[postgis-users] Expand odd shapes

[Andy Colson]

Because I actually need to see the shape.  One step is to see the shape, 
the second will be to find the parcels that touch it, which will use 
ST_DWithin for speed plus ST_Buffer for accuracy.

-Andy


On 6/10/2015 1:43 AM, Rémi Cura wrote:
> Why not use ST_DWithin with the original triangle, it is the best option
> regarding speed and precision.
> Cheers
> Remi-C
>
> Le 10 juin 2015 01:30, "Andy Colson" <andy at squeakycode.net
> <mailto:andy at squeakycode.net>> a écrit :
>
>     At first I thought no, because it creates a circle around a point:
>
>     "Returns a geometry that represents all points whose distance from
>     this Geometry is less than or equal to distance"
>
>     But now that I read it again, maybe it does do what I'd like.  If I
>     pass a rectangle, it'll return all points <= radius.
>
>     I'll give it a shot and try it out.  Thanks for the help.
>
>     -Andy
>
>
>     On 06/09/2015 04:48 PM, Basques, Bob (CI-StPaul) wrote:
>
>         Can you use ST_Buffer??
>
>         bobb
>
>
>
>             On Jun 9, 2015, at 4:34 PM, Andy Colson
>             <andy at squeakycode.net <mailto:andy at squeakycode.net>> wrote:
>
>             Hi all.
>
>             I have buffer selection problem.  My site can drop a point,
>             then find all the parcels within 100 feet of that point.  No
>             problem.
>
>             One client however would like to select a parcel (maybe its
>             a square, maybe its a triangle, or any other odd shape), and
>             find all other parcels within 100 feet of any point within
>             the source parcel.
>
>             100 is optional.  They could choose 50, or 150.
>
>             I'm not sure how to do something like this.  I found
>             ST_Expand, but that'll create a bounding box around the
>             triangle.
>
>             ST_TransScale could scale it, but I'm not sure what the
>             scale is.  The user might type in 50 feet or 150 feet, I'm
>             not sure how to calculate a deltaX and deltaY scale for that.
>
>             Any hints on how I might go about this?  I'm a bit stuck.
>
>             Thanks,
>
>             -Andy
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