted
into the faster shp vector format with the use of the free TatukGIS DK viewer sample*. The TatukGIS
Developer Kernel was used to project the vector coverage to the Universal Transverse
Mercator projection, in order to match the raster imagery layer.
It can be seen that the TIGER vector data is not perfectly accurate, with the positions
of streets sometimes tens of meters from true accuracy. Correction of such
inaccuracies to better fit the vector data to the rectified aerial imagery is outside
the scope of this sample.
Clic here to see the source code for this sample.
* The TatukGIS viewer sample is provided as a free DK compiled sample in the DK Sample #3 download package from the TatukGIS web site.
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