Re: spatial index file

Hi Martijn,

The Spatial Index file helps with geographical filtering. It's very
similar to the .shx file in that it contains file offsets to each shape
in the .shp file, but it also contains bounding box information for
each shape as well. The com.bbn.openmap.layer.shape package uses it to
determine which shape graphics should be used from the .shp for a given
projection. The regular ShapeLayer re-reads the .shp file and
recreates appropriate OMGraphics for each projection (The
BufferedShapeLayer and EsriPlugIn read the file once and buffer
everything). Although it's a high I/O layer, it's better for memory
usage.

You used to have to create it before using the ShapeLayer, but it has
since been modified to create one if doesn't exist (and if it can). If
you are using the ShapeLayer in an applet for example, you'd have to
create one.

Hope this helps,

Don

On Friday, September 20, 2002, at 01:28 AM, MARTIJN VAN DER PAUW wrote:

> Hello,
>
> What actually does a spatial index file. I mean, I use shape files
> right now but haven't generated ssx files (yet) But everything
> seems to run as it should.So, does it add extra things or does it
> speed up the application?
>
> Martijn
>
>
>
>
> Martijn van der Pauw, internetontwikkelaar.
> Meteo Consult
> martijn@weer.nl
> tel: 0317 - 399800
> fax: 0317 - 423164
> http://www.weer.nl
>
> --
> [To unsubscribe to this list send an email to "majdart@bbn.com"
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>
>

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Don Dietrick, dietrick@bbn.com
BBN Technologies, Cambridge, MA
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

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