3DEP: How the USGS Is Mapping the United States in 3D

A 3D map of St. Louis, Missouri, made from lidar. USGS.

Games and phone apps let you explore imagined virtual worlds. But how do scientists model the real world in 3D?

The 3D Elevation Program

The U.S. Geological Survey, with many partner agencies, runs the 3D Elevation Program — 3DEP, pronounced "three-dep" — to map the United States in three dimensions.

• Lidar: from an airplane, hundreds of thousands of laser pulses a second are fired at the ground. They bounce off buildings, trees, rocks and even the ground beneath the trees. Timing each return gives the distance, and a very accurate virtual map. Lidar — light detection and ranging — is used all over the country.
• IfSAR in Alaska: there the USGS uses interferometric synthetic aperture radar, which bounces radar signals instead of light. Radar sees through clouds, so though less detailed than lidar, it can map very cloudy places.

An airborne lidar system: laser pulses measure the distance from the plane to the surface and back, while GPS tracks the plane. USGS.

From laser to map

Computers turn the returns into 3D models that can become paper maps, 3D computer views, or even apps and games. The goal: 3D data for every inch of the country, so anyone can zoom in on a map and see their neighborhood in 3D.

A 3D lidar map with features labeled. USGS.

What 3D maps are for

New uses keep turning up. 3D maps help:

• predict where floods will reach;
• choose sites for new power plants;
• understand forests and soils;
• grow crops with fewer chemicals;
• find where landslides may happen;
• keep airplanes safely clear of mountains and other obstacles.

Learn more at nationalmap.gov/3DEP.

Sources

Based on 3D Elevation Program—Virtual USA in 3D, USGS Fact Sheet 2016–3022, U.S. Geological Survey (DOI); a work of the United States government in the public domain. The pictures come from the fact sheet's PDF.