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Handling GeoJSON Files with Unspecified Projected Coordinate Systems

In the latest GeoJSON specification (2016), the coordinate reference system for all coordinates is a geographic coordinate reference system—using the World Geodetic System 1984 (WGS 84) datum—with longitude and latitude units of decimal degrees. The previous specification (2008) allowed for the use of alternative coordinates systems, but this was removed because of interoperability issues.

MAPublisher still recognizes GeoJSON files with a specified coordinate system even though it is no longer officially supported. However, if no coordinate system is specified, MAPublisher will assume the coordinates are in WGS 84. Occasionally, this may cause a problem of improperly formatted files that contain projected coordinates but have no specified coordinate system. In this case, users will need to either choose a coordinate system during import or modify the GeoJSON file by adding a coordinate reference system (CRS) object manually.

Selecting a Coordinate System on Import

To change the coordinate system using the Import dialog box, click Advanced and select the WGS 84 link under Coordinate System. Ignore the warning about changing the coordinate system by clicking “Replace coordinate system”. Select the correct projected coordinate system from the list.

 

Modifying the GeoJSON File Manually

Coordinate reference systems can be specified in a GeoJSON file using a CRS object. You can view the contents of any GeoJSON file by opening it in a text editor such as Notepad. Copy and paste the text below after the line: “type”: “FeatureCollection”, (usually on line 2). Change the EPSG number to the correct CRS for your dataset. See Spatialreference.org to lookup an EPSG code.

"crs":
{
   "type" : "name",
   "properties" :
   {
      "name" : "EPSG:[EPSG Code]"
   }
},

Example:

The GeoJSON file can now be read properly by MAPublisher and can be imported as normal.


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