Hi all, I'm trying to get my head around vertical and 3D coordinate reference systems. Not being from a GIS background, I'm not too familiar with how CRSs are constructed. I'm looking for a way to represent oceanographic and meteorological measurements, which are typically captured as longitude,latitude,height (or depth). These heights are sometimes relative to the geoid, and sometimes relative to the ellipsoid (presumed to be WGS84). As a further complication, numerical models are often run on a spherical earth, so "height" in this case is relative to a spherical datum. (I'm not even going to mention - for the moment - things that are measured relative to instantaneous sea surface...)
I was interested by this statement in the javadoc for DefaultVerticalCRS: "ellipsoidal heights (h) cannot be captured in a vertical coordinate reference system. Ellipsoidal heights cannot exist independently, but only as inseparable part of a 3D coordinate tuple defined in a geographic 3D coordinate reference system." However, the DefaultVerticalCRS class itself has the ELLIPSOIDAL_HEIGHT property (a 1D vertical CRS), which would seem to contradict this statement. Should the ELLIPSOIDAL_HEIGHT CRS be used with caution? Is it an approximation? On a related note, is DefaultGeographicCRS.WGS84_3D an inseparable 3D CRS? Or is it a combination of WGS84 + ELLIPSOIDAL_HEIGHT? In other words, is the interpretation of the ellipsoidal height dependent upon latitude and longitude? Or are all three axes orthogonal? (BTW does anyone know of any good CRS primers?) Thanks in advance, Jon -- -------------------------------------------------------------- Dr Jon Blower Tel: +44 118 378 5213 (direct line) Technical Director Tel: +44 118 378 8741 (ESSC) Reading e-Science Centre Fax: +44 118 378 6413 ESSC Email: [EMAIL PROTECTED] University of Reading 3 Earley Gate Reading RG6 6AL, UK -------------------------------------------------------------- ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Geotools-gt2-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users
