Multiple CRS support

[gchoqueux]

Feature description

• Add the multiple crs projections support.
• Visualize simultaneously vector or raster data with different projections

How to develop it

There are different way:

1. The projection texture : use shader to re project data
2. Use projection grid mesh to re project data (resampling data with a vector geometry)

Useful links

Map box

• reprojection example
• reprojection information

Openlayer

• reprojection example
• reprojection information

[jailln]

Nice initiative! My inputs on this subject:

1. I think we should clarify what is the actual support of itowns on this subject. For what I know, it seems that:

• It is already supported for EPSG:4978 and 3857 in globe view
• terrain elevation can be passed in any CRS and is reprojected in the view crs

Is that correct ? If yes, we should indicate it clearly in the documentation, either in the corresponding classes or maybe in a master documentation describing the general philosophy and features of itowns. Maybe something like a developer guide for users of the API like what's done for deck.gl?

2. Could you elaborate on the two options you provide ? And what are the pros and cons ? Is the first way for rasters and the second for vectors ?

[gchoqueux]

I think we should clarify what is the actual support of itowns on this subject. For what I know, it seems that:

The globe view support

• For ColorLayer : EPSG:3857 and EPSG:4326
• For ElevationLayer : EPSG:4326
• For GeometryLayer with vector source : Any projections

We will add clarifications in itowns tutorials.

Is the first way for rasters and the second for vectors ?

It's two way to display data on terrain with ColorLayer or ElevationLayer.
I think the best way is projection grid mesh, this's the choice of OpenLayer and MapBox.
I will detail later the technique and the developments