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All Blog Articles, Data Models and Free Source Code by Simon Greener, The SpatialDB Advisor is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

Implementing a Rotate/ST_Rotate function for Oracle Spatial

Friday January 16 2009 at 22:30

One very useful function that is missing in Oracle Spatial/Locator is the ability to rotate an sdo_geometry object.

A few years ago I wrote a function in my free PL/SQL packages but recent work with PostGIS occasioned my going back to that function and updating it.

The function, and its overloads, are:

create or replace package Geom
AUTHID CURRENT_USER
Is
...

  Function Rotate (
    p_geometry in MDSYS.SDO_Geometry,
    p_dimarray in MDSYS.SDO_Dim_Array,
    p_X        in number,
    p_Y        in number,
    p_rotation in number := 0)
    return MDSYS.SDO_Geometry deterministic;

  /**
  * Overloads of main Rotate function
  **/
  Function Rotate( p_geometry  IN MDSYS.SDO_GEOMETRY,
                   p_tolerance IN number,
                   p_rotation  IN number := 0)  -- 0 to 360 degrees
    Return MDSYS.SDO_GEOMETRY Deterministic;

  Function Rotate( p_geometry  IN MDSYS.SDO_GEOMETRY,
                   p_tolerance IN number,
                   p_X         IN number,
                   p_Y         IN number,
                   p_rotation  IN number := 0)  -- 0 to 360 degrees
    Return MDSYS.SDO_GEOMETRY Deterministic;

  Function Rotate( p_geometry IN MDSYS.SDO_GEOMETRY,
                   p_dimarray IN MDSYS.SDO_DIM_ARRAY,
                   p_rotatePt IN MDSYS.SDO_Point_Type,
                   p_rotation IN number := 0)  -- 0 to 360 degrees
    Return MDSYS.SDO_Geometry Deterministic;

Let’s explore rotation.

Firstly, let’s define a rectangular polygon whose WKT is:

“POLYGON ((2 2, 2 7, 12 7, 12 2, 2 2))”

Original Rectangle Polygon before Rotation

Then, let’s rotate it about itself, 45 degrees. In the following call, the false orig rotation parameters (p_x and p_y) are set to NULL. The Rotate function then gets the Minumum Bounding Rectangle (MBR) of the rectangle, extracts its centre, and then rotates about that point.

select Geom.Rotate(mdsys.sdo_geometry('POLYGON((2 2, 2 7, 12 7, 12 2, 2 2))',NULL),0.05,45) 
  from dual; 

GEOM45
-------------------------------------------------------------------------------------------------------------------------------------------
MDSYS.SDO_GEOMETRY(2003,null,null,MDSYS.SDO_ELEM_INFO_ARRAY(1,1003,1),MDSYS.SDO_ORDINATE_ARRAY(5.2,-0.8,1.7,2.7,8.8,9.8,12.3,6.3,5.2,-0.8))

1 rows selected

And this looks like:

Original Rectangle after Rotation 45 degrees

(Now, it appears that the Rotate function in PostGIS only rotates around the origin of the co-ordinate system. Thus to achieve the above one must translate the geometry to the origin, rotate it, then translate it back. Here is a blog on how to do this in PostGIS. Even though my Rotate function has all this built in, this is how one would do what my PostGIS friends did:

SELECT geom.st_translate(
       geom.rotate(
       geom.st_translate(the_geom,-x,-y),
       0.005,null,null,45),
       x,y) as GEOM45
  FROM ( SELECT the_geom, 
                geom.sdo_centroid(the_geom,0.005).sdo_point.x as x,
                geom.sdo_centroid(the_geom,0.005).sdo_point.y as y
           FROM (SELECT mdsys.sdo_geometry('POLYGON((2 2, 2 7, 12 7, 12 2, 2 2))',null) as the_geom 
                   FROM dual )
        );

GEOM45
--------------------------------------------------------------------------------------------------------------------------------------
MDSYS.SDO_GEOMETRY(2003,null,null,MDSYS.SDO_ELEM_INFO_ARRAY(1,1003,1),MDSYS.SDO_ORDINATE_ARRAY(5.23,-0.8,1.7,2.73,8.77,9.8,12.3,6.27,5.23,-0.8))

1 rows selected

I think having it all inside the Rotate function is neater but less “orthogonal”.)

Now, let’s rotate about the 0,0 axis.

select Geom.Rotate(b.the_geom,0.05,0,0,45 ) as geom00
  from (select mdsys.sdo_geometry('POLYGON((2 2, 2 7, 12 7, 12 2, 2 2))',NULL) as the_geom
         from dual
       ) b;

GEOM00
--------------------------------------------------------------------------------------------------------------------------------------
MDSYS.SDO_GEOMETRY(2003,null,null,MDSYS.SDO_ELEM_INFO_ARRAY(1,1003,1),MDSYS.SDO_ORDINATE_ARRAY(0,2.8,-3.5,6.4,3.5,13.4,7.1,9.9,0,2.8))

1 rows selected

Which looks like:

Original rectangle rotated 45 degrees around origin 0,0

We can do some cool things.

First, let’s take a single point (0,10) and rotate it around 359 degrees.

select a.column_value as oid,
       CONCAT('degrees = ',to_char(a.column_value,'999')) as descptn,
       geom.rotate(mdsys.sdo_geometry(2001,null,sdo_point_type(0,10,Null),null,null),0.0005,0,0,a.column_value) as geom
  from table(geom.generate_series(1,359,1)) a;

oid descptn geom
1 degrees = 1 MDSYS.SDO_GEOMETRY(2001,null,MDSYS.SDO_POINT_TYPE(-0.175,9.998,null),null,null)
2 degrees = 2 MDSYS.SDO_GEOMETRY(2001,null,MDSYS.SDO_POINT_TYPE(-0.349,9.994,null),null,null)
… … …
359 degrees = 359 MDSYS.SDO_GEOMETRY(2001,null,MDSYS.SDO_POINT_TYPE(0.175,9.998,null),null,null)

Visually…

Point 0,10 rotated 359 times

Finally, let’s take a single slice of a 2 degree pie and rotate it fully around the circle.

Single 2 degree sector of a pie

select a.column_value as oid,
       CONCAT('Sector = ',to_char(a.column_value,'999')) as descptn,
       geom.rotate(MDSYS.SDO_GEOMETRY(2003,null,null,MDSYS.SDO_ELEM_INFO_ARRAY(1,1005,2,1,2,2,5,2,1),MDSYS.SDO_ORDINATE_ARRAY(-0.175,9.998,-0.349,9.994,-0.523,9.986,0,0,-0.175,9.998)),0.0005,0,0,a.column_value) as geom
  from table(geom.generate_series(1,360,2)) a;

oid descptn geom
1 Sector = 1 MDSYS.SDO_GEOMETRY(2003,null,null,MDSYS.SDO_ELEM_INFO_ARRAY(1,1005,2,1,2,2,5,2,1),MDSYS.SDO_ORDINATE_ARRAY(-0.349,9.993,-0.523,9.986,-0.697,9.975,0,0,-0.349,9.993))
3 Sector = 3 MDSYS.SDO_GEOMETRY(2003,null,null,MDSYS.SDO_ELEM_INFO_ARRAY(1,1005,2,1,2,2,5,2,1),MDSYS.SDO_ORDINATE_ARRAY(-0.698,9.975,-0.872,9.962,-1.045,9.945,0,0,-0.698,9.975))
… … …
359 Sector = 359 MDSYS.SDO_GEOMETRY(2003,null,null,MDSYS.SDO_ELEM_INFO_ARRAY(1,1005,2,1,2,2,5,2,1),MDSYS.SDO_ORDINATE_ARRAY(0,10,-0.175,9.999,-0.349,9.994,0,0,0,10))

Visually…

Single piece of pie rotated around circle

I hope this is of interest.

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Comment [4]

Hi Simon,

I’m trying to rotate a point but I’m getting an error:

Here : spatial.centroid.sdo_centroid(geometry,0.005).sdo_point.x or spatial.centroid.sdo_centroid(geometry,0.005).sdo_point.y

ORA-20001: ORA-20001: ORA-06531: Reference to uninitialized collection
ORA-06512: at “MDSYS.SDO_UTIL”, line 371
ORA-06512: at “SPATIAL.CENTROID”, line 961
ORA-06531: Reference to uninitialized collection
ORA-06512: at “SPATIAL.CENTROID”, line 1253
ORA-20001: ORA-06531: Reference to uninitialized collection

Please, could you help me ?

Thanks in advance ,

Ricard.

Great packages! Good job.

— Ricard Fusté · 25 March 2010, 22:01 · #

Ricard,

If you are trying to rotate a point why are you using sdo_centroid?

Also, a centroid from a single point is itself so there is no need to call sdo_centroid on a point. (On a multi-point, yes, but not a point).

So, if you are calling sdo_centroid with something like:

sdo_geometry(2001,NULL,SDO_POINT_TYPE(1,2,NULL),NULL,NULL)

The sdo_centroid will fail at line 961. I will modify the code to fix this situation.

But, firstly, are you calling sdo_centroid with a sdo_point_type sdo_geometry?

regards
Simon

— Simon · 26 March 2010, 10:54 · #

I’m interested in the free PL/SQL package for rotate geometries (affine) transformations in ORACLE 10 as you mentioned in this article. Is it available ?
Thanks
Jasper Miller

— Jasper Miller · 3 September 2010, 17:10 · #

Yes, Jasper, download the free PL/SQL packages and install. The functions you are after are in the GEOM package:

GEOM.ROTATE (various call signatures)
GEOM.AFFINE
GEOM.MOVE/ST_TRANSLATE
GEOM.SCALE

Please let me know how you go with the install and use.

regards
Simon

— Simon Greener · 4 September 2010, 11:44 · #