NGP Standards and Specifications

3D Elevation Program Standards and Specifications

The National Map serves elevation data for the United States at a variety of resolutions. The most recent and highest resolution elevation data are acquired by the USGS 3D Elevation Program. The primary goal of 3DEP is to systematically collect 3D elevation data in the form of light detection and ranging (lidar) data over the conterminous United States, Hawaii, and the U.S. territories and interferometric synthetic aperture radar (IfSAR) in Alaska.

Lidar Base Specification

The Lidar Base Specification (LBS) addresses the need for interoperable data across collections with a goal towards a nationally consistent dataset. As such, the LBS is the source of requirements for collections under the 3D Elevation Program (3DEP). The latest version of the LBS, v. 1.3, was released February 28, 2018.

Elevation Specifications Review Board

Updates to the 3DEP Lidar Base Specifications are managed by the Elevation Specifications Review Board (ESRB). Advancements in technology often outpace updates to specifications and requirements. The ESRB was formed to keep pace with technological advancements. Requests for modifications and additions to existing specifications are presented to the ESRB for review. ESRB approved requests are then presented to the 3DEP Working Group for final approval. Approved changes are published through the Specifications Explorer Database (Spec-X).

Data on America’s elevation have typically been represented as contour lines and bare earth digital elevation models (DEMs) in The National Map. Light detection and ranging (lidar) and interferometric synthetic aperture radar (ifsar) data (in Alaska) are now the primary sources of elevation data for 3DEP, and provide opportunities for measuring, mapping and monitoring not only the bare earth surface, but above ground features as well. As a result, in addition to the traditional bare earth DEMs, USGS now provides the source lidar point clouds, ifsar digital surface models (DSMs) and orthorectified radar intensity images (ORIs) over every area where data have been acquired for 3DEP and The National Map. Contours derived from these elevation data are used in the US Topo digital topographic maps. 

Three bare earth DEM layers in 3DEP are nationally seamless and are distributed in geographic coordinates at 1/3, 1, and 2 arc-seconds. Two high resolution layers over the conterminous U.S., 1/9 arc-second and 1-meter, are seamless within projects but not across projects. The 1-meter bare earth DEM dataset will be populated as new data are acquired. The quality and accuracy of these datasets are governed by standards and specifications.