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

[Jody Garnett <jody.garnett@xxxxxxxxx>]

Heh I had better luck going to google maps and zooming out inorder to
see the different shape they produce for the uk.

Jody

On Tue, Nov 23, 2010 at 2:36 AM, Jody Garnett <jody.garnett@xxxxxxxxx> wrote:
> 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
>>
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>