How to do mosaic for different two georaster object?

Question

I have done mosaic for single georaster object, But I can't do it for different two georaster object. Oracle returned the error: ORA-13419.
My PL/SQL code is:
DECLARE
gr sdo_georaster;
BEGIN
INSERT INTO georaster_table (georid, georaster) VALUES (1, sdo_geor.init('rdt_1')) RETURNING georaster INTO gr;
sdo_geor.mosaic('city_images', 'image', gr, null);
UPDATE georaster_table SET georaster=gr WHERE georid=1;
END;
There are two rows in city_images.I want to know how to set these data?

Answer 1

Will,
in general, all the images should be georeferenced. otherwise it would not make too much sense to do mosaic. so, you might want to load real image data from either georeferenced GeoTIFF files or TIFF plus TFW files.
but GeoRaster doesn't require the images must be georeferenced. In GeoRaster, any image can have a different ULT coordinate, which doesn't have to be (0,0). This is a special feature of GeoRaster, in considering most formats always treat the upper-left corner pixel of an image as the origin (0,0) only. So in the cell space, non-georeferenced images can be co-located in different areas and so they can be mosaicked as well. specifically, you loaded two GIF files. their current ULT coordinates in georaster must be (0,0). If you setup the UTL coordinates of them differently and properly, then you shall be able to do the mosaicking. the functions you can use are getULTCoordinate and setULTCoordinate.
hope this helps
Jeffrey