[HOT] Hot export : coordinate systeme

Andy Anderson aanderson at amherst.edu
Fri Oct 17 18:40:43 UTC 2014

GeoJSON and Shapefile are two different formats for structuring spatial coordinate data; KML and GPX are also common. Those coordinates can be in any well-known coordinate reference system (CRS) such as WGS84 or Spherical Mercator.

In the case of GeoJSON, commonly used by web-mapping applications, if the CRS is not explicit it is by default taken to be WGS84 (see http://geojson.org/geojson-spec.html#coordinate-reference-system-objects ).

In the case of shapefiles, commonly used by desktop mapping programs, at least ArcGIS assumes the coordinate data is in the same CRS as the current map view (data frame).

The sensible default CRS would be WGS84. People in the field using an older GPS device might need shapefiles, which until a few years ago was the lingua franca, but the software I and many others use, DNRGPS, now understands  all of these formats ( http://maps1.dnr.state.mn.us/dnrgps/file_types.html ).

— Andy Anderson

On Oct 17, 2014, at 4:46 AM, Fran Boon <francisboon at gmail.com> wrote:

> On 17 October 2014 07:46, Fred Moine <frmoine at gmail.com> wrote:
>> Let see why it has been coded like that, but for esri users (most of the gis
>> officer working in humanitarian are using Arcgis, for now) it could be
>> interesting to have EPSG: 4326 like in Geofabrik  website.
> Not just ESRI users, Sahana users also.
> I can see why GeoJSON might be in Spherical Mercator by default, but
> Shapefile is bizarre
> Allowing users to select the projection will be ideal, but we'll still
> want a sensible default both for those users who do this all the time
> (1 less click) & those who don't read/understand properly ;)
> F
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