MNT 2014 (raster)

Altimeter data for the Hauts-de-Seine territory of type MNT raster from a winter 2014 LiDAR aerial acquisition.

MNT raster data in ASC format is a product from the 2014 LiDAR aerial acquisition. These are so-called raster files from a matrix. The raster NTM is calculated from a TIN (network of irregular triangles constructed from slope break lines and a ground point cloud) and re-sampled according to a matrix defining a step to the NTM i.e. 1 meter in our case. This means that each pixel of the matrix (ASC file) is spaced by 1 meter in planimetry. The raster NTM is therefore an interpolated data from the LIDAR acquisition and therefore less precise in itself because it does not reflect the actual field data such as slope break lines or LiDAR point cloud.

Context

The Hauts-de-Seine Department carried out an aerial LiDAR acquisition on its territory in early 2014. A LiDAR acquisition has the advantages, especially in periods without leaves in vegetation, of being able to acquire more data on the ground under vegetation (for example wooded areas) or in bare agricultural areas. Thanks to these advantages, it is possible to generate more accurate Digital Field Models (DTMs).

The technical characteristics of this LiDAR acquisition are as follows:

• Projection: RGF93-CC49/IGN69
• Density: 16 pts/m²
• Hard surface planimetric precision class: 0.1 m
• Period of air acquisition: 2-8 April 2014

This LiDAR acquisition is the basis of several products that complement the Hauts-de-Seine Department’s altimetry data supply.

Lexic

LiDAR
Light Detection and Ranging. It is a remote measurement technique based on the analysis of the properties of a beam of light returned to its transmitter. The LiDAR acquisition tool can be ground or airborne. In the case of an aerial acquisition, processing software is used to classify the properties of the light beam and to restore its nature: building, water, vegetation, soil,...
MNT
Digital model of field. It is a numerical representation of the shape of a natural terrain or not calculated from various data whose planimetric and altimetric coordinates are known: seedlings of ground or photogrammetry points, topographical lines raised on the ground or by photogrammetry, LiDAR points, point seedlings correlated from aerial images. The NTM represents only ground data. Overground data (buildings, vegetation, etc.) do not appear. The altitude value of these areas corresponds to the ground value.
MGR
Geographical linkage of Reference. Grid of slabs of 1 km by 1 km allowing the territory of Hauts-de-Seine to be regularly gridded.

Specific comments

The provision of raster NTM data shall take the form of:

• 1 km x 1 km georeferenced tiles conform to the Geography Reference Maillage (MGR) of the Hauts-de-Seine Department.
• Of “zip” files containing the georeferenced LAS tile.
• The syntax used for the naming of tiles: “XXXX_YYYY_LAS”, uses the XY coordinates in RGF93-CC49 according to the Xmin_Ymax standard of the relevant slab.
• The download of a slab is done by clicking on the slab in the table or in the map and downloading the associated zip file.

The MNT raster in ASC format allows you to quickly visualise altimetry data in a GIS environment, calculate for visualisation in a map and a GIS of simple level curves, makes it possible to serve as a basic terrain for an urban 3D model,...

Related data

Open data portal of the Hauts-de-Seine Department

• Link to the Geographical Mapping Dataset Reference: Geographic Reference Mapping
• Link to LiDAR dataset classified 2014: LiDAR classified 2014
• Link to dataset 3D rated points 2014: Points rated 3D 2014