3D rated points 2014

Altimeter data from the territory of the Hauts-de-Seine seedlings of irregular 3D-rated points (XYZ) resulting from a winter 2014 LiDAR aerial acquisition.

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The semi-point altimetry data in XYZ format is a product resulting from the 2014 LiDAR aerial acquisition. This is a decimation of the points of the floor class of LAS files. This means that only one point is kept in an area of 10 points in the ground class of the original LiDAR point cloud. We get a more lighter ground but strictly soil. Other LiDAR classes such as vegetation or building are no longer available. Unlike the LAS format, it is not a format called a cloud of points, consisting of a set of points not dissociated from each other, but a format of type TXT listing the XYZ coordinates of each point.

**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 3D rated point data is made available in 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 semis of points in XYZ format makes it possible to generate, with integration of slope break lines, an MNT by a lighter network of irregular triangles (TINs) and thus easier exploitation of field data: 3D base for urban 3D models, level curve calculations, field modeling,...

**Related data**

Open data portal of the Hauts-de-Seine Department

* Link to the Geographical Mapping Dataset Reference: [Geographic Reference Mapping](https://opendata.hauts-de-seine.fr/explore/dataset/fr-229200506-maillage-geographique-de-reference)
* Link to the 2014 MNT raster dataset: [MNT raster 2014](https://opendata.hauts-de-seine.fr/explore/dataset/fr-229200506-mnt-raster-2014)
* Link to LiDAR dataset classified 2014: [LiDAR classified 2014](https://opendata.hauts-de-seine.fr/explore/dataset/fr-229200506-lidar-classifie-2014)