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Re: svg comment - coordinates

From: Jon Ferraiolo <jferraio@Adobe.COM>
Date: Tue, 23 Feb 1999 10:44:22 -0800
Message-Id: <199902231841.KAA12467@mail-345.corp.Adobe.COM>
To: "Michael Gould" <gould@inf.uji.es>
Cc: <www-svg@w3.org>
At 06:56 PM 2/23/99 +0100, Michael Gould wrote:
>Hello.
>
>Those of us who work with geographic information --and hope to view our maps
>in SVG-- would like to suggest explicit treatment of real-world coords,
>within chapter 8 of the working draft. We'd like to see the ability to
>transform outside the CSS realm (points, mm, inches) to metres, kilometres
>etc. This allows users to do things like measure real-world distances
>on-screen (for example, click on origin and destination on a SVG map, and
>get the crow's-flight distance), calculate polygon areas...
>
>Maybe real-world coords, units etc. are in there somewhere, but it's not
>obvious reading over the current SVG draft.

You can set up you own coordinate system using the 'transform' property.
There are lots of options to this property. One way to use it would be to
send down coordinates in whatever units you want (e.g., metres and
kilometres) and then use 'transform: fit(bboxleft bboxtop bboxright
bboxbottom)', where the bbox values indicate the bounding box of the map in
your coordinate system.

Regarding measuring real-world distances by clicking on the screen, you
could calculate that by scaling the screen units by
(bboxright-bboxleft)/<width>, where <width> is the width of the box into
which the map is drawn, measured in pixels (assuming uniform transformations).


Jon Ferraiolo
Adobe Systems Incorporated
Member of SVG working group
Received on Tuesday, 23 February 1999 13:42:36 GMT

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