Sources

Most of the data used during my internship comes from remote sensing. Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object and thus in contrast to on-site observation. For elevation data the most common remote sensing techniques are Photogrammetry, Airborne Lidar Scanning.

Photogrammetry

Photogrammetry is a method for obtaining elevation data by using photographs taken from different angles.

Airborne Lidar Scanning (ALS)

Airborne Lidar Scanning is a method for obtaining elevation data by using a laser scanner mounted on an airplane. It determines the distance to an object by measuring the time delay between the transmission of a laser pulse and the detection of the reflected signal.

Data bases

I used the data base of the Institut national de l’information géographique et forestière (IGN) to get the elevation data covering the whole France. The data are dispatched in 3 different data bases:

  • RGE ALTI : Référentiel Géographique à Grande Echelle (RGE) contains data on the elevation of the terrain (DTM). The data are obtained by photogrammetry, ALS and on-ground measurement. The resolution is 1 meter.

  • MNS Corélé : Modèle Numérique de Surface (MNS) contains the elevation of the above ground features (DSM). The data are obtained by photogrammetry. The resolution is 0.5 meter.

  • BD TOPO : Base de Données TOPOgraphiques (BD TOPO) contains information on the position of the features on the ground. It gather data coming from various sources (land registry, classification of the aerial photographs, …​).