ECOGIS Geomatics - SRTM data

What is SRTM data and where can I get it?

In February 2000 the Shuttle Radar Topography Mission (SRTM) took place to get the world's most comprehensive set of elevation data. Though the data with the best resolution is subject to military use, the resolution of the data that is available for the public is also by a multiple better than anything else, at least in many parts of the world.

Since July 7, 2004, SRTM data is available from all parts of the world between 60 deg. north and 60 deg. south.:
North_America from 15 deg N to 60 deg N sampled at 3 arcseconds
South_America from 15 deg N to 60 deg S sampled at 3 arcseconds
Europe and Asia from 60 deg N to 10 deg S (Asia) and 35 deg N (Europe) respectively, sampled at 3 arcseconds
Africa from 35 deg N to 35 deg S sampled at 3 arcseconds
Australia and Oceania sampled at 3 arcseconds
Unites_States: All Unites States SRTM DEMs are available sampled at 1 arcsecond

You can download SRTM data with http or ftp access from the Earth Sources Observation Systems (EROS) Data Center at this URL:
ftp://e0srp01u.ecs.nasa.gov/srtm

NASA seems to change the name of the data location from time to time. The latest places they've been located were:
ftp://e0mss21u.ecs.nasa.gov/srtm (2006)
ftp://e0dps01u.ecs.nasa.gov/srtm (2005)
http://edcsgs9.cr.usgs.gov/pub/data/srtm (2004)

Please don't ask me about the location if you can't access it. Anyway, I'd be glad about any information if the location changes next time.

All files are zip-packed and can be unpacked with any file archiving utility (e.g. pkzip). You can extract multiple packages with Total Commander or WinRar easily.
The file names specify the coordinate of the lower left corner of each tile. E.g. N52E009.hgt means that the lower left corner is at 52 deg. north and 9 deg. east. Each tile (be it in a resolution of 3 arc seconds or 1 arcsecond per pixel) covers an area of 1 x 1 degrees.

How can I work with SRTM data?

The hgt files are provided at EROS Data Center as BIL data (band interleaved by line) without a file header. The file header can be created manually for each SRTM tile which can be troublesome. A lot more convenient way to create grids from SRTM tiles is - presumed that you have ArcView and Spatial Analyst - to import the tiles with the batch import functionality of the extension Grid Machine. Click here to obtain information about the functionalities and how to get Grid Machine.

Of course you can also get converted SRTM data as ArcGrids or other optional other formats from us. Just send an email and ask for prices. Below you find the instructions how to import SRTM data directly yourself.

Import SRTM files with Grid Machine

The dialog shows the functionalities of Import machine in Grid Machine 6.15 by ECOGIS Geomatics. Import machine is only one out of several tools of the ArcView Extension Grid Machine, and once registered it allows batch import not only of SRTM data, but also of ASCII grids (ArcView, Surfer and GRASS format), point data and images. Import machine allows the import (i.e.: conversion to grids) of multiple files at once. The file names are preserved, so you get grids with the same names as the files you are importing. You can give Grid Machine a try, but only for 90 days and for one grid at once concerning SRTM data import.

Here's a picture of the SRTM file N52E009.hgt (Hannover, Germany) as an ArcView grid imported with Grid Machine:

Image file:

Full image:
n52e009.jpg

Worldfile:
n52e009.jgw

Requires:
JPEG (JFIF) image support (jfif.avx)

Grid:

ASCII-Grid (*.asc, zipped):
n52e009.zip

Legend file:
srtm.avl

Requires:
Spatial Analyst (spatial.avx)

For more information about SRTM data, please take a look in the documentation on the SRTM homepage.

How can I get the data into my local coordinate system (e.g. UTM)?

You can do the transformation in three steps:

1. Export the grid from an unprojected View as dBase table using the Export utility of Grid Machine.

Export SRTM grids with Grid Machine

A dBase table is created which is located in the specified directory and added to your ArcView project.

2. Create a new blank view with the projection of your local reference system (e.g. UTM - 1983)

UTM Projection

3. Reimport the data with Grid machine using the preferences below. It is strongly recommended to specify the cellsize if you import data in a projected view, because the automatic cellsize only produces sensible values in unprojected views.

Import dBase data with Grid Machine

Click OK to receive a grid in your local coordinate system. Please send an email to the author if you have any questions.

URL:http://www.ecogis.de/srtm.html
Deutsch: http://www.ecogis.de/srtm_de.html

Homepage:http://www.ecogis.net
Deutsch: http://www.ecogis.de/

last edited: Johannes Weigel, Jan. 8, 2007