[OSM-dev] openstreetmap, openlayers and overlays

[Artem Pavlenko]

Hi Richard,

On 5 Jul 2007, at 09:55, Richard Duivenvoorde wrote:

> Hi List,
> I've an OpenLayers page, on which I show the OpenStreetmap (using  
> source
> of www.openstreetmap.org).
>
> I downloaded form geonames.org some points and stuffed them in Postgis
> (latlon: 4326). I then used Postgis transform to reproject those  
> points
> to 51001 / 41001 (aka using proj string:
> <41001> +proj=merc +lat_ts=0 +lon_0=0 +k=1.000000 +x_0=0 +y_0=0
> +ellps=WGS84 +datum=WGS84 +units=m +no_defs  no_defs <>
> )
>
> Showing those points as overlay on a googlemap seems fine:
> http://www.duif.net/GoogleGeonames.jpg
> But putting them on OSM they seem shifted (or map is shifted?):
> http://www.duif.net/OpenStreetsGeonames.jpg
> (the big dot in the middle are supposed to be in the city of  
> Amsterdam)
>

Hmm... both OpenStreetMap and Google are using the same tile schema.  
You can see this on : http://media.mapnik.org/oxford-osm.html (just  
pan/zoom to Amsterdam) and they overlap correctly.

I suspect OL is doing something different for TMS and Google layers.  
You can try exporting KML from postgis and overlay it  on top of OSM,  
using GMap interface. If that works you should post to OL list.

Cheers
Artem


> My question:
> - do I do something stupid here?
>
> - does anybody else succeeded in putting custom (latlon) points as
> overlay on openstreetmap?
>
> - has somebody some viable explanation for the shift? (at this  
> moment I
> cannot put this stuff on the live server, but if neccessary I will  
> do that).
>
> TIA
>
> Richard
>
> ps if you think this questions belong on the userlist: let me know, I
> just thought here was more interest and knowledge about these kind  
> of stuff
>
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> http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/dev
>

Artem Pavlenko
http://mapnik.org



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