[Proj] Error during the coordinate transformation?

[Clifford J Mugnier]

Fernando,
 
Check out my column on Perú in Photogrammetric Engineering and Remote Sensing from May of 2006.  I have more than one set of parameters listed between PSAD56 and WGS84.  (One is from the U.S. Military, and a different one is from the Instituto Geografico Militar in Perú.)
 
www.ASPRS.org/resources/grids
 
C. Mugnier
LSU

________________________________

From: proj-bounces at lists.maptools.org on behalf of Fernando Javier Luyo Zegarra
Sent: Wed 01-Apr-09 14:32
To: proj at lists.maptools.org
Subject: Re: [Proj] Error during the coordinate transformation?



Hi

The code corresponds to Perú
Fernando






________________________________

Date: Tue, 31 Mar 2009 16:17:29 -0500
From: cjmce at lsu.edu
To: proj at lists.maptools.org; proj at lists.maptools.org
Subject: Re: [Proj] Error during the coordinate transformation?


Dear Fernando:
 
What country is this, and what parameters did you use.  I suspect you're in Venezuela ... please confirm.
 
Estan usted en la Republica de Venezuela?  Esta verdad?
 
C. Mugnier
Louisiana State University

________________________________

From: proj-bounces at lists.maptools.org on behalf of Fernando Javier Luyo Zegarra
Sent: Tue 31-Mar-09 16:11
To: proj at lists.maptools.org
Subject: [Proj] Error during the coordinate transformation?



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:

Point in Psad56 Zn 18s

        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 ()

While waiting for your help


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 : 

Punto en Psad56 Zn 18s

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< br>
saludos

Fernando Luyo

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




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