[Mapserver-users] Oracle Spatial Extents

[Frans Knibbe]

Vladimir,

Ah, I understand now, you want the MBR of the entire table/layer, not of 
every single geometric object...
It is strange that  SDO_AGGR_MBR also takes too long, I would expect it 
to execute faster. Have you also tried SDO_TUNE.EXTENT_OF?

Are your data often modified? If the geometric data are not changing, 
you could also queryuser_sdo_geom_metadata,  because the extent of the 
entire layer is stored there.
Did you update user_sdo_geom_metadata after projecting the data?

You were right about your data not being geodetic.  The difference is 
that geodetic co-ordinates indicate a point on a sphere or sphere-like 
object, whereas projected co-ordinates generally indicate a point on a 
flat surface. The first co-ordinate system you used (SRID 8307) was 
geodetic, and that is why you weren't able to use the MBR functions. You 
can tell whether a co-ordinate system is geodetic by looking at the 
tabel MDSYS.CS_SRS. The column WKTEXT holds the Well Known Text 
description fort each SRID. If it starts with "GEOGCS", the co-ordinate 
system is geodetic.

Good luck,

Frans


> Hi, Frans.
>
> It takes 29 secs to get the full extents of the geometry, which has 
> ~2500 elements.
> The oracle gets all the ~2500 extents, and then gets the minimum and 
> maximum value for X and Y, so I obtain the full extents this way.
> I'm using Oracle Spatial 9i.
> My data is not geodetic (SRID=1=>Sinusoidal WGS84)
> I don't understand very well the difference between geodetic and 
> non-geodetic data, anyway, at the beginning I had my data in SRID=8307 
> and I wasn't able to use the MBR functions, so I switched to SRID=1.
>
> And trying the Fernando Simon's suggestion 
> (http://mapserver.gis.umn.edu/data2/wilma/mapserver-users/0407/msg00767.html), 
> I had no luck.
> The level with SDO_TUNE.ESTIMATE_TILING_LEVEL was 6, but the query 
> didn't get better.  Besides, after indexing this way I wasn't able to 
> draw the geometry outside the extents.
>
> My question now is: Is there another way to get the extents of a 
> geometry?
> I also tried SDO_AGGR_MBR with the same results (too much time 
> executing the query).
>
> The point is that I use a lot this functionality in Postgis 
> (extent(the_geom)) with very large datasets and Postgis does it very 
> fast.
>
> Any help will be very appreciated.
>
> Thanks a lot in advance,
>
>