Splitting dataset into regions using sdo_relate

Question

Hi all,
I am having difficulty subdividing my dataset into different regions. I have the spatial data of the city auckland and found the co-ordinates of the lower left and upper right limits of the data. What I want to do now is to break up this dataset into 9 individual regions and assign an ID for each region. I have been trying to use to following query with not much luck...
select a.link_id from nz_testlinks_auck a where mdsys.sdo_relate(a.GEOM,
mdsys.SDO_GEOMETRY (2003,null,null,mdsys.SDO_ELEM_INFO_ARRAY(1,1003,3),
mdsys.SDO_ORDINATE_ARRAY(174.7083,-37.0141,174.7910,-36.9544)), 'mask=ANYINTERACT querytype=WINDOW')='TRUE';
When i put the outputted data into a table and view the data i notice that the rectangle has selected a lot more data than what was actually defined in the query. I have been using the network data model editor and MapBuilder to check the data and the co-ordinates.
And when i try to create another rectangle for another region next to the previous one like this...
select a.link_id from nz_testlinks_auck a where mdsys.sdo_relate(a.GEOM,
mdsys.SDO_GEOMETRY (2003,null,null,mdsys.SDO_ELEM_INFO_ARRAY(1,1003,3),
mdsys.SDO_ORDINATE_ARRAY(174.7910,-37.0141,174.8736,-36.9544)), 'mask=ANYINTERACT querytype=WINDOW')='TRUE';
it again selects a larger rectangle selecting about half the data from the previous rectangle selection as well.
Please assist me to solve this problem.
Look forward to your replies.
Avinash

Answer 1

Avinash,
Do you have geometries that cross your rectangle boundary, like a long line, or a large polygon? Which rectangle would you expect such a line or polygon to appear in?
Or are you saying that geometries that are completely disjoint from your rectangle are getting selected? If you think that's the case, try the sdo_geom.relate function with the 'determine' mask to verify the relationship between your rectangle and one of the unexpected geometries.
http://download.oracle.com/docs/html/B14255_01/sdo_objgeom.htm#BGHCDIDG
If you want to be sure that nothing gets selected twice by your rectangles the ANYINTERACT mask probably isn't a good choice. A mask of mask=INSIDE+COVEREDBY will be better, but you'll still have to decide what to do with stuff that crosses.
Matt