Hi Jacky,
if you change the map extent by panning or zooming, the whole geometry is removed and replaced by the new geometry - with the current approach. I know, it is not very elegant, but easier to implement. The current approach does not query the difference of two overlapping map extents. It would probably be easy to calculate the intersection of the previous map extent and the current map extent for panning (if the two overlap at all), but it is definitely more complex for zooming. Also you would have to introduce some session management or would have to transfer the previous map extent with the URL request as well. You are welcome to enhance my example and post it for discussion. I'd love to improve the tutorial and my prototypes if you have any good suggestion. Does that answer your question? Andreas --- In [email protected], "jacky11287" <[EMAIL PROTECTED]> wrote: > > Hi Andreas, > > I am Jacky, I am currently dealing with a web map SVG based > project, sounds similiar to the work of your project. I studies your > project, including this one and the example 5. > > I studied quite deeply in the example 5, but I encountered some > conceptual problem while studying the query part. May I raise a > question here? I just would like to make clear how does the work of > the function "intersection" and what exactly the semantic is about > the query? > > Since, as my understanding, the query is > > Select AsSVG(Intersection(Simplify(g, $), geomfromtext(the bbox of > the new view)..) From ... Where g && setSRID(new view box-the same as > the one in select sub clause) and level... > > The semantic is to select the new view box geometry, then simplify > it as the result intersec with its own view box. How can this query > finish the job just querying the missing part of map data when you pan > the map? That is, the old view box overlaps with the new view box, the > example query only the missing part, in my understanding, the query > seems not completely done the job...(or something I missed?) > > In my own understanding, I will do like, just query the missing two > rectangle when the two view box overlap in this case, but not that > easy as you done in example 5. Sorry for my miss understanding > somewhere, I do know that I must miss the important part, so that I > raise the question here, hope you don't mind....^.^ > > Looking forward to your reply!! > > Have a nice day~~ > > Jacky > ----- 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/
