hi
currentScale equals 1 onload of your svg document. with following parameters 1) viewBox width and height values 2) width/height in pixel of your viewport 3) preserveAspectRatio attribute you are able to calculate a map scale. point 2 and 3 are related as preserveAspectRatio says the viewer how to fit the drawing into the available viewport, thus initial map units may vary. the onzoom event triggers zoom changes and thus gives you a new currentScale that you can retransform into a map scale. this stays true as long as you do not: a) modify viewBox b) change window/frame extents where the svg is displayed because on (a) scale reverts to 1 and you have to reiterate the initial ratio getting. on (b) things get much more complicated as viewer do zoom AND translate. concerning map scales on screens there is another "don't": you cannot show up a numerical scale value as most GIS-export tools do (one example between much others <http://www.uismedia.de/mapview/beispiele/schlatterbach/index.html>). the reason is very simply demonstrated: show the identical map interface with numerical scale on your laptop (~15") AND a video projector (somthing around 4 meters digonal. but the numerical scale is the same on both displays. cartographical nonsense. the foolish fact here is that most GIS do display numerical scales in their interfaces without warning about the errors here. the same happens between different classical screens (at a lower level). the reason are differences in pixel size on displays and the fact that you CANNOT evaluate pixel size with client side scripting. the consequence: you can only show a graphical scale unless you ask the user to communicate a screen size in natural units. see <http://tirolatlas.uibk.ac.at/maps/thematic/index.html?lang=it&menu=36>, long load time, IE only. on the left you have "scale" and "optioni". go on "optioni" and enter different visible screen widths (change again with "all'ampiezza dello schermo"). you will see a nummerical scale appear in the graphcial scale bar and that only slight width changes have big consequences in nummerical scale. andr� kbatchu schrieb: > Andre, > > Thanks for your reply. That answers my question about the > relationship between 'viewbox' attributes and 'scale'. What would be > the steps (using CurrentScale/Translate) to zoom in to the selected > property extent and display the corresponding scale? > > Thanks > Kiran > > --- In [EMAIL PROTECTED], "Andr� M. Winter" > <[EMAIL PROTECTED]> wrote: > >>hi, >> >>scale doesn't change after viewBox changes because the scale is >>reinitated on viewBox updated. thus it stays or reverts to 1. >> >>don't mix viewBox handling and currentScale/Translate. both have > > their > >>advantages but switching results in undesired results as you have > > seen. > >>andr� >> >> >> >>>Hello all, >>> >>>I am using SVG to create a mapping application. I have a dropdown >>>list of some properties within a city. When a user clicks on any > > one > >>>from this list, the map zooms to that particular property. To > > zoom > >>>to that property and fit it entirely in the viewport, the only > > thing > >>>I do is set the viewbox attributes (x,y,width,height) equal to > > the > >>>extent of that property. This works fine but my problem lies >>>with 'scale'. After the property is displayed, I also would like > > to > >>>display the 'scale' at which it is being displayed. But when i > > try > >>>to read the scale (after zooming), the scale still shows the >>>original scale (before zooming). Why is the 'scale' not being >>>changed ? Doesnt changing the 'viewbox' attributes automatically >>>change the scale? How do i find the 'current' scale after the >>>property is zoomed in? >>> >>>Thanks for your help, >>>Kiran >>> > > > > > > ----- > 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 > > > > > > > -- ___________________________________________________________________ _________ _/ \____ _______ _/ ___-----___ \_____/ _ \ / _/ \|/ \_ \_,+' \ \ / / _\| |/_ \ | | ,----------------------------------------- � � � |==THERE'SSOMANYDIFFERENTWORLDSSOMANYDIFFERENTSUN================ |==SANDWEHAVEJUSTONEWORLDBUTWELIVEINDIFFERENTONES================ | '----------------------------------------- � � � \ \_ -/| |\-_/ _ | \_ \___ /|\ ___/ _____ / '+,_/ / \_ ----- ____/ \_______/ \_________/ andre m. winter <http://www.carto.net/> ------------------------ Yahoo! Groups Sponsor --------------------~--> Make a clean sweep of pop-up ads. Yahoo! Companion Toolbar. Now with Pop-Up Blocker. 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