Martin, Thank you! The light bulb just went on!
Without realizing it, when I asked the question, I was "thinking JavaScript". But, hey, my HTML is being served up from a Java based server, where I have access to GeodeticCalculator. That sure makes life easier. Thanks again, Todd --- Martin Desruisseaux <[EMAIL PROTECTED]> wrote: > todd runstein a écrit : > > Suppose I'm using EPSG:4326, and I have the two > > coordinates -122:40 and -120:42. It would seem > > reasonable that because -122-(-120)=-2 and > 40-(42)=-2, > > I have a proper square (something that would fit > > nicely in a 500px X 500px window). Following this > > logic, -122:40 and -120:43 would fit in a 500px X > > 750px window. > > It would appears as a square if two conditions are > meet: > > * The underlying coordinate system is cartesian. > * All axis use the same units of measure. > > Those conditions are often true for a projected CRS. > But EPSG:4326 is a > geographic ones, and all geographic CRS use an > ellipsoidal CRS. Whatever > such shape in a geographic CRS appears like a square > or not is renderer > dependent. It depends if the renderer performs > on-the-fly reprojection > in order to take in account the flat shape of the > screen, or if it just > display the shape "as is" without any processing. In > the later case the > shape will appears as a square, but you should > generally not rely on that. > > Note that for any computation of geometric > properties like distance, > area, angle, etc., you should definitively not > assume that the shape is > square and not rely on euclidian formulas for > geographic CRS. > > Martin. > The only "dumb question" is the one you were too afraid to ask. ________________________________________ Check out RouteRuler - Free software for runners, cyclists, walkers, etc. http://routeruler.sourceforge.net ________________________________________ Get a handle on your data with "pocOLAP", the "little" OLAP project http://pocolap.sourceforge.net ________________________________________ __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click _______________________________________________ Geotools-gt2-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users
