Help Content > Import Data > DEM Extraction

Purpose

This tool downloads, mosaics and optionally resamples the enhanced global elevation model Global Multi-resolution Terrain Elevation (GMTED-2010), which replaces GTOPO30.

The GMTED-2010 is a standard mapping format derived form the collaboration between U.S. Geological Survey (USGS) and the National Geospatial-Intelligence Agency (NGA). It ncludesthe global Digital Terrain Elevation Data (DTED) from the Shuttle Radar Topography Mission (SRTM), Canadian elevation data, Spot 5 Reference3D data, and data from the Ice, Cloud, and land Elevation Satellite (ICESat)

The GMTED-2010 is available in the SARscape installer at 15 arc-sec resolution.

Technical Note

The GMTED-2010 is a standard mapping format designed by the NGA. Each file or cell contains a matrix of vertical elevation values spaced at regular horizontal intervals measured in geographic latitude and longitude units.

The GMTED-2010 seven new raster elevation products based on the aggregation methods:

1.minimum elevation,

2.maximum elevation,

3.mean elevation,

4.median elevation,

5.standard deviation of elevation,

6.systematic subsample, and

7.breakline emphasis.

The provided raster is characterized by 15 (450 m) arc-second spatial resolution.

The original GMTED-2010 tiles in geotiff format can be downloaded from the USGS Earth Explorer ath the GMTED2010 Viewer clicking on a map tile. Drag a rectangle to choose multiple tiles is an option as well. The aggregation method and the spatial resolution is described in the filename.

Note: The 15-arc-second SPOT 5 Reference3D data used for filling SRTM voids in Africa, Central America, Asia, and Australia was graciously provided by Spot Image and IGN.

The default grid size is set to 450 m, which corresponds to the approximate DEM at mid-latitudes.

User should be aware that the GMTED2010 products are substantially better than the aggregated global statistics; however, large areas still exist, particularly above 60 degrees North latitude that lack good elevation data.

Input Files

Input File List

Input file name(s) of the image(s) to be used as geographic reference for the Digital Elevation Model extraction. This file is mandatory if the cartographic co-ordinates are not specified. In case a geocoded image is used, the "Cartographic System" specified below must be the same of the reference image. The geographical extent of the output Digital Elevation Model corresponds to the common coverage of the Reference file list.

DEM/Cartographic System

Output Projection

The parameters relevant to the Cartographic System of the output Digital Elevation Model must be entered:

State

Definition of the country or general projection systems.

Hemisphere

Definition of the hemisphere. This is chosen according to the selected State and Projection.

Projection

Definition of the projection system of the selected State. In case that a general projection system is selected in State, the Projection is automatically set.

Zone

Definition of the zone. This is chosen according to the selected State and Projection.

Ellipsoid

Definition of the ellipsoid. This is chosen according to the selected State and Projection.

Datum Shift Parameters

Definition of the datum shift parameters. These are chosen according to the selected State and Projection.

Reference Height

A reference ellipsoidal height can be provided. Default Reference Height is 0.

Parameters - Principal Parameters

Generate Slope

By setting this flag, three slope files are created: slope east-west, slope north-south (between -90 and 90 degrees), and a third output representing the slope magnitude (sqrt(ew^2 +ns^2)), with values between 0 and 90 degrees.

By setting the following parameters it is possible to specify a spatial region for the Digital Elevation Model extraction (co-ordinates are referred to the output cartographic reference system).

West

The Westernmost cartographic coordinate.

East

The Easternmost cartographic coordinate.

North

The Northernmost cartographic coordinate.

North

The Southernmost cartographic coordinate.

X Grid Size, Y Grid Size

The grid size of the output data must be defined. The default measurement unit is meters.

If a Geographic projection was specified and grid size values higher than 0.2 are entered the measurement unit will be assumed to be meters. if values lower than 0.2 are entered the measurement unit will be assumed to be degrees.

A different grid size can be specified for the X and Y dimensions.

Parameters - Global

It brings to the general section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.

Parameters - Other Parameters

It brings to the general section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.

Output Files

Output DEM file

Output file name of the extracted and mosaiced Digital Elevation Model. This file is mandatory.

_dem

Extracted Digital Elevation Model, with user-defined projection and grid size, and associated header files (.sml, .hdr).

_slope

Combined slope image and associated header files (.sml, .hdr).

These last three files are generated only if the relevant flag is set.

Details specific to the measurement units and nomenclature of the output products can be found in the Data Format section.

General Functions

Exec

The processing step is executed

Store Batch

The processing step is stored in the batch list. The Batch Browser button allows to load the batch processing list.

The window will be closed.

Help

Specific help document section.

Specific Function(s)

None.

General Tools - Digital Elevation Model Extraction - "GMTED 2010"

General Tools - Digital Elevation Model Extraction - "GMTED 2010"