The Gaussian Blur option is available from Editor Menu bar under the "Tools - Gaussian Blur" option.

Gaussian Blur is a method of softening an image that is too sharp. Depending on the mode in which the image was scanned, the details may be too sharp. The image may also be too sharp if it was converted from color to black and white using the Enhancement tools.

You control the intensity of the blur by setting the size of the blur radius. Larger radii give more blurring. Smaller radii give less blurring. For the purpose of editing cave maps, blurs in the range of 0.5 are usually best.

As an example of how the blurring works, the image to the right was was converted to black and white. This causes the subtle variation of color around the edges of the lines to be lost, (although it does quickly remove a lot of extraneous detail). As you can see, the image looks overly sharp and stark.

The next image shows the sketch with about 0.7 Gaussian blur applied. As you can see, the image is softer and more natural looking.