# [postgis-users] Error during the coordinate transformation

Fernando Javier Luyo Zegarra fluyoz at hotmail.com
Fri Mar 27 10:35:22 PDT 2009

```Hello,

I'm developed a routine for transforming coordinates of points which are in PSAD56 Zone 18S (srid = 24878) to Wgs84 Zone 18s (srid = 32718)

The items are stored in the fields "geom" the table "MyTable" (srid = 24878).

To perform the operation using the following syntax:

select Transform (geom, 32718) from MyTable

Reviewing the results found that there is an error:

Example:

X = 264365.2955 Y = 8665287.3660 Z = 0.0000

The result of the transformation is:

X = 264366.1196 Y = 8665292.17 Z = 0.0000

However, the same point in cartografia WGS84 Zone 18S has the following coordinates:

X = 264143.0640 Y = 8664919.0231 Z = 0.0000

Apparently the SRID of the parameters are not properly used or applied incorrectly the function Transform ()

Fernando Luyo
pd: Sorry for my bad English

**************************************************

Hola

Estoy elaborando una rutina para transformar coordenadas de puntos que estan en PSAD56 Zona 18S (srid=24878) a Wgs84 Zona 18s (srid=32718)

Los puntos estan almacenados en el campo "geom" de la tabla "MyTable" (srid=24878).

Para realizar la operacion estoy usando la siguiente sintaxis:

select Transform(geom,32718) from MyTable

Al revisar los resultados encontre que hay un error :

Ejemplo :

X = 264365.2955     Y = 8665287.3660     Z = 0.0000

El resultado de la transformacion es:

X = 264366.1196     Y = 8665292.17       Z = 0.0000

Sin embargo, el mismo punto en cartografia en WGS84 Zona 18S tiene las siguientes coordenadas:

X = 264143.0640     Y = 8664919.0231     Z = 0.0000

Al parecer los parametros de los SRID usado no estan correctos o estoy aplicando mal la funcion Transform()

A la espera de su ayuda

saludos

Fernando Luyo

**************************************************

_________________________________________________________________
Explore the seven wonders of the world
http://search.msn.com/results.aspx?q=7+wonders+world&mkt=en-US&form=QBRE
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20090327/dbbac061/attachment.html>
```