[postgis-users] Re: "Summarizing" a collection of geometries

[Reid Priedhorsky]

Kevin Neufeld wrote:
> Hi Reid,
> 
> I'm not sure I fully understand your use case, but you may be able to
>  make use of PostgreSQL's schemas and duplicate your source data in 
> several schemas, where each schema represents a simplification of
> your dataset.

Hi Kevin,

Thanks for the note.

The use case is basically indicating to users where they might like to
zoom in if they want to see more details. So, the summary doesn't need
to accurately represent the summarized geometries, just show roughly 
where they are.

They will be seeing the summaries from scales of about 1 meter/128
pixels up to 1 meter/8 pixels. Above this scale we show the actual geometry.

The summaries will be fetched as vectors, not rasters.

Did this scheme seem reasonable?

> 1. Use ST_Buffer() to compute polygon buffers around members of the
> collection. Question: ST_Buffer() docs say it can't handle
> GeometryCollections. What about e.g. MultiPoint or MultiPolygon?
> 
> 2. Take the ST_Union() of the result of #1, producing a MultiPolygon.

Thanks,

Reid