I've not tried to do exactly what you're describing, but I imagine it
would go something like this:
* The car is a Feature.Vector with an icon, and the Layer.Vector has a
ModifyFeature control attached to it to allow the point features to be
edited (the cars to be dragged).
* The layer has a featuremodified event handler, which sends an update
to the server in usual AJAX fashion. As such, the server can update its
own database of the features -- which you surely wanted to do anyway,
especially to set up the map initially, right?
So, that was the "send my updates to the server" component.
For the "update my map from the server periodically" component:
* Also, in the page has a function which is called via setInterval() It
fetches features from the server, say in GeoJSON format, and updates
them on the map. The handler would iterate over layer.features, check
ID#s or "last modified" timestamps or some such, and delete-and-replace
the features as appropriate.
* The simplest way to update the map would be layer.refresh() but that
may not be wholly suitable: the layer would flicker a bit as it
refreshed, and any feature you were in the middle of editing could be
refreshed and your changes lost. But it may be useful during an interim
proof-of-concept phase.
* For later development, you could reduce the volume of GeoJSON data by
filtering by a "last modified time" When a client sends an update, the
feature's timestamp is updated in the server's database; when a client
requests an update it sends a note of the last time it requested an
update so only very-recent changes are downloaded.
Anyway, those are some off the cuff thoughts. Will that help get you
started?
--
Greg Allensworth, Web GIS Developer
BS A+ Network+ Security+ Linux+ Server+
GreenInfo Network - Information and Mapping in the Public Interest
564 Market Street, Suite 510 San Francisco CA 94104
PH: 415-979-0343 x302 FX: 415-979-0371 email: [email protected]
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