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| GeoCommunity Mailing List |
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| Mailing List Archives |
| Subject: | Re: [gislist] Coordinate systems in SVG maps |
| Date: |
04/09/2006 09:05:01 PM |
| From: |
nyem |
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Bill,
The questions are best posted to svg-developers@yahoogroups.com, or you
can check http://www.carto.net/ or http://www.svgx.org/learning.html for
comprehensive svg-mapping resources.
My method is to place map objects within a group that is flipped
<g transform="scale(1,-1)">
and reverse the scale for text objects
<text x="0" y="0"
transform="translate(102.924000,1.840570) scale(1,-1)">
My Label
</text>
The difficult part would be to track the coordinates between the map,
the svg viewbox and the screen, but once you understood the coordinate
system (see http://www.perfectxml.com/LearnSVG.asp) you can go very far.
There are many ways to do it, choose the one that works best for you.
Good luck,
- nyem
Bill Thoen wrote:
> I've recently gotten re-interested in Scalable Vector Graphics (SVG) maps
> 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 do you 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 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?
>
> Does anyone here have any experience with this SVG mapping topic and have
> you an opinion?
>
> - Bill Thoen
>
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