For decades, engineers have relied on a patchwork of data—field surveys, orthophotos and other sources—to piece together baseline topographic information for infrastructure design and related work. The U.S. Geological Survey (USGS) has long recognized that consistent 3D elevation data for the entire United States would bring major economic and practical value to local, state and federal initiatives. Now, in 2026, after roughly eight years of targeted collection through state and local partnerships, the nation is nearing completion of its first consistent national baseline of high-resolution 3D elevation data.

USGS’ 3D Elevation Program (3DEP), which provides high-resolution Light Detection and Ranging (LiDAR) data for the contiguous United States, Hawaii and U.S. territories, as well as Interferometric Synthetic Aperture Radar (IfSAR) data for Alaska, gives planners and engineers a consistent elevation foundation for performing their infrastructure design work.

USGS has called 3DEP a “digital twin of the nation’s topography,” and that’s a fair description. Decision-making in stormwater hydrology, flood studies, transportation planning and infrastructure-related fields becomes more accurate because 3DEP captures surface detail at high resolution. As a critical input for engineering projects, 3DEP offers strong practical value by reducing uncertainty and allowing engineers to sharpen and refine their designs and analyses. Despite the limitations of any dataset—and 3DEP is no exception—these data will remain an invaluable source of technical clarity for years to come.

Advantages and Applications

It’s hard to overstate the importance of LiDAR data, which are used increasingly in fields as diverse as civil engineering, urban planning, precision agriculture and hazard mitigation. LiDAR works by tracking sensor-emitted light pulses that reach Earth’s surface and return, generating millions of elevation points in what’s referred to as a “point cloud.” These points represent terrain in all its variability: tree canopy, buildings, bare land and other surface features. Digital elevation models (DEMs) can be derived from LiDAR data and represent “bare earth,” stripped of surface features in a data-dense topographic profile. Ultimately, 3DEP reduces inconsistencies in engineering analyses caused by outdated maps, land surveys collected in different years and other uneven source data. As future collection cycles are completed, the 3DEP dataset will become a more complete record with each iteration, tracking how the natural and built landscape—and specific projects—change through time.

The use of LiDAR in water-resources management is growing. Floodplain mapping and watershed delineation, HEC-RAS 2D model development, stormwater design plans, and dam failure and other analyses become more defensible because they can be based on a consistent elevation framework. The 3DEP dataset provides a baseline from which to compare different civil engineering designs or stormwater management strategies. Subtle changes in terrain and slope can be detected, making greater accuracy in drainage design achievable. Moreover, these data can be readily integrated with hydrography, vegetative cover and related datasets. For example, in one recent study by Oladunjoye et al., LiDAR was used in combination with multispectral sensing to track and assess the long-term performance of stormwater management practices through time.

3D Elevation Data in Practice

From a hydrologist’s perspective, one of the principal advantages of 3DEP is the ability to do preliminary terrain processing without the need to send out a field crew for early stage survey work. In a hypothetical case of reconstructing a circa 1950s dam, for example, 3DEP DEMs could be used to delineate watershed geometry and upstream subbasins; and identify flow paths, slope, basic surface contours and more for purposes of building a preliminary terrain model. Similarly, 2D flood surfaces downstream of the structure may be plotted for downstream flow in the event of a dam breach. Important details showing subtle terrain variability—often indiscernible in coarser elevation data—can be identified before design flaws affect model accuracy and performance.

USGS is still in the process of integrating 3D hydrography data, but supplementary data for channel bathymetry, storage curves, dead storage and other hydrologic details would remain necessary. Despite quality controls, error can be introduced where LiDAR penetration may be compromised, as in areas of dense vegetation, rocky outcroppings or places where earthworks have recently been modified. Detailed site surveys are needed under these conditions. For example, a project involving dam reconstruction is complex and mandates design-grade accuracy. Supplementary topographic surveys, field-validated measurements, geotechnical information and other structure-specific data are essential, but 3DEP data provide an invaluable baseline of information for further analysis and investigation.

The 3DEP program is only one part of the comprehensive 3D National Topography Model vision launched by USGS. Ultimately, this “digital twin” of the United States will consist not just of 3D elevation data, but important hydrographic data (3DHP) as well. It has been referred to as an integrated “living model” of the United States, and it’s bound to change how we approach many planning decisions. Our profession will be laboring under engineering challenges for years to come, but the quality and scale of the data coming online are keeping pace with the need. Our charge is to continue developing ways to make the best use of them.