[pgrouting-users] problems with pgr_pointsAsPolygon

[Daniel Kastl]

Hi Dave,

There was a blog post I wrote long time ago, but after some improvements to
the pgr_pointsAsPolygon function, when it supported a custom value for
"alpha":
https://georepublic.info/en/blog/2017/catchment-area-calculation-with-pgrouting/

I don't remember details anymore, just that I wrote that post and the
result was quite OK.
It seems I got more detailed boundaries, when the alpha value was pretty
small like "0.00001".
Have you tried such a small number?

Best regards,
Daniel



On Wed, Oct 10, 2018 at 1:43 AM Dave Potts <mrdapotts at gmail.com> wrote:

> I have a collection of x,y points and I am trying to draw a bounding
> polygon. I was unhappy with the default returned, so I decided to a play
> with the alpha parameter.
>
> I get no result and the value 'NOTICE:  n = 1'
>
> printed on the console,
> My sql is
>
> pgr_pointsAsPolygon('select id,st_x(st_startpoint(the_geom)) as x,
> st_y(st_startpoint(the_geom)) as y from tmp where label=27,5.0);
>  select pgr_version() returns psql (10.5 (Ubuntu 10.5-1.pgdg16.04+1))
> The machine is running postgres 10.5-1
>
> Is there anything wrong with what I am doing? Using an alpha value of 0
> does not generate an error.
>
> regards
>
>
> Dave.
>
>
>
>
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-- 
Georepublic UG & Georepublic Japan
eMail: daniel.kastl at georepublic.de
Web: https://georepublic.info
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