M.L. Advis, C. Andrade

Military Geographic Institute of Chile


Chile, a long and narrow strip of land, extends from about latitude 17º 30´ South down to the South Pole in the Chilean Antarctic territory. The topographic map series at 1:50,000 scale constitutes the official cartography of the country and is made up of about 1200 maps in formats that vary from 15´x 15´ to 15´x 22´ according to the latitude.

The southern zone of the country has unique features making the creation of the topographic coverage especially difficult.

Given that a large part of the cartography of the Southern Zone of Chile has to be created from the beginning, which requires a lot of time using the traditional methods of aero-photogrammetric restitution, research was carried out to find a way to do this that would be faster yet maintain the technical characteristics of the existing cartography of the rest of the country.

The SRTM (Shuttle Radar Topography Mission) carried out on the space shuttle offered an alternative, so various tests were carried out, specifically with SRTM 2 (30 meters). Its match with terrain control points, aerotriangulated points, planimetry and coast lines was checked. The data was not good in all situations, but when the contours were generated on the basis of the DTM from the SRTM, this yielded a very good result.

Once the greater part of the contours and of the other information, that is, the roads, spot heights, coast lines, and population centres was gathered, the rest was obtained by means of restitution with the existing photographic coverage. It was also necessary to generate the contours in those sectors where the SRTM provided no information. Once the contours from SRTM and from aerophotogrammetric restitution were combined, the result was excellent.

The most important gain from this experience was that information from two different techniques could be combined to complement each other and achieve a good final product, thus saving time and man / hours at work. The information from SRTM2 that enabled the creation of the contour lines at every 50 meters matched information to a 100 % fit with the digital restitution information, the source for which was an aerial photo coverage. Between the two of these, the creation of the cartographic coverage was created at 1:50,000 scale with a substantial saving in time and human resources.

This has been an experience entirely valid for those countries which have not achieved a cartographic coverage of their territory.