Re: Questions about ESRI shapefiles and projections

Hi Scottie,

On Wednesday, May 22, 2002, at 01:36 PM, Scott Bortman wrote:

> Hello fellow OpenMap users,
>
> I have some questions about ESRI shapefiles and Projections:
>
> Is there a default projection associated with a shapefile?

There isn't. The graphics in the shapefile can be defined in any
coordinate system.

OpenMap only properly handles Shape files that contain graphics defined
in decimal degrees. The code will read any shape file, it just doesn't
render any projected graphics properly.

> Or is the projection info buried withing the shapefile itself?

The Shape file specification doesn't know anything about projections.

> If it is in the file, how can I determine what projection was
> used to encode the data contained within a shapefile. Is there
> an OpenMap method that can extract it?

Cheers,

Don

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Don Dietrick, BBN Technologies, dietrick@bbn.com
10 Moulton Street, Cambridge, MA 02138
617-873-3031 [fax]-2794
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