Andre, That was one golden nugget piece of information you gave me about SVG with regard to scales. I have a lot better understanding about viewbox and scale within SVG. I will now look into displaying graphical scales instead of numerical scales in my application.
Thanks a lot for your time and insight, Kiran --- In [EMAIL PROTECTED], "andr� m. winter" <[EMAIL PROTECTED]> wrote: > 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: svg-developers- [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. Get it for free! http://us.click.yahoo.com/L5YrjA/eSIIAA/yQLSAA/1U_rlB/TM --------------------------------------------------------------------~-> ----- 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/
