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Narrator:  Since the beginning of time, the Earth's surface has shaped human life. The effects of elevation are essential to where and how we live, the risks of living where we do and the impact we have on the local environment. Digital elevation data helps us interpret and analyze physical features of the landscape for scientific studies. It allows us to see the surface of the Earth in threedimensional views.

Jim Mauck:  Elevation data has been an important component of the US Geological Survey's topographic maps since the 1880's. A topographic map without elevations in the form of contours is simply not a topographic map. Digital elevation models, or DEMs, are collected into a single, multiresolution dataset known as the National Elevation Dataset. As the elevation source for The National Map, the NED provides uptodate bare earth data that describes the Earth's relief.

Narrator:  LIDAR is the NEDs primary source of new elevation data. It's cost efficient, more accurate, and it captures data points from the Earth's surface to the tops of the features above and in between.

Jim:  Its use goes beyond topographic mapping into other areas of science and into everyday life.

David Maune:  FEMA produces flood insurance rate maps that let homeowners know what their risks are of flooding, and LIDAR is essential in making accurate flood maps. FEMA uses hydrologic modeling and hydraulic modeling for their flood studies. The credibility of the National Flood Insurance Program is largely based on the credibility of the elevation data used to produce those flood studies. FEMA computes the water surface elevations for a standard flood event such as a 50year flood, a 100year flood, a 500year flood. What the homeowner wants to know is, what is their risk of flooding? How the special flood hazard area changes depending on whether or not you used accurate LIDAR data in that flood study.

New flood studies done with more accurate LIDAR data tells more people they need to buy flood insurance or in some cases fewer people need to buy flood insurance. LIDAR is the basis for making flood maps accurate.

Karen Schuckman:  In the fall of 1999, Hurricane Floyd hit North Carolina. It was one of the most damaging storms in recorded history. Particularly flooding caused most of the damage. At that time LIDAR was just emerging as a potential technology for collecting accurate elevation data very quickly. One important lesson learned from the North Carolina project was there were many, many other potential users of the data. To find a way to archive, store, distribute, make all that data available in an efficient way really challenged the existing infrastructure, and that's where the USGS really had an important role to play because of their experience with managing large amounts of data over large areas and distributing it to the public.

Mike Renslow:  One thing about LIDAR that's also amazing is everything is in the right place, you know. It's in its true location natively. So it's 3D and it's in the right place. With this it totally revolutionized the way that we measure forest lands because now we have a tool that gives us everything we need. How do we manage this forest? Based on the density of certain kinds of vegetation, how do we best manage it for certain kinds of wildlife habitat or an endangered bird species habitat? When we look at where we are today, when we start to consider things like climate change, when we start to think about where the carbon is in the forest, we now have some reliable information that we can actually use to drive the science to determine how do we mitigate these problems.

Jim:  Through support and partnerships, the elevation data available to The National Map continues to grow and improve, but we have a ways to go. A federallyfunded assessment is currently underway to better understand the requirements, costs and benefits across all levels of government and business for elevation data. Beyond helping to lessen the impact of natural catastrophes, new and improved elevation data fosters new scientific uses and applications that eventually filter down to the general population. Fostering the use of this data is the goal of the Elevation Program of The National Map.

Narrator:  Go to to learn more about how to use elevation information or to become a valuable partner. [music]



Title: Elevation


The National Elevation Dataset (NED) is the primary elevation data product produced and distributed by the USGS National 3D Elevation Program (3DEP). The NED provides seamless raster elevation data of the conterminous United States, Alaska, Hawaii, and the island territories. The NED is derived from diverse source data sets that are processed to a specification with a consistent resolution, coordinate system, elevation units, and horizontal and vertical datums. The NED is the logical result of the maturation of the long-standing USGS elevation program, which for many years concentrated on production of topographic map quadrangle-based digital elevation models. The NED serves as the elevation layer of The National Map, and provides basic elevation information for earth science studies and mapping applications in the United States.

The NED is a multi-resolution dataset that is updated bimonthly to integrate newly available, improved elevation source data. NED data are available nationally at grid spacings of 1 arc-second (approximately 30 meters) for the conterminous United States, and at 1/3 and 1/9 arc-seconds (approximately 10 and 3 meters, respectively) for parts of the United States. Quality Level 3 and higher lidar point cloud are also available in the public domain for download when they are the source of new NED DEMs. Most of the NED for Alaska is available at 2-arc-second (about 60 meters) grid spacing, where only lower resolution source data exist. Part of Alaska is available at the 1/3-arc-second resolution, and plans are in development for a significant upgrade in elevation data coverage of the State over the next 5 years. Specifications for the NED include the following:

  • Coordinate system: Geographic (decimal degrees of latitude and longitude),
  • Horizontal datum: North American Datum of 1983 (NAD 83),
  • Vertical datum: North American Vertical Datum of 1988 (NAVD 88) over the conterminous United States and varies in other areas, and
  • Elevation units: Decimal meters.

Location: USA

Date Taken: 5/1/2012

Length: 5:20

Video Producer: James Maxwell , U.S. Geological Survey

Note: This video has been released into the public domain by the U.S. Geological Survey for use in its entirety. Some videos may contain pieces of copyrighted material. If you wish to use a portion of the video for any purpose, other than for resharing/reposting the video in its entirety, please contact the Video Producer/Videographer listed with this video. Please refer to the USGS Copyright section for how to credit this video.

Additional Video Credits:

Flip Flop Productions

Jim Mauck
Carl Zulick
Mark Newell
Jeff Dietterle
Don Becker
Benedict Kelley

U.S. Geological Survey (USGS),
Earth Resources Observation and Science (EROS) Center,
Science and Applications Branch,
Topographic Science,

National Elevation Dataset (NED) Specialists: Sue Greenlee
Karl Heidemann
Jason Stoker
Gayla Evans
Sandra Poppenga

David Maune
Karen Schuckman
Mike Renslow

File Details:

Suggest an update to the information/tags?

Tags: Elevation NED NGP NationalElevationDataset TNM TheNationalMap USGS


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