Re: [udig-users] Why does WGS84 map of UK appears squashed in uDig?

[Jody Garnett <jody.garnett@xxxxxxxxx>]

I was under the impression that google uses their own projection that
distorts things more as you get near the poles. As far as I know WGS84
is being displayed correctly :-)

If you like you can try the google projection in udig; It was given an
informal number of "EPSG:900913" although I understand it has been
blessed with an offical number by EPSG now.

here is a reference:
- http://spatialreference.org/ref/epsg/4326/
- http://spatialreference.org/ref/sr-org/6627/

If you compare the two you will see they are different shapes.

Jody


On Thu, Nov 4, 2010 at 8:14 PM, Andrew Ellis <Andrew.Ellis2@xxxxxxxxx> wrote:
>
> Hi,
>
> I am a newbie to GIS and uDig and I have a shape file dataset for
> regions of the UK, which I understand is in OSGB36 coordinates.
>
> When I load this shapefile directly into uDig with
> Layer->Add->Files->shapefile.shp, it appears the way you would expect to
> see an outline of the UK, say, on Google Maps, for example.
>
> However the coordinates in the shapefile are in OSGB36 format (metres
> from a point in the south west) so for the coordinates to tally up with
> Google Maps/Google Earth in KML, they need to be converted to WGS84
> format.
>
> I seem to have done this successfully with the following transformation
> of the original shapefile with FWTools and the following command:
>
> ogr2ogr -t_srs EPSG:4326 -s_srs "+proj=tmerc +lat_0=49 +lon_0=-2
> +k=0.9996012717 +x_0=400000 +y_0=-100000 +ellps=airy +datum=OSGB36
> +units=m +no_defs" regions_wgs84.shp shapefile.shp
>
> Now the coordinates in regions_wgs84.shp match up with Google Maps and
> can be used in KML. So for example, if I load in the new shapefile into
> uDig and overlay a point in a new layer using coordinates for a place
> taken from Google Maps, it appears in the correct place on the rendered
> map in uDig.
>
> However, I am perplexed about the map appearing vertically squashed in
> uDig, whereas in Google Maps the map appears as you would expect it.
>
> What am I doing wrong or not doing, so that the shape files transformed
> to WGS84 coordinates appear correctly in uDig with the correct WGS84
> coordinates?
>
> I have also tried loading the transformed shape file into Postgres with
> the following,
>
> shp2pgsql -D -s 4326 regions_wgs84.shp regions > regions.sql
> psql -Upostgres -f regions.sql db
>
> , and then loading them into uDig via Layer->Add->PostGIS and selecting
> the table from the database and the same squashed map appears.
>
> Any help would be much apprectiated!
>
> Thanks,
>
> Andrew
>
> http://www.bbc.co.uk/
> This e-mail (and any attachments) is confidential and may contain personal views which are not the views of the BBC unless specifically stated.
> If you have received it in error, please delete it from your system.
> Do not use, copy or disclose the information in any way nor act in reliance on it and notify the sender immediately.
> Please note that the BBC monitors e-mails sent or received.
> Further communication will signify your consent to this.
>
> _______________________________________________
> udig-users mailing list
> udig-users@xxxxxxxxxxxxxxxxxxxxx
> http://lists.refractions.net/mailman/listinfo/udig-users
>