Transforming ViennaGIS to WGS84 coordinates

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1 min read

Recently I had to transform ViennaGIS Gauß-Krüger M 34 MGI Austria GK East coordinates to Google WGS84 using EPSG code 31256. The use case was to show pins on Google Maps or Leaflet of ViennaGIS provided objects and locations.

ViennaGIS map

Unfortunately ViennaGIS (https://www.wien.gv.at/viennagis/) uses a Gauß-Krüger M 34 projection which cannot be used with most other map SDKs. So I had to transform the coordinates to Google’s coordinate system beforehand. I used proj4j (https://github.com/locationtech/proj4j) and proj4js (https://github.com/proj4js/proj4js) libraries which are ports for Java and JavaScript of the proj library (https://proj.org/). Following code shows how to transform ViennaGIS GK34 to WGS84 with Kotlin or JavaScript:

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