Today I would like to show a way to quickly create a pseudo-3D display from this map:
Original image
The map is a screen capture of a meandering river near Galena, Alaska, taken in Google Earth. I love this image; it is one of my favorite maps for several reasons. First of all it is just plainly and simply a stunningly beautiful image. Secondly, and more practically, the meanders look not too dissimilar to what they would appear on a 3D seismic time slice displayed in grayscale density which is great because it is difficult to get good 3D seismic examples to work with. Finally, this is a good test image from the filtering standpoint as it has a number of linear and curved features of different sizes, scales, and orientation.The method I will use to enhance the display is the shift and subtract operation illustrated in The Scientist and Engineer’s Guide to Digital Signal Processing along with other 3×3 edge modification methods. The idea is quite simple, and yet extremely effective – we convolve the input image with a filter like this one:
0 0 0 0 1 0 0 0 -1