Shuttle Radar Topography Mission

Introduction

NASA image of Endaevour taking of 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 mission STS-99. The raw data was collected using an instrument named “Spaceborne Imaging Radar-C”. The raw data was later processed and released as usable digital grid files.

NASA has released two versions ofthe SRTM dataset; one with a 3 arc second resolution (90 m grid size) and a near global coverage, and one with 1 arc second resolution (30 m grid size) but only available for the US and its terrotories. Currently this latter 30 m dataset is not available through the EMD online services, but it is possible to manually download the data and load the data into a line object.

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 is available directly from within WindPRO. The data can be reached 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, then WindPRO also supports importing the *.hgt files that can 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 3 arc seconds, i.e. approximately 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.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. Currently this dataset is currently not available through the EMD online services, but it is possible to manually download the data and load the data into a line object.

External Links

• Original data is 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

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.