[postgis-users] Can I replace all the x and y coordinates of a geometry using PostGIS, Thank you!

[ZHANGAIGUO]

Hi, Leo:

 

Thank you for your reply!

May be I did not tell my problem clearly,

Now, I want to know how i can get the number of points that stand for a polygon.

Just like the function of NumPoints(geometry) used for linestring.

 

And how can I locate each coordinate in the polygon?

Looking forward your reply!

Thanks a lot!

 

ZHANG Aiguo


 


From: lr at pcorp.us
To: postgis-users at postgis.refractions.net
Date: Wed, 11 Nov 2009 13:39:20 -0500
Subject: Re: [postgis-users] Can I replace all the x and y coordinates of a geometry using PostGIS, Thank you!




Not sure what you are trying to do, but one of the affine functions like ST_Translate may be what you are looking for.
 
http://www.postgis.org/documentation/manual-1.5SVN/ST_Translate.html
 
That will move all the points in the geometry a specified amount in x,y,z 
 
Leo
 



From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of ZHANGAIGUO
Sent: Wednesday, November 11, 2009 11:50 AM
To: postgis-users at postgis.refractions.net
Subject: [postgis-users] Can I replace all the x and y coordinates of a geometry using PostGIS, Thank you!


Hello Postgis-users:

I am a student in Fuzhou University, China.
In using PostGIS,
I encountered a problem as fellows:
How can I replace all the x and y coordinates of a geometry?
The geometry may be point, multipoint, linestring, multilinestring, and so on.
I have tried to use the way as fellows:

CREATE OR REPLACE FUNCTION aigo_coord_offset_basicframe2(geometry, double precision, double precision)
   RETURNS geometry AS
 $BODY$
 declare i integer; 
 compress geometry; 
geom1 geometry;
 begin
 i:=1;
 geom1:=ST_GeomFromText('LINESTRING(0 0, 0.0001 0.0001)',21460);
 while i<= ST_NumPoints($1) loop
 geom1:=ST_AddPoint(geom1,ST_MakePoint(int2(ST_X(ST_PointN($1,i))-$2),int2(ST_Y(ST_PointN($1,i))-$3)));
 i:=i+1;
 end loop;
 geom1:=ST_RemovePoint(geom1,0);
geom1:=ST_RemovePoint(geom1,0);
compress:=geom1;
return compress;
end $BODY$
   LANGUAGE 'plpgsql' VOLATILE
  COST 100;
 ALTER FUNCTION aigo_coord_offset_basicframe2(geometry, double precision, double precision) OWNER TO post;
 
 The way above is just applied to LINESTRING geometry type,
 and it is inefficient.
 
 Are there any other solutions to accomplish it?
 Thank you!

 Sincerely Yours!
 ZHANG Aiguo



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