[postgis-users] Expand odd shapes

[Andy Colson]

Like this:

http://testmaps.camavision.com/map/cassmo?pin=080834303000032000

The blue part is the selected parcel.  The gray is the ST_Buffer.

-Andy


On 6/10/2015 8:27 AM, Andy Colson wrote:
> 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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