Autodesk 15606-011408-9320 User Guide - Page 98

Tiled TIFFs, Raster Image Catalog Files

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Tiled TIFFs Because raster images can be quite large, they can slow down performance. To improve performance significantly, use tiled TIFF files. A tiled TIFF file allows Autodesk MapGuide to access only specific portions of the image. This greatly improves access speed, because Autodesk MapGuide Server does not need to load the entire image every time-just the specific portion requested. The difference in performance between using standard TIFF files and tiled TIFF files is dramatic. You can use Autodesk MapGuide Raster Workshop to generate tiled TIFFs from other raster file formats. Raster Image Catalog Files In addition to individual raster image files, Autodesk MapGuide supports raster image catalog (RIC) files. A RIC is a list of raster image files and their lower-left and upper-right coordinates. When creating a raster map layer, you can reference an individual raster image, in any of the supported formats shown on page 97, or in a RIC file. Each raster image file (whether an individual image or a RIC) must be accompanied by a georeferencing file, which provides additional information about how to position the raster image on the map. When you access a layer that references a RIC file, Autodesk MapGuide Server scans through the RIC file to determine the images or portions of images that correspond to the area being viewed, and then sends only the data for that area. This greatly increases performance, as only the necessary data is stored in memory instead of the entire image. It is important to keep in mind that the RIC file only determines which images might be visible. Georeferencing information for each individual raster image must still be available, as this information (not the information in the RIC file) is used to place them in the correct position on the map. Note that the raster image must be based on the same coordinate system as the rest of the data on the map, and it cannot be converted automatically if you change the coordinate system for the map. If Autodesk MapGuide Server is running under the System account, please note the following:  All of the image files in the RIC must be on the same server as the RIC.  The RIC must reference the raster image files using relative paths. If you use a computer name in the path, Windows NT/2000 will not be able to recognize it. 98 | Chapter 5 Working with Data in Autodesk MapGuide

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98
|
Chapter 5
Working with Data in Autodesk MapGuide
Tiled TIFFs
Because raster images can be quite large, they can slow down performance.
To improve performance significantly, use tiled TIFF files. A tiled TIFF file
allows Autodesk MapGuide to access only specific portions of the image. This
greatly improves access speed, because Autodesk MapGuide Server does not
need to load the entire image every time
—
just the specific portion requested.
The difference in performance between using standard TIFF files and tiled
TIFF files is dramatic. You can use Autodesk MapGuide Raster Workshop to
generate tiled TIFFs from other raster file formats.
Raster Image Catalog Files
In addition to individual raster image files, Autodesk MapGuide supports
raster image catalog (RIC) files. A RIC is a list of raster image files and their
lower-left and upper-right coordinates. When creating a raster map layer, you
can reference an individual raster image, in any of the supported formats
shown on page 97, or in a RIC file. Each raster image file (whether an indi-
vidual image or a RIC) must be accompanied by a georeferencing file, which
provides additional information about how to position the raster image on
the map.
When you access a layer that references a RIC file, Autodesk MapGuide Server
scans through the RIC file to determine the images or portions of images that
correspond to the area being viewed, and then sends only the data for that
area. This greatly increases performance, as only the necessary data is stored
in memory instead of the entire image.
It is important to keep in mind that the RIC file only determines which
images might be visible. Georeferencing information for each individual
raster image must still be available, as this information (not the information
in the RIC file) is used to place them in the correct position on the map. Note
that the raster image must be based on the same coordinate system as the rest
of the data on the map, and it cannot be converted automatically if you
change the coordinate system for the map.
If Autodesk MapGuide Server is running under the System account, please
note the following:
All of the image files in the RIC must be on the same server as the RIC.
The RIC must reference the raster image files using relative paths. If you
use a computer name in the path, Windows NT/2000 will not be able to
recognize it.