Click the checkbox for the "Custom Shading" overlay layer and a text area will appear. Use this to enter condition-color combinations, one per line. The conditions can be any range of slope, aspect or elevation; the color is an RGB hex code. This is best explained with some examples:
|Slopes between 15 and 30 degrees shaded red, as per the first line|
The first line will cause all slopes between 15 and 30 degrees to be colored red (#FF0000). The second shades all slopes between 30 and 45 degrees, with aspects between 90 and 270, blue (#0000FF). If you're not familiar with this notation, search for "hex color codes" or play with the W3Schools color picker. You can also use elevation in meters, or append the number with an f for feet
e1000-2000 matches all elevations between 1000 and 2000 meters.
e5000-7000f matches all elevations between 5000 and 7000 feet.
Each line can match one range each of elevation, slope and aspect, represented by the letter e, a or s and followed by start and end numbers separated by a hyphen. So e7000f-30000fs32-90a225-45 would match all north facing slopes greater than 7000' and 32 degrees or steeper.
|North facing slopes above 7k and 32 degrees or steeper|
If you have only one condition, you can specify a pair of colors to create a gradient. The following creates two gradients: elevations between 5k and 7k are shaded white->blue, and elevations between 7k and 9k are shaded blue->red.
|Mountains around Squaw Valley, CA shaded using the above gradients|
You can also use the service to create nationwide visualizations. And custom layers will also print using CalTopo's PDF generator as well!
|A high level view of terrain 25 degrees and steeper in the Pacific Northwest.|