[OSM-talk] LU overlay idea

[Artem Pavlenko]

On 5 Jun 2007, at 13:25, Knut Arne Bjørndal wrote:

> Artem Pavlenko <artem at mapnik.org> writes:
>> On 29 May 2007, at 00:08, Robert (Jamie) Munro wrote:
>>     Finally, can openlayers only offer the "tube" overlay if you are
>>     browsing somewhere near London and zoomed in a bit? It would  
>> be really
>>     silly if when browsing places with no mass transit for miles  
>> if the
>>     server has to serve lots of empty transparent tiles, and when  
>> you click
>>     the dropdown you get options that are never going to make any
>>     difference. This obviously becomes much more significant if we  
>> start
>>     adding more layers that are only interesting to other parts of  
>> the
>>     world. The other option, of course, is for all underground  
>> railway and
>>     tram systems globally to share a layer. But most of the world  
>> doesn't
>>     have either, and other layers we may develop in future may  
>> only be
>>     relevant outside cities etc.
>>
>> I'm not sure OL can do this. It looks like it should be done at JS  
>> level but
>> without reloading the whole page.
>> AJAX ? It is certainly an important feature for multi layered  
>> regional maps.
>
> It should certainly be possible to make some javascript that gets
> fired when the user pan or scroll and shows or hides a layer based on
> wheather the center point is inside a bounding box and zoom level.
>
> You would also want to add something that remembers whether the user
> last had the layer displayed, and made sure to set it to the same
> value.
>
> Does anybody who actually know javascript volunteer to do this, or
> will I have to try and cludge something together?

Well, I'm happy to help but I don't really know JS. I think a generic  
modules that would allow *dynamic* adding/removing Layers objects  
depending on position/zoom level would be useful. OL might have  
something like that already.

Cheers,

>
> -- 
> Knut Arne Bjørndal
> aka Bob Kåre
> bob at cakebox.net
> bobkare
>

Artem Pavlenko
http://mapnik.org



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/talk/attachments/20070605/0a220353/attachment.html>