This article contains information about Coordinate Reference Systems (CRS) or Spatial Reference Systems (SRS) and about their usage in MapTiler Engine. You can read some general information about CRS in this article.
Each properly georeferenced map needs a valid Coordinate Reference System defined. There are thousands of coordinate systems, but the most frequently used one is WGS84. The geodata from national geospatial agencies usually come in the local coordinate system, like for example Ordnance Survey from the United Kingdom, using EPSG:27700.
Setting the CRS in MapTiler Engine
After opening your source file, if it contains embedded geodata, MapTiler Engine will automatically load it. In case the file does not contain any geodata, the dialog for choosing a coordinate system should pop up. Just input the EPSG code or the name of the desired CRS, choose it from the list of results, and click on the "SET" button to save your choice.
MapTiler Engine also allows to load the CRS from an external file or to specify it manually.
Loading the CRS from a file
To load the CRS from a file, click on the "Modify or load from file" option from the "Coordinates" menu and navigate to the file in the file dialog. Typically used extensions are: .prj, .srs, .txt.
Searching for the SRS manually
To open the coordinate system search dialog, click on the "Find coordinate systems" option from the "Coordinates" menu.
MapTiler Engine allows you to search for a country, the code of the coordinate system, or its name. For instance, search for "United Kingdom" to get the coordinate systems used in this area. Also, other keywords such as "Britain" or the "Ordnance survey" will guide you to choose the right coordinate system for your map.
For each coordinate system, there is also a list of different variants that differ with the accuracy of the projection. You can find it by clicking on the little arrow next to the coordinate system name.
After you find the right coordinate system for your map, click on the "SET" button.
MapTiler Engine supports over 6 thousand coordinate systems from all over the world by using the EPSG.io database.
Defining a custom CRS in MapTiler Engine
In case the desired coordinate reference system is not found in the EPSG.io database, you can add a custom CRS definition to MapTiler Engine. In order to do so, perform the following steps:
Go to a coordinate system registry (you can use this one)
- Search for the desired CRS
Copy the WKT definition of the CRS (note: It has to be WKT version 1)
In order to add the obtained WKT to MapTiler Engine, go to the "Find coordinate systems" dialog, click on the "Details" button, remove the text from the bottom text field, paste the copied WKT definition, and click on the "SET" button. Now, the label "Coordinates" combo box should show "Undefined/Custom". That's it, now your map should be rendered using the custom CRS of your choice.
Setting the geolocation
After setting the desired CRS, you can proceed with adding/modifying the geolocation of your data. There is a separate article on how to do this.