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qgis2web is a plugin for QGIS which creates webmaps. This question is about its OpenLayers 3 export. It exports QGIS layers to geoJSON to pull into the OL3 map. It writes them in EPSG:4326, as I believe this is at least a proposed standard for geoJSON. This works for default (EPSG:3857) OL3 maps.

However, I am trying to implement support for multiple projections in qgis2web. I cannot get the geoJSON EPSG:4326 points to display on the OL3 map if it uses any projection other than EPSG:3857.

A sample qgis2web OL3 map is here: https://www.dropbox.com/s/76ru3x1b6mvjpc3/epsg_27700.zip?dl=0. Can anyone help me figure this out? What am I missing?

  • Could you please post the html code that was generated by qgis2web? – Alexis_A Dec 7 '15 at 18:31
  • It's the Dropbox zip. The output is structured in several files and folders. However, I'll try to pull out the relevant bits and paste them in. – Tom Chadwin Dec 7 '15 at 19:05
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I didn't investigate all, but changing scripts loading order is already better: something is now visible.

I just replaced

<script src="./resources/ol.js"></script>
<script src="http://cdnjs.cloudflare.com/ajax/libs/proj4js/2.3.6/proj4.js"></script>

with

<script src="http://cdnjs.cloudflare.com/ajax/libs/proj4js/2.3.6/proj4.js"></script>
<script type="text/javascript">
  proj4.defs('EPSG:27700','+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +ellps=airy +towgs84=446.448,-125.157,542.06,0.15,0.247,0.842,-20.489 +units=m +no_defs');
</script>
<script src="./resources/ol.js"></script>

It seems you missed that you need to load proj4js, then declare projections before any OpenLayers script whereas you were already calling your custom projection before declaring it.

  • +1 exacly the same and standardize relative path: ="./*" or delete all ./ – GeoStoneMarten Dec 7 '15 at 19:22
  • Completely correct, and splendidly simple. Thanks very much @ThomasG77. – Tom Chadwin Dec 7 '15 at 19:34
  • Code is inherited from multiple authors @GeoStoneMarten, so standardization is definitely not complete - point taken. – Tom Chadwin Dec 7 '15 at 19:35
  • @TomChadwin no problem. This is just an information to get clean code – GeoStoneMarten Dec 7 '15 at 19:51

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