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Monoplotting: Using photography to record landscape changes

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Fallbeispiel einer Hangmure in Tschentetal/Egerle, Adelboden (BE)
Case study of a landslide in Tschentetal/Egerle, Adelboden (BE). a) Original image from 18 October 2011, with control points (yellow dots with red border, b) original image with digitized extent of debris flow (red lines) c) detailed map with debris flow marked. Due to the finely branched spread of the deposits, mapping in the field would have been extremely costly.

Marco Conedera was astonished when the request came in from Rio de Janeiro. The coordinator of the photography division of the Instituto Moreira Salles, an organization for cultural promotion, had stumbled across his monoplotting tool on the internet. Claudio Bozzini, Patrik Krebs and Conedera had developed the free software at the WSL site in Ticino. With monoplotting, landscape features – such as bodies of water or rocky promontories – can be digitized from any kind of photograph and transmitted with an accuracy ranging from tens of centimeters to a few meters. The only conditions the photo has to meet are that it must be available in digital format with good image resolution, and feature four or more control points (or landscape elements) that are clearly recognizable both on the photo and on a map. Using these control points, the photo can be georeferenced, which means that every pixel on the image is assigned a real coordinate.

This technique opens up com­pletely new possibilities. Based on the vast treasure trove of historical photo­graphs lying around unused in so many archives, it is now possible for the first time to quantitatively docu­ment how the landscape is changing – for example, by how many meters the tree line has risen, or how many meters of terracing once ran through a now wooded area. It is a technique that has drawn the interest of the Instituto Moreira Salles. The institute wants to use the monoplotting tool to quantitatively evaluate more than 10,000 images of Rio and other areas of Brazil, a unique collection that has existed since the 19th century.

A better understanding of the scope of natural events

The software can be used for more than just analysis of historical photo­graphs, though. It also has consider­able potential when it comes to documentation of contemporary natural events. Debris flows that occur simultaneously or in impassable areas, for example, can often be re­corded only through targeted photo­graphy. The same is true of particularly severe landslides, where the priority is on initiation of rescue operations. Monoplotting enables evaluation of these images later on in the calm of the office, and calculation of the exact extent of debris flow residue. It is an asset that has also caught the attention of the Federal Office for the Environment, which has commis­sioned Conedera and his team to program an interface capable of importing photos analyzed using the monoplotting tool into StorMe. StorMe is a database system used for land registries of natural hazard events, maintained by the cantons on behalf of the federal government. In future, cantonal employees will be able to form an immediate idea of some of the damage using the mono­plotting tool, making the process of keeping an account of natural events much more straightforward. (Christine Huovinen, Diagonal 2/16)