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

["Andrew Ellis" <Andrew.Ellis2@xxxxxxxxx>]

Thanks Jody. Yes a colleague pointed out that Greenland is nearly the
size of Africa on Google maps! 
I understand now that the uDig WGS84 rendering is the unprojected view
of the UK and that Google maps (including the satellite view) reprojects
the data so Britain appears elongated.
Am I right in saying, if you were to view Britain and Ireland from space
it would appear with the same shape as in the WGS84 uDig rendering?
Andrew

-----Original Message-----
From: Jody Garnett [mailto:jody.garnett@xxxxxxxxx] 
Sent: 22 November 2010 16:38
To: Andrew Ellis
Cc: udig-users@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: [udig-users] Why does WGS84 map of UK appears squashed in
uDig?

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

>> Layer->Add->Files->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
>>
>

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.