6.2 Image Reprojection
Image reprojection is the process of transforming an image from one SRS (spatial reference system, or coordinate system) to another.
Reprojection is particularly useful with certain GeoRaster operations that combine two or more objects, because it requires that all the GeoRaster objects involved be in the same SRS.
Basic reprojection in GeoRaster is performed by the SDO_GEOR.reproject procedure and requires that the source GeoRaster SRID be different from the output SRID.
Example 6-3 Image Reprojection
Example 6-3 reprojects a raster image that had been loaded into a GeoRaster object with SRID 4326, but needs to be reprojected to have the same SRID as other images previously stored with SRID 23619.
DECLARE
gr1 sdo_georaster;
gr2 sdo_georaster;
BEGIN
select raster into gr1 from georaster_load_table where georid = 10;
delete from georaster_table where georid = 54;
insert into georaster_table
values(54,'reprojected', sdo_geor.init())
returning georaster into gr2;
sdo_geor.reproject(inGeoRaster => gr1,
pyramidLevel => 0,
cropArea => null,
layerNumbers => null,
resampleParam => 'resampling=BILINEAR',
storageParam => null,
outSRID => 32619,
outGeoraster => gr2);
update georaster_table set georaster = gr2 where georid = 54;
commit;
END;
The same operation can be accomplished by the SDO_GEOR.rectify procedure, producing similar results. The SDO_GEOR.rectify procedure offers more capabilities and flexibility than SDO_GEOR.reproject; for example, the input and output SRID can be the same and users can specify the precise resolution of the output (see Image Rectification).
If a GeoRaster object does not have an associated SRS, the process for georeferencing and rectifying it is explained in Georeferencing GeoRaster Objects and Image Rectification.
Parallel reprojection is supported with the SDO_GEOR_AGGR.mosaicSubset procedure.
Parent topic: Image Processing and Virtual Mosaic