Wednesday, April 27, 2005

Category vs. Non-Category Raster

GTViewer and GTVx support a variety of raster configurations. These different configurations are determined by your needs, you raster file type, and your intended uses. This post will try to clarify the differences between the configurations and will hopefully provide enough information to allow you to determine which type of raster is best for you.

GTViewer divides data up in to Categories. The structure of your original data usually determines how Categories are laid out for GTViewer; however, there are no hard-and-fast rules as to how this is done. Categories have their own display controls (display status, min threshold, max threshold). All of the raster formats supported by GTViewer and GTVx can be used in a Category configuration meaning that you can create a Category for one or more raster files. When this Raster category is turned on, the raster files are displayed and the display thresholds defined for the category will automatically turn all of the raster files on or off according to the zoom level. Raster Catgories can support all GTViewer supported raster formats (ECW, MrSID, CIT, RLE).

GTViewer and GTVx also support a Non-Category Raster configuration where a list of raster files (ECW or MrSID) is supplied along with an independent display status and threshold for each file. The Raster Display Filter Dialog allows the user to independently control the display of each Non-Category Raster file.

Pocket GTViewer has limited raster support, but it does support the ECW file format in a Non-Category Raster configuration. The raster requirements on the Pocket PC or Windows Mobile platforms are generally much different than on the Desktop because of the limited resources of the devices. This configuration seems to work best on devices. Originally, the Non-Category configuration was only for Pocket GTViewer, but its usability was so good that the functionality was also integrated into GTViewer and GTVx.

Raster Summary:

GTViewer and GTVx both support the following Raster Configurations:
  • ER Mapper’s ECW raster format in Category and Non-Category configurations
  • Lizard Tech’s MrSID raster format in Category and Non-Category configurations
  • Intergraph CIT Binary raster format in Category configurationsIntergraph RLE Binary raster format in Category Configurations

Pocket GTViewer supports the following Raster Configurations:

  • ER Mapper’s ECW raster format in Non-Category configurations.

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