Local coordinate systems in MapTiler Cloud

MapTiler Cloud can host documents in map projections other than the standard Web Mercator. This is useful for integrating with some sources of data and to conform to region-specific expectations of how maps should look like. In this article, we will explain how this functionality is handled in MapTiler Cloud and what the limitations are.

Introduction

Most online maps use the web Mercator projection and tiling that was popularized by Google Maps. However, there are other coordinate systems and map projections in common use. Many countries have national standards for collecting geographic information that uses local coordinate systems. Each system is then usually displayed in a specific map projection.

The use of local coordinates and projections predates the modern era of GPS measurements in the global WGS84 coordinate system and the ubiquity of online maps. Cadastre maps, road maps, and building plans are examples of documents that are usually available only in local coordinates.

People are also used to the way their country or region looks on a map in the local projection. The Mercator projection notoriously distorts regions close to the north and south poles, and even regions further away might look unnatural.

Tilesets

We offer both raster and vector tilesets for some European countries on the tileset listing page. You can also upload your own.

The MBTiles format of tileset container files is specified to always be in web Mercator. To upload a tileset in any other coordinate system, you have to use the GeoPackage format. MapTiler Engine is capable of producing raster GeoPackage tilesets in any projection. However, please note that it can only produce vector GeoPackage tilesets in web Mercator for now.

Maps

There are maps available for several European countries on the map listing page. Due to technical limitations, they can’t be customized for now. The map editor also works only with Mercator maps. You can, however, import a style JSON that you have prepared manually.

The reason behind these limitations is that the MapLibre GL style specification itself is formally limited to web Mercator. It is possible to display maps in other projections as well, but zoom level and centering calculations still happen in Mercator internally in MapLibre GL SDKs, so configuring them up is challenging.

Datasets

We store dataset feature geometries in WGS84 and publish them in the GeoJSON format. Due to internal limitations of MapLibre GL SDKs mentioned above in the Maps section, it is not possible to add datasets as sources to maps operating in local coordinate systems.

Conclusion

Local coordinate systems and projections are supported for tilesets. Configuring them for maps is possible but difficult. We do it for the maps we publish, but unfortunately, it’s not possible at this time to do it automatically in the customization and editor tools.

Useful links

What are coordinate systems
Maps, tiles, data
Vector tilesets in MapTiler Engine