Database Software

I'm trying to simplify a layer with line (spaghetti) geometries that are geodetic (SRID 8307).

1. Does the SDO_SAM.SIMPLIFY_LAYER work with Geodetic data?

When I try to use sdo_sam.simplify_layer function, the number of vertices does not change, regardless of the "pct_area_change_limit" I use (the only parameter where I can change the value). I even tried 100 (which I take to mean 100%).

execute sdo_sam.simplify_layer('TRACK_TEST','SHAPE','SMPL_SHAPE', '10', '100');

Maybe this is only applicable for polygon data?

2. Should I use SDO_UTIL.SIMPLIFY, instead, for geodetic data?

I was able to create a simplified layer using SDO_UTIL.SIMPLIFY, but I had understood that the SDO_SAM.SIMPLIFY_LAYER was simply a wrapper around SDO_UTIL.SIMPLIFY. I incrementally tried increasingly larger values for the parameters in SDO_UTIL.SIMPLIFY, and it ended up that I had to change the threshold parameter to 10000, and the tolerance parameter to 9999 before I saw a significant difference in the number of vertices.

CREATE TABLE TRACK_TEST_2
AS SELECT ID,
sdo_util.simplify(
MDSYS.SDO_GEOMETRY(
A.SHAPE.SDO_GTYPE,A.SHAPE.SDO_SRID,A.SHAPE.SDO_POINT,A.SHAPE.SDO_ELEM_INFO,A.SHAPE.SDO_ORDINATES),
10000,9999) SMPL_SHAPE
FROM TRACK_TEST A;

3. Why are the parameters controlling the functions different for SDO_SAM.SIMPLIFY_LAYER (commit interval, pct_area_change_limit)
SDO_SAM.SIMPLIFY_GEOMETRY (tolerance,pct_area_change_limit)
and SDO_UTIL.SIMPLIFY (threshold, tolerance)?

I tried changing the tolerance in my layer's metadata, but that didn't seem to affect sdo_sam.simplify_layer.

4. Perhaps my data are not suited for simplifying, but I was hoping to achieve data that displayed more quickly in an on-line map viewer. Are the SIMPLIFY functions best suited to geometries with very closely spaced vertices?

Any insight would be appreciated!

--Nancy