Hi Bill, I would also recommend what Randy suggests. Just multiply the y-axis with -1. This way you won't have problems with text.
Using geographic coordinates works fine within a certain range. I found out that some or most have limitations in the coordinate range. I have most problems with Mozilla. If I use realworld coordinates (say in swiss coordinate system, with a range between 450000 to 850000 in x and 70000 to 300000 in y) I had problems when zooming in to larger map scales. This is a problem I only experienced with Mozilla. This map worked fine in Opera 9, ASV and Batik. I hope that the mozilla team will one day improve their valid coordinate ranges. Likewise I had problems when using geographic coordinates in ASV and zooming in very far. Funny things happened: e.g. paths would render fine, but rects or markers would render with an offset. So, to be on the safe side one should transform the coordinates to a smaller range. Andreas --- In [email protected], Bill Thoen <[EMAIL PROTECTED]> wrote: > > > I've recently gotten re-interested in SVG mapping after experimenting with > Firefox 1.5's built-in SVG support, but I've always found fitting map > coordinates to the SVG system (x-coordinates increases from left to right > and y-coordinates increase from top to bottom) to be somewhat problematic. > What do people think is the best way to transform coordinates from > real-world to SVG? > > Do you convert geographic coordinates to local coordinates (like screen > pixels or twips, etc. where the Y-coordinate increase to the south), or do > you keep the geographic units unchanged but just reverse the y-axis by > multiplying by -1, or do you perform a local transform on the y-axis so > that you can use the unmodified geographic coordinates in SVG directly, or > what? > > The choice impacts things like coordinate tracking or text placement, and > other features that you may want to support in an online map presentation. > I also wonder about issues like whether it's more efficient with GML paths > to compress floating point coordinates to integers. Looking around the > 'net, I see examples of all sorts of coordinate-transforming techniques in > SVG maps, so is there any consensus on the "best" method, and why? > > So does anyone here have any opinions about the pros and cons of the > various ways people convert geographic coordinates into SVG coordinates? > > - Bill Thoen > ----- To unsubscribe send a message to: [EMAIL PROTECTED] -or- visit http://groups.yahoo.com/group/svg-developers and click "edit my membership" ---- Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/svg-developers/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
