I have GPS coordinate data in pure decimal GPS coordinate format for
example 25.124167 in order to place the feature on the map. And I will
use Google Maps layer with OpenLayers. Is any convertion required? Does
OpenLayers implement in the background?
You will do coordinate conversion, yes. The map will use the Web
Mercator SRS -- to place a marker using WGS84, you would need to convert:
var SRS_GOOGLE = new OpenLayers.Projection("EPSG:900913");
var SRS_LONLAT = new OpenLayers.Projection("EPSG:4326");
var center = new OpenLayers.LonLat(-85.5678, 45.12345);
center.transform(SRS_LONLAT,SRS_GOOGLE);
map.setCenter(center, 10);
var box = new OpenLayers.Bounds(-122,43,-121,44);
box.transform(SRS_LONLAT,SRS_GOOGLE);
map.zoomToBounds(box);
If you forget to do this transform, then your coordinates will be very
close to the 0,0 mark at the equator & the Greenwich meridian (-85 and
45, in meters from 0,0). That's a great debugging tip: if your marker is
appearing at "practically 0,0" you probably are using "very tiny
coordinates" for your SRS.
--
Greg Allensworth, Web GIS Developer
BS A+ Network+ Security+ Linux+ Server+
GreenInfo Network - Information and Mapping in the Public Interest
564 Market Street, Suite 510 San Francisco CA 94104
PH: 415-979-0343 x302 FX: 415-979-0371 email: [email protected]
Web: www.GreenInfo.org www.MapsPortal.org
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