GRD, Northwood .GRC, .GRD

GRD files provide data in Northwood / Vertical Mapper grid format and usually provide projection information so the resulting raster image is georegistered.   Manifold can read several different types of .grd formats and will automatically configure for Northwood style .grd when a Northwood GRD is chosen.



To import from GRD format:


  1. Choose File-Import from the main menu.

  2. In the Import dialog browse to the folder containing data of interest.

  3. Double-click the file ending in .grd for the data of interest.

  4. A table and an image will be created.




We can double-click on images that are created to view them.   For a more interesting display, we first create a new data source using a Bing street maps image server as shown in the Example: An Imageserver Tutorial topic.   We then create a map and drag and drop the Bing layer into the map, and then we drag and drop the image into the map.



The image appears using the correct projection, but it is dark, and it has a "collar" of black pixels around the data area.   We must use the Style  pane to assign a palette to color the elevation values in the image.



We use the Style pane to color the image using a palette. The use of transparent color for the first interval is a quick and dirty hack, to get rid of the collar.



That provides a more sensible display.  In the illustration above, we have added a transparent streets Google image server layer above the california_zone11 image, to provide better context.  The display shows terrain elevation values in Los Angeles.    



Getting rid of the collar - A more skilled way to get rid of the collar would be to select a tile containing the collar, to see what number coded the black region.  We could then add an interval just for that color, make that color transparent, and start the next interval with the color range intended for the raster.

See Also











GRD, Surfer .GRD


Example: Spectacular Images and Data from Web Servers


Example: An Imageserver Tutorial