[postgis-users] Solar azimuth calculator

[Alexander Gataric]

Does anyone have the SQL for PostGIS to calculate the solar azimuth and elevation for a time and point?

Thanks 

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On Apr 12, 2021, 8:38 AM, at 8:38 AM, "Palacios García Cuevas, Elena" <epgcuevas at indra.es> wrote:
>Thank you Martin.  With ST_ReducePrecision I got the expected result.
>The polygon, although is a complex one, is valid. I will file a ticket
>with a sample for the ST_Union issue.
>________________________________
>De: postgis-users <postgis-users-bounces at lists.osgeo.org> en nombre de
>Martin Davis <mtnclimb at gmail.com>
>Enviado: martes, 6 de abril de 2021 20:46
>Para: PostGIS Users Discussion <postgis-users at lists.osgeo.org>
>Asunto: Re: [postgis-users] Reduce precision using ST_union with
>gridSize
>
>The issue with ST_Union not working with an empty polygon certainly
>sounds like a bug, and we should look into that. If you can file a
>ticket that would be great.   (It would be helpful to have the polygon
>data which is causing the problem.  Is it valid?)
>
>In any case now there is the function ST_ReducePrecision [1] which is
>specifically designed to do what you want.  (It uses most of the same
>machinery as ST_Union, but should avoid whatever the issue with
>ST_Union is).
>
>[1] https://postgis.net/docs/manual-3.1/ST_ReducePrecision.html
>
>On Tue, Apr 6, 2021 at 7:28 AM Palacios García Cuevas, Elena
><epgcuevas at indra.es<mailto:epgcuevas at indra.es>> wrote:
>Hello,
>
>I am trying to simplify a polygon by reducing the precision using
>ST_Union with the gridSize parameter ( I am using  postgis 3.1  and
>GEOS 3.9.1). I have read that it is possible to do that by a union of a
>geometry with an empty geometry
>(http://blog.cleverelephant.ca/2020/12/waiting-postgis-31-3.html).  
>However, does not works for me ( maybe is my fault because I am new
>with postgis). I have tried as follows:
>
>CREATE TABLE public.error_union_empty
>(
>    geom geometry(MultiPolygon),
>    gid integer NOT NULL DEFAULT nextval('fallo_gid_seq'::regclass),
>    CONSTRAINT error_union_empty_pkey PRIMARY KEY (gid)
>);
>INSERT INTO error_union_empty
>(SELECT ST_union(geom,ST_GeomFromText('POLYGON EMPTY'), 0.001152) geom
>FROM f_polygon);
>
>But the result is an empty table.
>Then I tried to do the same but by doing the union with the polygon
>himself, and this approach seems to work ok.
>
>CREATE TABLE public.error_union_empty2
>(
>    geom geometry(MultiPolygon),
>    gid integer NOT NULL DEFAULT nextval('fallo_gid_seq'::regclass),
>    CONSTRAINT error_union_empty2_pkey PRIMARY KEY (gid)
>);
>insert into error_union_empty2
>select  ST_CollectionExtract(ST_union(f_polygon.geom,f_polygon.geom,
>0.001152)) geom
>from f_polygon;
>
>Why is not working the first approach? Have I missed something in the
>query?
>Any help or comments are welcome.
>Does anyone knows if  is expected to have a simplify with gridsize in
>the future?
>
>Thanks!
>
>
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