How to correct DRG colors?

04-22-2011 02:32 PM
New Contributor II
I have a DRG in which, for instance, the water features are black instead of light blue.  I've had this happen before, and in my (long ago) notes and it indicated something about repeatedly using Add Colormap until it worked.  Unfortunately that doesn't seem to be the case here -- it is an RGB dataset, which doesn't have a colormap.  The original image is a .jp2, my modified (clipped) version is a .img -- the same problem exists with both.

Attached is a graphic of my DRG.  Any ideas of how to fix?
0 Kudos
1 Reply
Regular Contributor III
Most of the drgs I work with have a 255 color symbology so I can only suggest some options.

First, if you have an rgb drg that displays properly, can you use the import symbolgy from it to fix the one that is displaying improperly?  If that works save the "fixed" drg as a layer file for future use.

Second, if that doesn't work can you use the display background value or no data value as no color to at least get rid of the black?  If so maybe you can see if displaying it as blue might work although that may affect too many areas?

Third, if that doesn't work can you get a hold of Photoshop (I don't know if PhotoElements works) and convert it to an indexed color raster there and then manually symbolize?

Fourth, and what I would first try to do, is download a drg from the state GIS site which usually the 255 indexed color (only 12 are used in most cases).  If not you can an rgb but good looking one from US DataGateway for your county.  You can even use the topo from ArcGIS Online.
0 Kudos