Allright, the platte carré projection is what i had to know! Thanks! grtz, Wouter Schaubroeck
On Wed, Jun 25, 2008 at 9:49 AM, Adrian Custer <[EMAIL PROTECTED]> wrote: > On Tue, 2008-06-24 at 16:56 +0200, Wouter Schaubroeck wrote: >> Hey List, >> >> I have the following question: what kind of projection method does >> geotools use, to create images of data? Especially if the data is in >> wgs84, and the resulting image is also asked in wgs84. Or am i missing >> something here? > > Hey, > > Not knowing your level of knowledge, I'll answer at the risk of stating > the obvious. WGS84 uses a geographic coordinate system, something > necessarily defined in a 'globular' mathematical space (a closed, > finite, unbounded manifold), therefore which cannot possibly be drawn on > a flat screen without some kind of alteration, called a projection. So > if you see WGS84 data on a flat surface, they have been projected and > are no longer in 'WGS84'---the real question is what projection is > used. > > If no specific projection has been defined, most modern tools > unfortunately fall back on the mindless projection, often formally > called "platte carré", where the long, lat values of WGS84 simply become > X,Y on the surface. You can recognize the shape of the world in this > projection since it is everywhere. Greenland, as is often the case, can > serve as a visual check on the distortion of this projection. > > Google says: > http://www.mapresources.com/results.asp?txtkeys=platte > +carre&name=Platte%20Carre%20World > > > Projections can be done with more care so as to preserve certain > characteristics from the original data (while sacrificing others). > Platte carré does not preserve any characteristics of interest, whereas > other projections preserve shape locally, direction from a particular > position of origin, OR relative areas, but not all at once. Hence, those > who are projecting data rather than images generally use formal > projections, area preserving, line preserving, or shape preserving > according to their needs. > > Hope that helps, > --adrian > > > >> I know that it's possible to ask the images in >> cartographic projections (ex lambert 72), but what happens if this >> isn't the case? >> >> thx!! >> Wouter Schaubroeck >> >> Geo Solutions > > -- Woody Allen - "I am not afraid of death, I just don't want to be there when it happens." ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php _______________________________________________ Geotools-gt2-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users
