Terrain Data (GeoTIFF): IGN - Institut national de l'information géographique et forestière (France) DSM Model

You can use the Plex-Earth features to create terrain models from free, quality data you can find online.

One notable example of these data is the GeoTIFFs provided by the IGN - Institut national de l'information géographique et forestière (France), which offers a wealth of free, high-quality imagery and terrain data for France.

Here, we will present how to use Plex-Earth to create terrain models from Correlated Digital Surface Models:

A DSM (digital surface model) describes the shape of the land and surface of the territory. 
In addition to the terrain, this regular mesh provides the elevation of all elements 
above the ground, such as vegetation, buildings, or engineering structures. 
It is produced by "correlating aerial images" acquired to update the ORTHO® database. 
For each department, we therefore obtain a consistent model of the land and surface 
of the territory, as up-to-date as the corresponding orthoimage.

The data are disseminated by France's district departments.

Their resolution is 50cm.

A: Download the Data for your Area of interest

1) Visit the following URL

2) Extract the files from your zip folder

3) Select the proper GeoTIFF for your area

i) Locate your area in Google Earth or Google Maps

ii) Convert Lat/Long to X, Y of Lambert 93 Projection

iii) Locate the proper tiff

B: Use the GeoTIFF to create a Terrain Model

1) Start Plex-Earth and apply a coordinate system

2) Use the command Create Terrain from GeoTIFF

3) Select Area from GeoTIFF preview

4) Select Type of Surface

(Optional)

5) Use the command Create Terrain from GeoTIFF for the second file 

6) Select the remaining Area from the GeoTIFF preview

7) Select the Type of Surface for the remaining Area

8) Create a Terrain Model using all the points for your area

Α: Download the Data for your Area of interest

1) Visit the following URL:

https://geoservices.ign.fr/modeles-numeriques-de-surfaces-correles

When you scroll down, you will see multiple download links for your data, per France's district departments.

Scroll until you find the district of interest and click on the respective link(s) for the download to start. Files are large, so the download might take some time.

2) Extract the files from your zip folder

Right-click the downloaded zip folder and extract all the folders.

3) Select the proper GeoTIFF for your area

Open the folder, and then navigate to the first file:

You will see a list of multiple TIFFs, so you need to select the proper one for your area.

To do so, we need to break down the parameters of the name of each file. To understand this, check the following example:

The next step would be to find the right tile by converting your area's lat, long coordinates to X, Y of Lambert 93 Projection.

i) Locate your area in Google Earth or Google Maps

Find your area in Google Earth or a similar app, and note its Lat/Long coordinates

For our example: Lat: 48.818520°, Long: 2.346542°.

ii) Convert Lat/Long to X, Y of Lambert 93 Projection

Use any converter such as EPSG.io.

For input, use Lat/Long, and use projection Lambert 93 for output, then Transform.

Then, take the output coordinates.

X: 652018.8479442275

Y: 6857804.591243857

Since the grid is by 1 km, divide the values by 1000, and the result will be the following:

X: 0652

Y: 6858

iii) Locate the proper tiff

With the above calculations, the correct folder for our area would be:

75-2024-0652-6858-LA93-0M50.tif

B: Use the GeoTIFF to create a Terrain Model

There is already a detailed tutorial on how to create a Terrain model from a GeoTIFF.

Tutorial: Create Terrain from GeoTIFF

Check also the steps below:

1) Start Plex-Earth and apply a coordinate system

The coordinate system applicable is Reseau Geodesic Francais 1993/ Lambert 93 (EPSG: 02154)

Open CAD, and start Plex-Earth, then select Assign Georeference and apply Coordinate System. Choose France, and find the respective coordinate system.

Tutorial: Apply a Coordinate System

Once finished, this is the one that you should have applied.

2) Use the command Create Terrain from GeoTIFF

Select the respective command from the Plex-Earth ribbon

and load the proper GeoTIFF.

3) Select Area from GeoTIFF preview

In our case, the area of interest is included in the GeoTIFF, but only partially.

This will not always be the case; it depends on our area and each tile's limits. 

For cases where the entire area is included, we just proceed to select the area and resolution and create our terrain model. 

Here we will proceed with this part first, and then select a second GeoTIFF.

At the moment, we are going to import the part of the area included in this GeoTIFF, using the Select Area Button.

4) Select Type of Surface

For this case, which will require a second GeoTIFF, we select to Import Points. 

5) Use the command Create Terrain from GeoTIFF for the second file

Since we missed a part of the left side of the area of interest, we are going to use the 75-2024-0651-6858-LA93-0M50.tif file, as well.

6) Select the remaining Area from the GeoTIFF preview

From the preview, check that the remaining area of interest is there, so select it and proceed.

7) Select the Type of Surface for the remaining Area

Again, select Import Points.

8) Create a Terrain Model using all the points for your area

Now, you have two separate point blocks of points, so what you need is to add them together to a final terrain model.

Then, use the Create Terrain from Objects command of Plex-Earth, and select the points.

There is already a detailed tutorial on how to create a Terrain model from objects.

Tutorial: Create Terrain from Objects

You will end up with a terrain model like this:

After that, you can use this model as any Plex-Earth terrain model, edit your data, insert it as points or mesh, drape imagery, create 3D models, and other options.

We hope that you have found this tutorial on using the IGN - Institut national de l'information géographique et forestière (France) DSM Model helpful. Feel free to contact us at support@plexscape.com for any questions you may still have.

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