Topic: Smart map overlays with georss

Hello!

I am designing a "map" view for the ads on my classifieds site. (see it as it progresses at http://safarri.com/map).
I started out using Google's map API, but just switched to Yahoo. (I am open to either, suggestions apreciated).

I understand the basic syntax for creating map overlays, but as far as I can see it provides no method for loading ONLY markers that are in view. What I want people to be able to do is enter the map mode, zoom in to their local area, and have the map dynamically load markers for the viewed area (it will also be able to filter the markers based on a whole bunch of criteria, I can handle that :-) ).

I noticed that the Yahoo API has a class for overlaying a georss feed on the map. I think what I want to do is set up my server to be able to create georss feeds of ads in a certain latlon "box", and then request a new feed to overlay whenever the user scrolls out of that box. Will I need to store all the "boxes" in an array? How will I tell when the user moves their viewed area? Thats what I need help with. I scoured the internet for tutorials, but was unable to find any.


P.S. Here is a flowchart to help you understand what I mean:

1) User enters "map" mode.
2) Map initializes, and requests georss feed from server for viewed area
3) User interacts with map, and finally moves it
4) map requests new georss feed from server for new area

Note: Requested georss feeds should not overlap. We need some way to intelligently tile them...


-Robur