Webinar 55
3D Elevation Program (3DEP) Data for Transportation

March 26, 2025

Summary of the Federal Highway Administration’s Quarterly Webinar

The Federal Highway Administration (FHWA) promotes geographic information systems (GIS) as a means to manage and improve transportation systems more effectively. One of the ways that FHWA does this is through its GIS in Transportation program,¹ which identifies timely and critical GIS issues and topics in transportation and connects transportation agencies with available resources and best practices. The webinar summarized here is part of a quarterly series organized through the GIS in Transportation program.

The 3D Elevation Program (3DEP), managed by the United States Geological Survey (USGS) National Geospatial Program, responds to growing needs for high-quality topographic data and for a wide range of other three-dimensional (3D) representations of the Nation’s natural and constructed features. The webinar provides an overview of 3DEP data and three example use cases in transportation. Presenters are Jason Stoker, US Geological Survey (USGS), Dr. David Maidment, University of Texas, Austin, Jeremy L. Penton, Louisiana Department of Transportation and Development (LADOTD), and Matt Lauffer, North Carolina Department of Transportation.

Jason Stoker presented an overview of the 3D Elevation Program which provides high-quality topographic data and 3D representations of the nation’s natural and constructed features. Light Detection and Ranging (Lidar) data is used and this data replaces the previous National Elevation Dataset (NED). 98.3% of the nation now has 3DEP data available or in process.

Dr. David Maidment, a hydrologist, presented on road and bridge elevation models using 3DEP data to support assessment of flood impact on roads and bridges. Also used in the modeling are the National Oceanic and Atmospheric Administration’s (NOAA) National Water Model, which continually forecasts flow on 2.7 million stream reaches, and the National Water Predication Service, which provides river stage observations, forecasts and long range flood outlooks. The National Weather Service combined these data sets to get a relative elevation map of the nation which is used in modeling. Dr. Maidment demonstrated the use for specific road and bridge cases.

Matt Laufer, the State Hydraulics Engineer, presented on the use of water data in the North Carolina Department of Transportation (NCDOT). This includes discussing LiDAR in resilient Planning, hydraulic modeling and design, and NCDOT’s flood warning tools. Some uses of the Lidar data are discussed with real world examples, include for hydraulics and hydrology digital elevation models, such as for coastal change and flooding, for the structural health monitoring and restoration activities of bridges, and for resilience planning related to hurricanes.

Jeremy Penton, LADOTD, presented via a Story Map which gives an update to the Louisiana’s statewide topography mapping program. He discussed major program activities, milestones and achievements since 2017 related to their LiDAR data collection. He also discussed details of their LiDAR data collection process, some different uses of the data, and over 100 data sets related to the topographic data.

A recording of the webinar is available. Please use passcode w@2*B72j to access it.

Questions & Answers

Questions for Jason Stoker

Do you have any APIs available to access your data?
Yes. It is called TNM Access API. It enables a person to tap into and filter on the datasets.

Is the LiDAR Hillshade in the TNM Advanced Viewer and in https://elevation.nationalmap.gov/arcgis/rest/services/3DEPElevation/ImageServer 1m or 3m?
Yes, the LiDAR hill shade is available in the TNM Advanced Viewer. Other ways to access that is through our Dynamic Elevation Service. Not only are the hill shades available, but also the right slope aspect and other derived things that get rendered on the fly. We have a training video. The Dynamic Elevation Service is multi-resolution, from the scale of the entire United States, to drilling down to different pyramids of resolution to the one meter data level.

Our 3DEP subcommittee provides advice. Do you have other committees that provide advice to the 3DEP Program?
Yes, we have a 3DEP working group, and a 3DEP Federal Interagency Coordination Committee, which is more of an executive level that provides recommendations.

How is the 3DEP Program preparing for the 2022 datum change?
We’ve been following that for several years. When it becomes official, we will just require the new NSRS in contracts. We’re discussing and debating right now do we reprocess or reproject all existing data into those data frames, or what data layers do we do it for, because it will be an expensive and massive effort. We hope to have recommendations by the end of this fiscal year.

If a government agency, such as a state DOT, has in-house data collection, will the 3DEP Program accept that data?

1. If the data meets our 3DEP specifications we would love to discuss it being contributed, or connected through something we are working on called the 3D Nation Ecosystem—happy to discuss. I would say the DOT and the taxpayer would benefit by providing pre access to this data.
2. This link should get you what you need: https://www.usgs.gov/news/technical-announcement/new-elevation-map-service-available-usgs-3d-elevation-program.

Questions for Dr. David Maidment

What do you think prevents state agencies that are not using a lot of elevation data from using this data? What is the roadblock?
This data is very heavy and you have to be able to work out a methodology for isolating the LiDAR that are relevant for the transportation purpose from all the rest. We’ve done this in Texas; we have about 70 data collections. In the exercise of pouring the data onto the road network, we constructed a map of space and time data. Then we selected form that the most recent points everywhere they exist. That is a complicated undertaking and you need high performance computing. We worked with the Oak Ridge National Lab.

Do you have recommendations how to encourage those state agencies that are not utilizing 3DEP LiDAR data to do so?
We have a wide range of applications and have found partners to make use of the data. We are happy to share our experience.

When data collection is near the state line, are there efforts to partner with adjoining states to collect that data to be more efficient?
Dr. Maidment is not involved with data collection in Texas.
Gary Thompson answer: In North Caroline we do talk with our partners in adjoining states to make them aware of the data collection. If there is any joint data collection, we will coordinate with them.

Question for Matt Laufer

Is the LiDAR data you are collecting documented and has the date published?
The county side LiDAR data that we are collecting has metadate with the date of collection and when it is published. This will be similar with the UAV data.

Questions for Jeremy Penton

Is your Story Map public facing?
No, it is not public facing right now.

Have you been contacted by neighboring states about flying their coastlines for QL1 LiDAR?
There were some talks with Texas, but I’m not 100% sure.

Do States collect data in house or do they use contractors?
LADOTD has done small portions of the state in-house but mostly uses contractors. Texas also contracts everything out. There is on in-house mapping with the state agencies. North Carolina also uses contractors.

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