rfSoftware products currently use 3 different terrain databases: 30-second data from the FCC, 30-second data from the GLOBE (Global Land One-km Base Elevation) project and 3-second data from the USGS. Below is a sample of each from the Boston/Cape Cod area shown at 1:1,000,000 scale.

30-second FCC: The primary limiting factor in this data is its 10-meter vertical resolution. Notice that much of the low-lying terrain registers as 0 meters elevation.

30-second GLOBE: The GLOBE data has 1 meter vertical resolution. Notice the greater degree of variation compared to the FCC data.

3-second USGS: 3-second terrain data is 100 times denser (10 times in each direction) than the 30-second data. Until you zoom in to 1:250,000, the data resolution is higher than screen resolution.