Shaded Relief

There are two shaded relief services: (1) USGSShadedReliefOnly (MapServer), which is a tile cache base map service from world scale to 18K, and (2)
Small-scale shaded relief layers (30 arc-seconds and larger cell sizes) are derived from the USGS GTOPO30 dataset.
Coverage consists of the contiguous United States, Alaska, Hawaii, Puerto Rico, the Virgin Islands, Guam, Palau, American Samoa, the Federated States of Micronesia, the Marshall Islands, the Northern Mariana Islands, and the country of Mexico.
The shaded relief simulates point illumination from the northwest with the light source 45 degrees above the horizon. A small amount of vertical exaggeration is applied. Contrast adjustments and tinting were chosen for cartographic effect.
Shaded relief layers based on GTOPO30 are represented in 30, 60, and 120 arc-second cells. The approximate equivalent metric values are 1, 2, and 4 kilometers.