[gdal-dev] Need some help with projections

[Paul Meems]

Thanks Jean-Claude,

I was using EPSG:900913 for the OSM tiles and Googled about it looking for
the +towgs84 parameter but couldn't find anything.
I did find several posts about EPSG:3785 being the same as EPSG:900913 and
that one does have the +towgs84 parameter.
Should I use that proj4 string instead?
+proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +a=6378137 +b=6378137
+towgs84=0,0,0,0,0,0,0 +units=m +no_defs

And how about the custom projection? Do you have any idea how to create a
proj4 style string from that?

Thanks,
Paul


2010/7/14 Jean-Claude REPETTO <jrepetto at free.fr>

> Hi,
>
>
> On 07/14/10 11:54, Paul Meems wrote:
>
>>
>> I'm using this proj4 string for the OSM tiles:
>> +proj=merc +lon_0=0 +lat_ts=0 +x_0=0 +y_0=0 +a=6378137 +b=6378137
>> +units=m +no_defs
>>
>>
> This one is not correct if you want to do a datum transformation : the
> +towgs84 parameter is missing.
>
> Jean-Claude
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