Office of Geomatics

ArcticDEM

ArcticDEM is a National Geospatial-Intelligence Agency and National Science Foundation (NSF) public-private initiative to automatically produce a high-resolution, high-quality digital surface model (DSM) of the Arctic using optical stereo imagery, high-performance computing and open source photogrammetry software. NGA and NSF partnered with the University of Minnesota and other members of the academic research community, private sector and international partners to create this first-ever publicly available, high-resolution, satellite-based elevation dataset.

ArcticDEM data depicts the reflective surface and includes a collection of time-dependent, 2-meter DEM strips and an 8-meter seamless mosaic that can be distributed without restriction. ArcticDEM data will encompass all land area north of 60° north latitude. In addition, coverage will include all territory of Greenland, the entire state of Alaska, and the Kamchatka Peninsula of the Russian Federation. The producers did not intend the final product to be a single "eyes on" or edited product, but rather a collection of time-dependent elevation models and the infrastructure to process the flow of imagery from an ever-expanding constellation of satellites producing an ever-increasing volume of high-quality data.

More info on the ArcticDEM: https://www.pgc.umn.edu/data/arcticdem
View the ArcticDEM: http://arcticdemexplorer.s3-website-us-west-2.amazonaws.com

REMA

The Reference Elevation Model of Antarctica (REMA) is a National Geospatial-Intelligence Agency and National Science Foundation (NSF) public-private initiative to automatically produce a high-resolution, high-quality digital surface model (DSM) of Antarctica using optical stereo imagery, high-performance computing and open source photogrammetry software. NGA and NSF partnered with the University of Minnesota and other members of the academic research community, private sector and international partners to create this first-ever publicly available, high-resolution, satellite-based elevation dataset.

REMA provides the first, high resolution (8-meter) terrain map of nearly the entire continent. Since each REMA grid point has a timestamp, any past or future point observation of elevation provides a measurement of elevation change. The time-dependent nature of the strip DEM files allows users to perform change detection analysis and to compare observations of topography data acquired in different seasons or years. The mosaic DEM tiles are assembled from multiple strip DEMs with the intention of providing a more consistent and comprehensive product over larger areas, while also providing a time stamp and error estimate for each pixel to enable to change detection. The tile data are registered to satellite altimetry to increase their absolute accuracy while strips are not. Registration data for strips may be provided in later REMA versions.

More info on REMA: https://www.pgc.umn.edu/data/rema
View REMA: https://www.maps.arcgis.com/apps/View/index.html?appid=86a9728459aa4d18b4444b74d330832e

Digital Terrain Elevation Data (DTED)

DTED is a uniform matrix of terrain elevation values and provides basic quantitative data for systems and applications that require terrain elevation, slope, and gross surface roughness information. DTED products are produced at three levels of resolution described below:

• DTED Level 0 corresponds to small scale hardcopy products, and has a post spacing of 30 arc-seconds, or one kilometer nominal resolution.
• DTED Level 1 corresponds to medium scale hardcopy products, and has a post spacing of three arc-seconds, or 100 meter nominal resolution.
• DTED Level 2 corresponds to medium to large scale hardcopy products, and has a post spacing of one arc-second, or 30 meter nominal resolution.

Distribution of DTED and the Digital Data Products catalog is authorized to the Department of Defense, U.S. DOD contractors, and to U.S. Government agencies that support DOD functions (by authority of the Director, National Geospatial-Intelligence Agency, 30 May 1990).

Digital Bathymetry and Elevation Data (DBED)

DBED is a point prediction of global bathymetry and elevation values in meters stored in the format of DBED Level 0. It allows for a gross representation of the Earth's physical surface for general model and assessment activities. DBED is currently based upon the WGS 84 Earth Gravity Model 1996 (EGM 96).

Shuttle Radar Topography Mission (SRTM)

The SRTM mission began in 2000 as a joint venture between NASA and NGA to use a modified radar system onboard the Space Shuttle Endeavour to acquire reflective surface elevation data for over 80 percent of the Earth's land mass. SRTM data is available at two resolutions: 1 arc-second (nominal 30-meter) and 3 arc-seconds (nominal 90-meters). As part of an ongoing commitment to open data and international data sharing, SRTM datasets were released to the public and are currently available through USGS's Earth Explorer website.

TanDEM-X

TanDEM-X data is a reflective surface elevation dataset produced at a ground sample distance of approximately 12 meters. TanDEM-X data may be either raw (TDR) or finished (TDF). The TDR product is the result of a fully automated processing chain and may still contain undesirable artifacts. NGA participates in the TanDEM-X High Resolution Elevation Data Exchange Program established to produce a seamless, homogenous, edited TDF product from the initial raw data.

GeoData Cooperative

The GeoData Cooperative delivers global-scale, highly accurate 3D data layers through dynamic data services that meet real world military tempos. The program applies innovative algorithms, automation, machine vision, and high-performance computing to expedite the creation of high-resolution elevation models. The GeoData Cooperative’s mission is to modernize foundation GEOINT data production methods by leveraging the people, capabilities, technologies, and multi-INT data sources that exist across .gov, .org, .com, .mil, and .edu organizations. Production is currently ongoing for a global, high-resolution (2-meter) digital elevation model that will be completed by 2025. Data from this program is available from GRiD.

Visit the GeoData Cooperative website https://www.geodatacooperative.com/

Elevation Surface Types: Digital Surface Model (DSM) vs. Digital Terrain Model (DTM)

Digital elevation models (DEM) are divided into two different surface types: reflective and bare earth. A bare earth DEM, also known as a digital terrain model (DTM), portrays what the terrain would look like if all vegetation and cultural features are removed. This surface type can be used to determine slope and characterize terrain. A reflective surface DEM, also known as a digital surface model (DSM), portrays vegetation and cultural features such as buildings. This type of data may be used for general situational awareness, navigation and detection of vertical obstructions.

Data Type: Finished vs. Raw

Finished data products are created or derived from a raw format, processed, and then finished to a certain product specification. Raw data do not conform to the same strict standards as finished products and users should be aware of potential data errors when using raw data which may include:

• Spikes and Wells
• Void
• Missing or incorrectly portrayed landforms
• Random Noise
• Unfinished hydrology. Most methods used to create raw elevation data do not detect or process hydrology. Hydrology surfaces may be represented as void or noise in raw data.

Levels of Data Resolution

Level of data resolution refers to the ground sampling distance, or post-spacing, of elevation data. Resolution is typically defined in either geographic reference (arc second), or rectangular grid (precise meter) spacing. A smaller post-spacing gives the data a higher resolution and therefore more terrain detail. High resolution data comes with a price in terms of larger file sizes, potential increase in processing times, limited coverage areas, and typically higher production costs. The following table defines data levels and resolutions:

Elevation Accuracy

Closely related to resolution is accuracy. The accuracy of an elevation dataset is defined in terms of Absolute Horizontal, Absolute Vertical, and Relative Vertical. Absolute Horizontal accuracy refers to how well the latitude and longitude (y, x) location of each elevation value is known. A better horizontal accuracy means that ridgelines and other features are more likely to be correctly positioned with respect to the horizontal datum. The absolute vertical accuracy refers to how well the published elevation is known with respect to the vertical datum. In other words, how close to the actual ground surface is to the published elevation. This is in contrast to the relative vertical accuracy which describes how accurate an elevation value is in relation to its neighboring elevations. Accuracies for elevation products are published at the 90% level, meaning that the given elevation is within plus or minus the stated accuracy 90% of the time.

Data Downloads ^{PKI certs required}

NGA products can be downloaded using the Geospatial Repository and Management (GRiD) System and the Map of the World (MoW) "Download NGA Products" plugin.

• GRiD
• MoW
  • Click the "Plugins" icon:
    
  • Click the "Download NGA Products" icon:
    
  • Click:
    
  • Click the "Terrain" product type:
    
  • Click the "overlays" icon next to the desired product to view footprints. You may be required to zoom in further before downloading using selection tools.
    

Services ^{PKI certs required}

Allows visualization via the IC Portal or ArcGIS desktop (download). After selecting the link below, additional viewing options may be available by following the link under the "Map Contents" heading.