[postgis-users] st_distance meter/degree

[Olivier Leprêtre]

De : postgis-users [mailto:postgis-users-bounces at lists.osgeo.org] De la part de franco base
Envoyé : jeudi 13 avril 2017 13:08
À : PostGIS Users Discussion
Objet : Re: [postgis-users] st_distance meter/degree

 

Sorry.

I don't see the 10-5at the end 

very sorry

 

2017-04-13 13:05 GMT+02:00 Jorge Gustavo Rocha <jgr at di.uminho.pt>:

Hi Franco,

I did not understood your question.

Postgis calculates the distance/area according to the CRS unit. It the
CRS unit is degrees, the results is in degrees. If the CRS unit is
meter, the result is in meter.

For example, if you transform the geometry, like:
SELECT ST_Distance(ST_Transform(geometry, 25829)) ...
the result will be in meter.

Regards,

Jorge

Às 11:54 de 13-04-2017, franco base escreveu:
> Thanks Jorge but it isn't the matter.
> I'd know why postgis have a different way to calculate the distance
> with the same sql query.
>
> 2017-04-13 12:37 GMT+02:00 Jorge Gustavo Rocha <jgr at di.uminho.pt
> <mailto:jgr at di.uminho.pt>>:
>
>     Hi Franco,
>
>     You can use the usual control statements IF THEN ELSE [1] to make it
>     exactly like you want.
>
>     [1]
>     https://www.postgresql.org/docs/current/static/plpgsql-control-structures.html
>     <https://www.postgresql.org/docs/current/static/plpgsql-control-structures.html>
>
>     Regards,
>
>     Jorge
>
>     Às 10:57 de 13-04-2017, franco base escreveu:
>     > Hi all.
>     > Is it possible that st_distance between point return meter distance if
>     > point are very close and degrees otherwise?
>     >
>     > SELECT ST_distance ( ST_SetSRID
>     > (ST_MakePoint(45.4553804010375,9.11292550791171) ,4326), ST_SetSRID
>     > (ST_MakePoint(45.4553855607023,9.11291318106981) ,4326))
>     >
>     > return 1.3 ( meter distance)
>     >
>     >
>     > SELECT ST_distance ( ST_SetSRID
>     > (ST_MakePoint(45.4553804010375,9.11292550791171) ,4326), ST_SetSRID
>     > (ST_MakePoint(45.4560699405679,9.1164832309759) ,4326))
>     >
>     > return 0.003 (degrees distance)
>     >
>     >
>     > Thanks
>     > fb
>     >
>     >
>     >
>     >
>     >
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>     >
>
>     J. Gustavo
>     --
>     Jorge Gustavo Rocha
>     Departamento de Informática
>     Universidade do Minho
>     4710-057 Braga
>     Tel: +351 253604480 <tel:%2B351%20253604480>  <tel:%2B351%20253604480>
>     Fax: +351 253604471 <tel:%2B351%20253604471>  <tel:%2B351%20253604471>
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>
>
>
>
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>

J. Gustavo
--
Jorge Gustavo Rocha
Departamento de Informática
Universidade do Minho
4710-057 Braga
Tel: +351 253604480 <tel:%2B351%20253604480> 
Fax: +351 253604471 <tel:%2B351%20253604471> 
Móvel: +351 910333888 <tel:%2B351%20910333888> 
skype: nabocudnosor
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