Difference between Profile : global-mercator and UTM

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Rahul Jain Rahul Jain
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Difference between Profile : global-mercator and UTM

Hi Guys,

Is global-mercator and UTM are one and same thing ? If not what is the difference ?

Kind regards
Rahul
gwaldron gwaldron
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Re: Difference between Profile : global-mercator and UTM

Rahul,

They are not the same. Mercator and UTM are 2 different map projections:

Mercator is the projection used by most of the online mapping providers (Google, Yahoo, Microsoft, OpenStreetMap) for global maps, because it maintains a good visual proportionality that lends itself well to 2D maps.

UTM is not one but a series of map projections, each of which represents one 6-degree slice of the Earth (a "zone"). A UTM zone gives you better accuracy in smaller areas, but you can only represent one zone at a time.
Glenn Waldron / Pelican Mapping
Rahul Jain Rahul Jain
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Re: Difference between Profile : global-mercator and UTM

Thanks Glenn,

How can we convert a point selected on a map in global mercator in to corresponding lat long ?

Kind Regards
Rahul
gwaldron gwaldron
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Re: Difference between Profile : global-mercator and UTM

You can use its SpatialReference (SRS) class like so:

osg::ref_ptr<SpatialReference> merc = SpatialReference::create( "spherical-mercator" );
SpatialReference* latlon = merc->getGeographicSRS();
merc->transform( merc_x, merc_y, latlon, out_lon, out_lat );

You can also create the "merc" SRS object from your terrain's CoordinateSystemNode:

osg::ref_ptr<SpatialReference> merc = SpatialReference::create( csnode->getCoordinateSystem() );
Glenn Waldron / Pelican Mapping
Rahul Jain Rahul Jain
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Re: Difference between Profile : global-mercator and UTM

Hi Glenn,

Thank you very much. One last question :) Is the top node loaded by earth file, is a coordinate System node like the node created by osgdem or VPB

kind regards
Rahul
jasonbeverage jasonbeverage
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Re: Difference between Profile : global-mercator and UTM

Hi Rahul,

The top of of an earth file is actually now a "Map" node, which contains a CoordinateSystemNode as a child.  You can use  a NodeVisitor to find the CoordinateSystemsNode if you need access to it.

Thanks!

Jason

On Wed, May 6, 2009 at 2:26 PM, Rahul Jain (via Nabble) - No Reply <[hidden email]> wrote:
Hi Glenn,

Thank you very much. One last question :) Is the top node loaded by earth file, is a coordinate System node like the node created by osgdem or VPB

kind regards
Rahul


View message @ http://n2.nabble.com/Difference-between-Profile-%3A-global-mercator-and-UTM-tp2809356p2822937.html
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