Pitney Bowes MapXtreme - Manual (Page 318)

Chapter 17: Working with Rasters and Grids
Grid Images
MapXtreme v7.1 325 Developer Guide
Use the <SpecialPath> syntax if the application data is stored in a location relative to a .NET
Framework special system folder. For example, if your application data is stored in a directory
named MyAppData located under the “My Documents” directory, then the entry in the configuration
file could be:
<Personal>MyAppData</Personal>
where “Personal” is the value of the .NET Framework enumeration Environment.SpecialFolder that
represents the “My Documents” directory.
This configuration method can also be used to change the preferred raster handler for file types that
can be managed by more than one raster handler. For example, a JPEG file can be handled by
either Halo or LEADTOOLS (both of which are bundled in MapXtreme). Normally, Halo has priority
because its *.rhv file extension alphabetically precedes the LEADTOOLS *.rhx extension. However,
because MapXtreme first looks in any <ApplicationDataPaths> defined in the configuration file, it will
locate a specified raster handler before looking for a handler in the default [CommonFiles] folder. So,
for example, you could copy a LEADTOOLS *.RHX handler in the defined folder and configure
MapXtreme to find and use that handler first.
Alternatively, you can rename file extensions in the [CommonFiles] folder so that the desired raster
handler appears first in the alphabetic list. However, this will affect all applications developed with
MapXtreme and may produce unintended side effects. Also, if file extensions are changed in this
manner, the renamed raster handlers will not be deleted if MapXtreme is uninstalled. For these
reasons, you may want to use the configuration method to change the location and precedence of
raster handlers.
Grid Images
Grid images show an interpolation of data values across an area. A grid image is created from a
data file in which data is measured at evenly-spaced points. The entire map area is converted to a
grid in which each grid cell represents a value. Grid values don't have to be interpolated to produce
a grid, although the data collection points need to be regularly spaced. MapXtreme and MapInfo
Professional create grids by interpolating values using a grid handler.
In addition to the color gradations, grid images can also show hill, or relief, shading. Relief shading
allows the grid surface to be shaded according to a virtual light source. The brightness of each grid
cell corresponds to the light striking the surface and is adjusted based on its orientation to the light
source. This is well suited for elevation grid maps where you can take surface slope and direction
into account relative to the direction of the light. Maximum brightness is assigned at points where the
sun’s rays are perpendicular to the surface. As the slope faces turn away from the light source, the
brightness values are lower.
Supported grid formats include:
• MapInfo Grid (*.mig)
• USGS DEM (*.dem)
• GTOPO30 (*.dem)
• DTED (*.dt0, *.dt1, *.dt2)