Download and install CloudCompare
CloudCompare is a 3D point cloud processing software (such as those obtained with a laser scanner). It can also handle triangular meshes and calibrated images.
Download point cloud data from IGN
As part of the national LiDAR HD program, IGN produces and distributes 3D LiDAR maps of the whole of France’s soil and above-ground. The data disseminated includes raw or classified point clouds and 3D digital models (DTM, DSM, DHM, etc.).
The 3D point clouds acquired as part of the LiDAR HD program are first classified into several classes (soil, water, vegetation, buildings, bridges, perennial surface) and then give rise to the production of DTM (digital terrain models), DSM (digital surface models) and DHM (digital height models).
All acquisitions and productions are spread over 5 years according to the priority needs expressed by the project’s national and local sponsors and their uses.
One the map, each tile is 1km x 1km wide More explanations on the downloading process and the ability to export a scan’s list Ability to draw a polygon and download the whole list? Explore and script
Importing IGN’s data in CloudCompare
- Drag and drop in CloudCompare (one or multiple files)
- Press ‘Apply All’ and ‘Yes to All’
Manipulate data in CloudCompare
- If multiple point clouds imported, merge them (Edit > Merge)
- Select the point cloud
- On the bottom part of the left panel, under the ‘Scalar Fields’ part, choose ‘Classification’ in the dropdown menu
- Then we’ll filter the point cloud by classification: Edit > Scalar fields > Filter by value
- Enter value 1 to 1 and press Export, we now have an instance of the ‘unclassified’ data
- Repeat the operation, but enter value 2 to 2 and press Export, this is an instance of the ground data
- Repeat until you have all the data exported for each classification
- Set unique colors for each classification: Edit > Colors > Set unique
IGN’s data classification
The following table recapitulates the values for each classification:
| ID | Classification |
|---|---|
| 1 | Non classé |
| 2 | Sol |
| 3 | Végétation faible |
| 4 | Végétation moyenne |
| 5 | Végétation forte |
| 6 | Bâtiment |
| 9 | Eau |
| 17 | Tablier du pont |
| Sometimes, points are also classified in classifications “64”, “65”, “67”. This must be investigated to understand the reason of this classification. It might be some noisy data that does not represent real scanned objects. |
Generating a mesh from the ground data
Once the data has been filtered in Cloudcompare, it is possible to create a mesh that fits this ground data, thus generate a ground model.
- Select the point cloud corresponding to ground data
- Compute the normals of each point: Edit > Normals > Compute
- Do not change any setup, press ‘OK’
- This might take a while
- Then, to create a mesh, go to Plugins > PoissonRecon