GSDA:Digital Elevation

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Topography and Terrain

WMS-Accessible DEMs


Obtain DEMs directly from WMS using the Get Data tools

WMS offers options to download various types of digital elevation data for anywhere in the world using the Get Data Toolbar. Use either the Get Data From Map button to select an area and download data for the selected area or the Get Data tool to get data for a selected area in the WMS window. This is the recommended method to get DEM data into WMS unless you have other DEM sources that may be more recent or of better quality.

United States Interagency Elevation Inventory

Find US DEMs and bathymetry download sites

The United States Interagency Elevation Inventory is a great source of high-resolution elevation and bathymetry information. If you need higher resolution elevation data, LIDAR data, or bathymetry data that cannot be downloaded directly from WMS, use this web site to locate your area of interest and find data for that area.

USGS Seamless Map

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Obtain Data from USGS National Map Viewer Application

The USGS provides DEM, imagery, land use, hydrography, and other datasets as part of the National Map. The types of data provided as part of this system include:

Shuttle Radar Topography Mission

30 Meter – Data available for contiguous US, Hawaii and southern Alaska
90 Meter *ndash; Extensive coverage including most areas of Earth

National Elevation Dataset (NED)

1/9 Arc Second – 3 meter resolution limited to select areas of the United States
1/3 Arc Second – 10 meter res. available covering most of the contiguous US
1 Arc Second – 30 meter res. for all of the United States
2 Arc Second – Dataset specific for the state of Alaska

Details:

SRTM and NED data is offered in Gridfloat, ArcGRID, and TIFF formats.
You can define a custom, seamless area to download.
The interface allows you to display various GIS layers to aid in the selection process.
Downloads are free (no cost).

USGS Earth Explorer

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Download various data (including elevation) from the USGS


Details:

Download DEM data in various formats.
Download various land cover and vegetation data.
Download USGS imagery.
Downloads are free, but an account must be created to download.

NASA LP DAAC (Land Processes Distributed Active Archive Center)


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Download various data collected by NASA


Details:

Download DEM data from various sources and in various formats from around the world.
Downloads are free, but an account must be created to download.

webGIS


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DEM Data from webGIS

Details:

Terrain data offered
USGS 7.5 minutes - 1:24K scale (~30 m res) <Covers all of contiguous United States>
USGS 1 degree - 1:250K scale (~90 m res) <Hawaii and Alaska only>
Data only available in *.dem format
Graphical US map makes locating an area easy
Downloads are free (no cost).

GeoBase

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Canadian DEM Data

CGIAR-CSI SRTM 90m DEMs (Worldwide)

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Worldwide DEM data in SRTM format-90 meter resolution

MapMart

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SDTS DEM data from MapMart

Details:

Terrain data offered

10 Meter SDTS (Spatial Data Transfer Standard) <Limited coverage of US>
30 Meter SDTS <Covers all of contiguous United States and Hawaii>

Limit of 10 quads per download
Graphical US map makes locating an area easy
Downloads are free (no cost).
The following types of formats are also available for a fee

USGS DEM
XVY ASCII Grid
Arc ASCII Grid
DXF Mesh

GIS Data Depot

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SDTS DEM Data from GIS Data Depot

Details:

Digital Elevation Model (DEM) data:

10 Meter Resolution
30 Meter Resolution

SDTS Format
Extensive coverage of the U.S.
Free downloads.
Data offered free may also be available in other formats for a fee.

Tips:

The USGS GNIS and Google Maps are useful tools to determine the name of the DEM you need.

Land Info

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DEM Data from Land Info

Details:

Digital Elevation Model (DEM) data:

  • 1:250K Resolution
  • 1:24K Resolution

Numerous formats

  • *.dem
  • ESRI GRID
  • ESRI BIL w/HDR
  • *.dted

Downloads must be purchased

Bathymetric

GEODAS Design-a-Grid

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Obtain bathymetry data using GEODAS Design-a-Grid

The National Oceanic and Atmospheric Administration (NOAA) has produced the National Geophysical Data Center (NGDC) website to allow for US data access. Oceanic bathymetry can be found using GEODAS (GEOphysical DAta System) Grid Translator Design-a-Grid.

Details:

  • Must indicate latitude and longitude degree boundaries
  • Three format choices all available with headers:
  1. Binary Raster
  2. ASCII Raster
  3. XYZ Delimited
  • Downloads are free (no cost).


NOAA's National Ocean Service

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Obtain estuarine bathymetry data from NOAA's NOS

The National Oceanic and Atmospheric Association (NOAA) has produced the National Ocean Service (NOS) Estuarine Bathymetry website to allow for US estuarine bathymetry access.

Details:

  • Estuaries divided into six regions:
  1. North Atlantic
  2. Middle Atlantic
  3. South Atlantic
  4. East Coast Gulf of Mexico
  5. West Coast Gulf of Mexico
  6. Pacific Coast
  • 4 downloadable options of individual estuaries in *.dem format:
  1. 1 Arc Second (30 meter resolution) – Split into 7.5" quads
  2. 1 Arc Second – One big file
  3. 3 Arc Seconds (90 meter resolution) – Split into 1 degree quads
  4. 3 Arc Seconds – One big file
  • Downloads are free (no cost).


Topographic and Bathymetric Data Inventory


Obtain topographic and bathymetric data from the Topographic and Bathymetric Data Inventory

The National Oceanic and Atmospheric Association (NOAA) offers topographic and bathymetric data from the NOAA coastal Services Center and the Federal emergency Management Agency through the Topographic and Bathymetric Data Inventory. This resource provides both topographic and bathymetric data for the coastal areas of the United States. More information on this resource can be found here.

DEM Overview

Uses of DEM Data

There are many uses and applications of DEMs. GIS (Geographic Information System) software such as ArcView and ARC/INFO, as well as modeling software such as WMS (Watershed Modeling System) can use DEMs for many engineering and scientific applications. WMS uses DEM data to produce watersheds which are then used to model storm events, create hydrographs, route floods down rivers and through reservoirs, etc. This information can be used to design culverts, dams, detention basins and other hydraulic structures. DEM data are commonly used to create another type of digital terrain model called a TIN (Triangulated Irregular Network). Public domain software is available for tasks such as simply viewing a DEM—one example is dlgv32 Pro, a tool provided by the USGS.

With powerful modeling software such as WMS, using DEM data to run a model is not difficult, and can be accomplished in four general steps:

  1. Find and/or download the needed DEM data.
  2. Import the DEM(s) into WMS
  3. Delineate the watershed by inserting stream networks, one or more outlets, and reservoirs. If desired, a TIN can be created as well. Additional hydrologic data such as land use and soil type can also be used in WMS.
  4. Run the model and view the results. WMS supports several models such as HEC-1, NFF, Rational, TR-55, TR-20, HEC-HMS, and GSSHA.


DEM Definition

A DEM (Digital Elevation Model) is simply a digital map of elevation data. These maps, a type of DTM (Digital Terrain Model), are raster data meaning that they are made up of equally sized gridded cells each with a unique elevation.

DEMs come in different scales and resolutions. For example, 1:24,000 scale DEM is simply a USGS (United States Geological Survey) 7.5’ quadrangle that has been digitized and each cell in the DEM represents a block of terrain 30 meters x 30 meters. The 1:250,000 scale DEM (also known as a 1-degree or a 3 arc-second DEM) has a resolution of 90 meters x 90 meters. DEMs with better resolution are available, but require large amounts of computer memory and disk space and are often impractical to use for large areas of land. If an individual DEM does not cover the entire area of interest, then multiple DEMs can be tiled together to make one large DEM.

The projection and datum for a DEM varies. A common projection for DEMs is UTM (Universal Transverse Mercator) coordinates (meters) and have a specific datum associated with them. Elevations are usually in meters, but sometimes are in feet for areas of low relief, and are referenced to mean sea level.

DEM Tips

Bathymetry Tips