# SDO_CS.TRANSFORM gives unexpected results

**983826**Jan 28, 2013 12:58 AM

Gurus,

would anyone help me to discover how the coordinate system operations work in Oracle 11g?

I am trying to transfrom from local Czech coordinate system (SRID 2065) to ETRS-89 (SRID 4258):

In Ora 11g I get:

Changing the parameters for datum transformation (mdsys.sdo_datums) does not seem to influence the results. Hence I am not sure if this is the correct place to change the x-y-z shifts/rotations and scale_adjust.

In Ora 11g I get:

I have checked that the Oracle defaults for the 7-param.transformation are very close to what we are using in Intergraph Geomedia, which give us acceptable results, which are again very close to the results given by Transformation service of Geoportal of Czech National Mapping Agency.

I would appreciate any comments...

Thank you.. Vlad

would anyone help me to discover how the coordinate system operations work in Oracle 11g?

I am trying to transfrom from local Czech coordinate system (SRID 2065) to ETRS-89 (SRID 4258):

**-- TEST sdo_cs.transform FORWARD****select sdo_util.to_wktgeometry(sdo_cs.transform(sdo_geometry(2001,4258,sdo_point_type 14,50,null),null,null),2065)) as wkt_geom from dual;**In Ora 11g I get:

POINT (774135.822823993 1048589.68103062)However, correct result should be

POINT (774041.368 1048448.779)Source: Transformation service of Geoportal of Czech national mapping agency http://geoportal.cuzk.cz/Default.aspx?head_tab=sekce-01-gp&mode=TextMeta&text=wcts&menu=19

Changing the parameters for datum transformation (mdsys.sdo_datums) does not seem to influence the results. Hence I am not sure if this is the correct place to change the x-y-z shifts/rotations and scale_adjust.

**-- TEST sdo_cs.transform REVERSE****select sdo_util.to_wktgeometry(sdo_cs.transform(sdo_geometry(2001,2065,sdo_point_type(774135.822823993,1048589.68103062,null),null,null),4258)) as wkt_geom from dual;**In Ora 11g I get:

POINT (14.0 50.0000000647905)According my experience the coordinate conversion is normally done in two steps (reverse case):

1. projected coordinates in SRID 2065 are converted (by reverse Krovak projection algorithm, coord_op_id=9819) to geographic coordinates in S-JTSK/GEOGRAPHIC2D (SRID 4156), datum "Jednotne Trigonometricke Site Katastralni" (EPSG ID 6156) based on Bessel Ellipsoid (EPSG ID 7004)

2. then the geographic coordinates should be transformed using Position Vector 7-param. transformation (coord_op_id=9606) to ETRS-89 (SRID 4258)Assuming that above two steps are true in Oracle, and the projection algorithm (coord_op_id=9819) is correctly implemented (I wonder if it is, btw is it hardcoded?), then we should get the expected results.

I have checked that the Oracle defaults for the 7-param.transformation are very close to what we are using in Intergraph Geomedia, which give us acceptable results, which are again very close to the results given by Transformation service of Geoportal of Czech National Mapping Agency.

I would appreciate any comments...

Thank you.. Vlad

- 200 Views
- Tags: none (add)