[OpenLayers-Users] selecting a feature in a base layer

[Alexandre Dube]

Hi,

You can only interact with vector features, not just plain images. The 
layer you're referring to ( country boundaries ) is a WMS layer so it 
returns an image only.

If the server that renders that image is also configured to return 
geometry ( like a WFS server for example ) then you could have a vector 
layer of country boundaries and interact with it. One major problem with 
this that the polygon features returned would contain a lot of geometry 
and take a lot of time to display. Browsing your map would be slow too. 
A common practice is to have a WMS layer on top zoom levels and have 
your vector features displayed on lower levels.

See the following example showing what I mean (zoom in/out the map) : 
http://dev4.mapgears.com/bdga/bdgaWFS-T.html

If you have your own data to play with, I would suggest you to read the 
following articles to create your own WFS server and play with your own 
data : http://mapserver.org/ogc/wfs_server.html

Best of luck with your learning and welcome to the community,

Alexandre

new2ms4w wrote:
> Hi,
>
> I used MapServer with OpenLayers to display the road map of a country. Now,
> I want to select a particular and add a moving object to it.
>
> Adding a moving object to the map is easy. ( I drew a point on the map and
> I'm just moving it by calling OpenLayers.Geometry.move() )
> However I want these points to move only on roads.
>
> So, first I need to select a road and then add the moving object. This is
> the hard part for me.
>
> The examples section has an example (OpenLayers Select Feature Example
> http://www.openlayers.org/dev/examples/select-feature.html )  showing how to
> select a point, line or polygon (or any vector feature) which I draw there
> by either drawing a box or moving mouse over the feature etc.
>
> But how do we select a feature from the base layer? (Does the base layer
> even have features at all?)
> By this what I mean is how do we select the country boundaries in the above
> webpage. 
>
> Thank you for your time. I'm a student just started using OpenLayers around
> 1 week back. So, please bear with my questions.
>
> ~PN
>   


-- 
Alexandre Dubé
Mapgears
www.mapgears.com