Pitney Bowes MapInfo Professional - Manual (Page 287)

handler formats depend on what grid handlers have been installed. Changing the default grid handler
will change the default file extension of the grid file name.
Grid files are stored by default in the data directory specified as a preference. Grid files can be opened
from the File menu, click Open command like other MapInfo Professional supported file types.
When you open a table that has a grid filename associated with it, MapInfo Professional searches for
the file if it cannot find it immediately. For example, the search capability can simplify opening tables if
your .tab file refers to an image that resides on a DVD drive, and different letters are used to designate
the DVD drive on different systems.
MapInfo Professional uses the following search order:
1. Search for the file where specified by the FILE tag in the .tab file.
2. Search for the file in the same directory as the .tab file.
3. Search for the file in the Table Search path specified in the Directories preferences.
MapInfo Professional either opens the table as though it found the file in the specified location, or it will
report an error because the file could not be found in any location.
Working with Grid Handlers
In addition to the MapInfo Professional read/write grid handler (*.MIG) we also supply READ-ONLY grid
handlers to support the direct opening of the following grid file formats:
• DEM-USGS ASCII(*.DEM)
• DTED-levels 1, 2, and 3 (*.DT0, *.DT1, *.DT2)
• GTOPO30 (*.DEM)
• MapInfo Vertical Mapper (*.GRD, *.GRC)
You can open these grid file types directly from the Open dialog box. You will see the file extensions
listed next to the Grid Image file type in the Files of Type drop-down list in the bottom of the dialog box.
Because the handlers are read-only, they cannot be used to create grid files during the thematic mapping
process.
If the relief shading option is enabled (in the Create Thematic Map - Step 3 of 3 wizard panel, click
Styles and then Grid Appearance), a separate file will be created to store the hill shade information.
The hillshade file is stored in the same location as the grid file and has the same base name as the grid
but with the extension ".MIH". If the grid file is read-only, for example, it's located on a DVD, the .MIH
files will be created in the same location as the .tab file. The .tab file will contain a new metadata key,
for example:
"\Grid\Hillshade File" = "d:\tmp\AntiochSouth.MIH"
Vertical Mapper Grid Handler
MapInfo Professional also includes the Vertical Mapper Grid handler to enable users who have not
purchased the full Vertical Mapper add-on product to open, view, and print Vertical Mapper Grid (*.GRD,
*.GRC) format files.
The Vertical Mapper Grid files can also be opened directly in MapInfo Professional. The *.GRD or *.GRC
extension is listed with the other Grid Image formats in the Files of Type drop-down list.
Currently, grids using the Vertical Mapper handler cannot be modified in the Modify Thematic Map
dialog box. They are read-only. They must be created or modified in the Vertical Mapper source
application, which is available from Pitney Bowes Software Inc.. In addition, you cannot create .GRD or
.GRC files in MapInfo Professional, however, you can convert *.GRD files to *.MIG files with
GRIDTOOLS.MBX.
The Help System contains these related topics:
• Creating Custom Read/Write Grid Handlers
• IDW Interpolator
287 MapInfo Professional User Guide
Chapter 10: Creating Thematic and Other Themed Maps