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Will the maps of La Palma have to be changed after the eruption?

The La Palma volcano is one of the natural phenomena that has caused the most scientific and media impact in recent years. The damage to the economy and to the lives of the affected families has sensitized us all. The consequences on the territory are being devastating. The landscape has been modified: houses, plantations, roads, power lines and water pipes have been destroyed.

Engineering in Geoinformation and Geomatics deals with the treatment of geographic information. His tasks include the making of maps, three-dimensional models of the terrain and other forms of representation of the Earth. As a result of the volcano eruption on La Palma, there is an extraordinary opportunity to reflect on the importance of cartography.

Updating the cartography is a necessity that in current times is demanded with greater frequency and accuracy. We live in a constantly changing society. Development implies a gradual modification of the territory. Changes in land use or the implementation of new infrastructures are made through maps and mathematical modeling previously planned. For their part, natural phenomena such as the unpredictable volcanic eruption are challenges for geomatics.

The volcanological news raises a series of questions that we hear in the media: can the old boundaries of the plots destroyed by the wash be restored? How will the new land reclaimed from the sea be reflected on the maps? How will the cartography collect the damage to the infrastructures or the modifications that the topography has suffered?

Daily we consume geoinformation . From the moment the data is obtained until the map is generated, there is a set of techniques and disciplines associated with geomatics that allow information to be organized and classified for correct visualization and analysis.

These include, but are not limited to, geodetic positioning methods, as well as tools for capturing images of the terrain: photogrammetry and remote sensing. Finally, maps and other cartographic products such as orthophotographs and digital terrain models are distributed through the internet.

Will a redefinition of the geodetic network be necessary?

The first step is to know the deformation that the island as a whole has suffered. Especially the area directly affected by the lava, which is currently in charge of the geodetic monitoring network arranged throughout the entire island of La Palma. Composed of a series of GNSS stations ( Global Navigation Satellite System, global navigation systems by satellites) , it continuously determines the position of its points and therefore the deformations of the earth’s crust and the velocity field that can be produced in them by seismic and volcanological effects.

In addition, and in order to verify the results obtained by these geodetic procedures, InSAR techniques (which are radar interferometric technologies from satellites) have been incorporated into these studies in the last decade. These techniques made it possible, for example, to locate the underwater volcanic source of El Hierro in the 2011 eruption, and replaced the classic (terrestrial) geodetic observations that were carried out in the second half of the last century. Especially since the Teneguía eruption in 1971, in order to collaborate with the seismic, hydrological and fumarological networks of the island of La Palma.

These geodesic networks provide us, in their new definition after the volcanic and seismic events, the geometric structure for the representation of both the new terrains that the lava has formed (terrestrial or oceanic) and the variations of the existing ones, and in it new uprisings will be supported.

Will it be necessary to carry out new topographic surveys?

At the present time, with the volcano still erupting, it is not so much a matter of making a formal mapping of the area but of knowing the evolution of the phenomenon. Being a changing process and with multiple effects, a multiscale analysis makes perfect sense. This would not have been possible a few years ago because data collection involved an investment of time incompatible with the speed of change.

Currently there are a variety of sources of information unimaginable long ago. On the one hand, the acquisition of images and videos from drones allows the laundry to be monitored practically in real time.

On the other hand, from space, the observation satellites of the territory not only provide images in the visible spectrum, but also have infrared and thermal sensors to know the physical and chemical parameters of the streams, or sensors in the microwave spectrum. capable of detecting subsidence or outcropping of the ground in the order of centimeters.

Currently the problem does not lie in obtaining data but in processing and analyzing it. The geoinformation and geomatics engineer is the best trained professional for these tasks.

At this time, with the volcano still erupting, the cartography that is being drawn up is what are called emergency maps (fastmaps, in its Anglo-Saxon sense) that allow decisions related to civil protection to be made.

In the future, the information that is currently being collected will allow more detailed and leisurely analyzes, helping to reconstruct the different phases of the eruption, develop mathematical models and strengthen new volcanological hypotheses by specialists.

When the land has settled and cooled down definitively, the acquisition of specific images for this aspect will allow the topographic map of the area to be re-elaborated in order to proceed with the zoning of the plots according to the legal and cadastral information of the properties.

Angel Luis Muñoz Nieto, Department of Cartographic and Terrain Engineering, University of Salamanca; Carlos Pérez-Gutiérrez, Professor and researcher in photogrammetry, remote sensing and spatial data infrastructures, University of Salamanca and Manuel Pérez,, University of Salamanca

This article was originally published on The Conversation. Read the original.

The Conversation

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