[gdal-dev] Merge all features in polygon shapefile with gdal

[Roger André]

Hey Steven,

Are you trying to do this via a spatially enabled database?  In PostGIS,
the dissolve syntax looks like this:

"SELECT dissolve_field, ST_UNION(geometry) FROM table GROUP BY
dissolve_field;"

Roger


On Mon, Jul 6, 2015 at 4:13 PM, Steven Lutz <steven at ruggedrocksoffroad.com>
wrote:

>  I've found some examples of how to dissolve features in a polygon using
> gdal but I'm not familiar with how to implement them.
> here is an example of what I've found, but I'm having trouble modifying it
>
> this is what I've come up with:
>
> ogr2ogr output.shp
>   input.
> shp -dialect sqlite -sql
> "SELECT ST_Union(geometry), dissolve_field FROM input GROUP BY dissolve_field"
>
>
> it looks to me that it is trying to do this operation based on specific
> attribute entries but I'm looking to ignore the attribute entrie and make
> all features into one.
> This is what I've tried:
> the 32768.shp has an attribute named BLOCK and it's still not working..
> any ideas? >ogr2ogr -f "ESRI Shapefile" output.shp 32768.shp -dialect
> sqlite -sql "select ST_union(block) from '32768'" Warning 6:
> Normalized/laundered field name: 'ST_union(block)' to 'ST_union(b
>
> I am confused as to what I should be putting in the parenthasis of
> ST_Union()
>
> Please advise.
> Thank you
>
>
> --
>  Steven Lutz
> President
> Rugged Rocks, LLC
> Sales & Support: (909)547-4651
> Nissan 4x4 Parts <http://ruggedrocks.com> / Off Road GPS Units & Maps
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