4.6 Querying and Updating GeoRaster Cell Data

To query cell (pixel) data of a GeoRaster object for processing and visualization, you can query the raster data for a cell (pixel), a range of cells, or the entire raster of a GeoRaster object:

• SDO_GEOR.getCellValue returns cell values of one or multiple layers or bands for a specified location.

• SDO_GEOR.getCellValues returns the cell values of one or more cells in an array.

• SDO_GEOR.evaluateDouble evaluates a direct location based on neighboring cell values by using a specified interpolation method, and returns the raster values (double precision numbers) for the specified bands or layers for that location. (See Interpolating Cell Values for more information.)

• SDO_GEOR.evaluateDoubles evaluates multiple locations using a specified interpolation method, and returns the raster values (double precision numbers) for the specified band or layer for those locations.

• SDO_GEOR.getRasterSubset creates a single BLOB object or a single in-memory SDO_NUMBER_ARRAY object containing all cells of a precise subset of the GeoRaster object (as specified by a rectangular window or a clipping polygon geometry, layer or band numbers, and pyramid level). This BLOB object or SDO_NUMBER_ARRAY object contains only raster cells and no related metadata.

• SDO_GEOR.getRasterData creates a single BLOB object containing all cells of the GeoRaster object at a specified pyramid level. This BLOB object contains only raster cells and no related metadata.

• SDO_GEOR.getRasterBlocks returns an object that includes all image data inside or touching a specified window. Specifically, it returns an object of the SDO_RASTERSET collection type that identifies all blocks of a specified pyramid level that are inside or touch a specified window.

• SDO_GEOR.reproject not only transforms a whole GeoRaster object from one projected coordinate system to another, but can also include the same capability as SDO_GEOR.getRasterSubset by directly transforming the query result into a different coordinate system on-the-fly.

• SDO_GEOR.rectify performs reprojection, rectification, or orthorectification on all or part of a georeferenced GeoRaster object based on a query window. The resulting object can be a new GeoRaster object (for persistent storage) or a BLOB (for temporary use).

• SDO_GEOR_RA.findCells generates a new GeoRaster object based on the cell values using the GeoRaster Raster Algebra language. (See Cell Value-Based Conditional Queries for more information.)

• SDO_GEOR_AGGR.mosaicSubset mosaics a number of GeoRaster objects into one GeoRaster object.

• SDO_GEOR_AGGR.getMosaicSubset lets you query a virtual mosaic and returns a mosaicked subset on-the-fly.

• SDO_GEOR.getBitmapMask, SDO_GEOR.getBitmapMaskSubset, SDO_GEOR.getBitmapMaskValue, and SDO_GEOR.getBitmapMaskValues let you query bitmap masks on the basis of a full raster, a window, or single cells.

There are two types of raster updates: space-based and cell value-based

• Space-based raster update allows you update a GeoRaster object's raster data inside a specified window entirely using either a single value or another GeoRaster object.

  To update or change the value of raster cells in a specified window to a single value, you can use the SDO_GEOR.changeCellValue procedure. To change the value of raster cells specified by row/column arrays or by a multipoint geometry to new values, you can use the SDO_GEOR.changeCellValuesprocedure. You can call the SDO_GEOR.updateRaster procedure to update a specified pyramid of a specified area, or the overlapping parts of one GeoRaster object, with a specified pyramid and specified bands or layers of another GeoRaster object. Both the SDO_GEOR.changeCellValue and the SDO_GEOR.updateRaster procedures support all pyramid levels, including the original raster data (that is, pyramid level 0).

  The SDO_GEOR_AGGR.append procedure can also be used to update an existing image with a new image (see Image Appending).

• Cell value-based raster update allows you update a GeoRaster object's raster data based on the cell values using the GeoRaster Raster Algebra language.

  SDO_GEOR_RA.rasterUpdate selects cells from the specified GeoRaster object based on Boolean strings specified in the conditions parameter, and updates corresponding cell values by calculating expression strings specified in the vals parameter. Both the conditions and vals parameters can be complicated expressions using the raster algebra language. (See Cell Value-Based Conditional Updates (Edits) for more information.)

If statistics are already set in the GeoRaster object when you perform space-based or raster cell value-based updates, the statistics are not removed or updated automatically after you run the raster update procedures. If necessary, you should remove or regenerate the statistics.

Note:

If you use any procedure that adds or overwrites data in the input GeoRaster object, you should make a copy of the original GeoRaster object and use the procedure on the copied object. After you are satisfied with the result of the procedure, you can discard the original GeoRaster object if you wish.

If you want to change the raster data table name, the attributes of a GeoRaster object, or any other metadata, see the recommendations, requirements, and restrictions noted in Querying and Updating GeoRaster Metadata.

After updating a GeoRaster object's metadata or cell data (or both) and before you commit a database transaction, you should call the SQL UPDATE statement to update the GeoRaster object (see Updating GeoRaster Objects Before Committing).