[MetaCRS] Translation WGS84 to Mercator

[Косолапов Глеб]

Mikael, thank you so much! 
It works!

Gleb.

30.11.2010, 13:26, "Mikael Rittri" <Mikael.Rittri at carmenta.com>:
> Hello Gleb,
>
> According to http://spatialreference.org/ref/epsg/3395/proj4js , the
> definition of EPSG:3395 (WGS84 / World Mercator) in proj4js is
>
> +proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
>
> If you instead use
>
> +proj=merc +lon_0=90 +k=1 +x_0=10018754.171395 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
>
> you should get a Mercator with projected coordinates that are centered on longitude 90E,
> so they are interrupted along the meridan 90W, far from Russia, instead of meridian 180E.
>
> The value for x_0 is a quarter of the WGS84 equator in meters, which is the easting value for
> meridian 90E in EPSG:3395.  This means that the coordinates in this recentered projection
> agree with EPSG:3395 from 90W and east to 180E.  (But between 180E and further east
> to 90W, the eastings are 40075016.685578 m larger, which is what you need to get continuity
> over meridian 180E.)
>
> I haven't tested this behaviour with proj4js, but it works with the Proj.4 of FWTools:
>
>> proj +proj=merc +lon_0=90 +k=1 +x_0=10018754.171395 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
>
> 190 0
> 21150703.25     0.00
>
> Best regards,
> Mikael Rittri
> Carmenta
> Sweden
> http://www.carmenta.com
>
> -----Original Message-----
> From: metacrs-bounces at lists.osgeo.org [mailto:metacrs-bounces at lists.osgeo.org] On Behalf Of Kosolapov Gleb
> Sent: den 23 november 2010 09:55
> To: metacrs at lists.osgeo.org
> Subject: [MetaCRS] Translation WGS84 to Mercator
>
> Hi, everyone from Russia!
>
> I'm using proj4js with OpenLaerys.
> I must translate WGS84 to Mercator (EPSG:3395, for example).
> My country lies through 180th meridian (antimeridian). So, in WGS84 this territory ends near 190 longitude. And everything works fine.
> But when I transform 190 lat to Mercator, I get negative value -18924313.434856504. That's very bad for every operation with Mercator coordinates in OpenLayers.
>
> Please, help me how to transform 190 lat to positive Mercator using proj4js...
>
> Regards, Gleb.
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