Shuttle Radar Topography Mission

Introduction

NASA image of Endeavour taking off on its STS-99 mission

The Shuttle Radar Topography Mission (SRTM) data originate from an 11-day mission flown by the space shuttle Endeavour back in February 2000, on its STS-99 mission. The raw data were collected using an instrument named “Spaceborne Imaging Radar-C”. The raw data were later processed and released as usable digital grid files.

Availability from within WindPRO

Satellite Image with DEM Overlay. The image shows a part of the Ometepe Island in Lake Nicaragua with SRTM height contour data.

The data are available directly from within WindPRO. The data can be accessed from the online-services in the following objects:

• Line Object (with purpose to height contour lines)
• Elevation Grid Object

In addition to loading the data directly from the EMD online services, WindPRO also supports importing the original *.hgt files that can also be downloaded from other internet sources.

Data Type

The SRTM data are delivered as gridded data with a spatial resolution of the dataset corresponding to 1 arc second and 3 arc seconds, i.e. approximately 30 m and 90 m distance between grid points. As a part of the processing of the SRTM data from our EMD server, the user has an option of choosing whether the data downloaded should be received as either raw gridded data or converted to height contour lines. In order to use the data for energy yield calculations, the data must be converted to contours.

The original SRTM data are stored as tiles sized 1 degree x 1 degree.

Coverage

Near-global coverage of the SRTM dataset

About 80% of the total landmass of the Earth is mapped by the STRM data, covering all land between 56 degrees south and 60 degrees northern latitude. A view of the data coverage is shown in the figure below.

Versions and Data Sources

Different versions of the SRTM data exist; at EMD we currently distribute the STRM data version 3 in a 3 arc-second resolution (90 m grid resolution). The difference between various versions is primarily that more error checking and validation is applied at later versions.

An alternative SRTM dataset with a higher spatial resolution of 1 arc second (about 30 m) is also available for the US and its territories. Ultimo 2014 - NASA/JPL (the team around the SRTM data) - have started releasing the 1 arc second data for selected parts of the world including regions like Europe, South America, North America and Africa. At this time of writing - we are working to make this dataset available (possibly in the upcoming release of WindPRO 3). So currently the 1 arc-second dataset is not available through the EMD online services, but it may be possible to manually download the data and load the data into a line object.

External Links

SRTM data in Northern Ireland: Left: As Height Contours, Right: As Gridded Data.

• Original data are available from the NASA website at http://www2.jpl.nasa.gov/srtm.
• More information on SRTM is available at wikipedia at http://en.wikipedia.org/wiki/Shuttle_Radar_Topography_Mission
• Direct download of 1° x 1° hgt.zip files at http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/

Acknowledgement

NASA, team around STS-99 and the US public are thanked for making this great digital elevation dataset available in the public domain and thus for aiding the development of renewable energy.