Hello!! Take a look at this email, from the PostGIS mailing list: http://www.nabble.com/function-to-find-UTM-zone-SRID-from-POINT-tf669268.html#a1772300
Hope this help Leandro 2007/10/26, Barend Köbben <[EMAIL PROTECTED]>: > > Hi Linda, > > I think your question starts with a basic mis-assumption: > > > Basically if I pass in the x,y coordinates in WGS_84 or any other meter > > projection > > WGS84 is a officially a Datum, not a projection. A Datum is a global or > ellipsoidal object closely matching the Earth's shape. A projection is > literaly what it says: a projection of that global object on a flat > surface. > > (for a good overview, I suggest http://kartoweb.itc.nl/geometrics/) > > What most people mean if they say "WGS84 projection" is "Geographic > coordinates (in latitude, longitude) on the WGS_84 Datum". Therefore it's > coordinates are NOT x,y but lat,lon and it's NOT a meter projection but a > (decimal) degrees description of a vector to a point on the surface of a > global object (actually the lat and lon are angles with respect to the > globe's origin...). > In more simpel terms: lat,lon does not have a cartesian grid with an > origin > and equal values along two axes as its mathematical basis, as the UTM and > other (meter) projections have. > > > I would like it to return the zone that those coordinates are in. > You can easily do that if indeed you have lat,lon coordinates as described > above. As the zones of UTM are just 60 zones divided over the 360 degrees > of > longitude, each zone is 360/60=6 degrees of longitude. Zone 1 is from -180 > to 174, zone 31 is from 0 (Greenwich) to 6, etcetera. The zones each have > a > N-S divide over the equator, so if the latitude is positive, the zone is > zone xN, if negative it's zone xS. > So my city Enschede is at lat,lon= 52.2166667 , 6.9 and therefore in zone > 31N. > > For "any other meter projection" it's not so easy, because the projections > all use different origins of their grid. The best is to calculate the > projected x,y back to lat,lon on the WGS84 (in PROJ4-based systems use the > toWGS84 part of the projection description) and then to the UTM zone... > > Yours, > __ > Barend Köbben > International Institute for Geo-information > Sciences and Earth Observation (ITC) > PO Box 6, 7500AA Enschede (The Netherlands) > ph: +31 (0)53 4874253; fax: +31 (0)53 4874335 > > > > > _______________________________________________ > Users mailing list > [email protected] > http://openlayers.org/mailman/listinfo/users >
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