Hi Michael,
I forget to say that the user could configure how things are symbolized.
That's annoying because I can't make any assumption on the symbology used.
There can be several different feature types on the map with different types of
geometry (point, polygon, ...) and different symbologies.
Moreover, for a given feature type, each feature can be represented differently
depending on the rules defined by the user (spatial condition, attribute
condition
or viewing scale condition). So each feature would require a different
threshold.
For example, the user can decide to represent a building by its bounds at given
scale and by a symbol at a smaller scale. When the user clicks out of the symbol
to select, for instance, the city where the building is located, if the
selection is based
on feature geometry and the selection area covers the building area then the
building
would be chosen instead of the city.
Apparently, for my case, there is no effective and accurate way to select a
Feature
by an approach based on the actual representation of the feature and not its
original
geometry.
I'm developping a web application so I'm considering using Geotools to make
the WFS-T transactions and turning to OpenLayers for rendering. It will give
the possibility to select a feature with great accuracy, even if it has moved.
Thank a lot for your help,
Yako Bak.
> Date: Thu, 14 May 2009 10:53:59 +1000
> Subject: Re: [Geotools-gt2-users] Selecting a feature represented by a symbol
> From: [email protected]
> To: [email protected]; [email protected]
>
> Hi Yako,
>
> > Because those point features are represented by big symbols and I want the
> > user to be able to select the feature by clicking anywhere on the symbol and
> > not having to find the center.
>
> Knowing the size of the symbol (I think you discussed this with Jody
> earlier ?) you could use that to set the threshold distance that I
> referred to. It's just another suggestion for how you might approach
> this problem but of course only you can judge what is best, both for
> you as the developer and for the user.
>
> > The other problem is that, features (i.e. like cars) can move during two
> > rendering.
>
> Ah, that's interesting. I didn't realize the renderings were
> snapshots of a dynamic system (sorry, I haven't read all of the
> previous discussion). I guess the first thing I'd try is to record the
> positions of the features at each rendering in some simple data
> structure. So each feature has lastPos and curPos and it is lastPos
> that you query with respect to the mouse click.
>
> Are you using a spatial index ?
>
> Michael
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