Follow

Removing the Map Collar from a DRG File in Didger 3 and Exporting as a GeoTIFF without Losing Resolution

One of the many features of Didger 3 is the ability to automatically remove the map collar from a USGS Digital Raster Graphic (DRG) file. DRG files are scanned topographic maps that typically have collars. The map collar is the area around the map that contains information such as projection, quadrangle location, latitude/longitude and UTM tick marks, map scale, etc.

Removing the collar from a DRG with an FGD file is simple. However, Didger will always export georeferenced image files from a vector project at a resolution of 300 dots per inch (DPI). Based on the physical size of the vector project, this may result in an exported image that contains significantly fewer pixels than the original image, resulting in a loss of image quality. To export a higher number of pixels and increase the resolution, you must go to View | Project Limits and increase the size (length) of the project. Once the project is larger, you can export it to a GeoTIFF and you will retain more pixels and therefore better resolution.

To retain the original resolution of the image, the key is to determine what exactly to enter for the length values. To do that, you can follow the steps outlined in the attached newsletter article: Removing the Map Collar from a DRG File in Didger 3 and Exporting as a GeoTIFF without Losing Resolution.pdf.

Updated October 19, 2016

Was this article helpful?
0 out of 0 found this helpful
Have more questions? Submit a request

0 Comments

Please sign in to leave a comment.