SDO_UTIL.TILE_GEOMETRY

Format

SDO_UTIL.TILE_GEOMETRY(
  geom                   IN SDO_GEOMETRY,
  x_axis_min             IN NUMBER,
  x_axis_max             IN NUMBER,
  y_axis_min             IN NUMBER,
  y_axis_max             IN NUMBER,
  tile_resolution        IN NUMBER,
  resolution_factor      IN NUMBER   := 0,
  perform_intersection   IN VARCHAR2 := 'TRUE',
  compute_percent        IN VARCHAR2 := 'FALSE',
  geodetic_tolerance     IN NUMBER   := .05)
  RETURN mdsys.tile_geom_table_type DETERMINISTIC
         PIPELINED PARALLEL_ENABLE;

Description

Tiles a geometry based on the specified tile resolution and resolution factor. Returns MDSYS.TILE_GEOM_TABLE_TYPE, which is a table of MDSYS.TILE_GEOM_TYPE objects.

Parameters

geom

Geometry to tile.

x_axis_min

Minimum value along the x-axis for tiling domain. (See the Usage Notes for more information.)

x_axis_max

Maximum value along the x-axis for tiling domain. (See the Usage Notes for more information.)

y_axis_min

Minimum value along the y-axis for tiling domain. (See the Usage Notes for more information.)

y_axis_max

Maximum value along the y-axis for tiling domain. (See the Usage Notes for more information.)

tile_resolution

Tile size value. (See the Usage Notes for more information.)

resolution_factor

A value factor applied to the tile_resolution parameter.

Default value is 0. (See the Usage Notes for more information.)

perform_intersection

A string value of TRUE (the default) clips boundary tiles to the geometry boundary.

A string value of FALSE returns full tiles along the geometry boundary.

compute_percent

The default string value is FALSE.

A string value of TRUE computes the value between 0 and 1. To compute this value perform_intersection must also be set to TRUE.

geodetic_tolerance

Default is 0.05.

This parameter is only used if the geometry to tile is longitude/latitude. The default value can be overridden with a value smaller than 0.05.

Usage Notes

The SDO_UTIL.TILE_GEOMETRY function can be used to:

• Tile geometries, for example, farm plots or land parcels

• Tile geometries with the tiles that coincide with the cells of a raster.

  For raster cell sized tiles, use the extent of the raster as the tiling domain, and set the tile_resolution to the raster resolution.

This function returns a table of type MDSYS.TILE_GEOM_TABLE_TYPE, which is defined as follows:

CREATE OR REPLACE TYPE mdsys.tile_geom_table_type AS TABLE OF tile_geom_type;

The object type MDSYS.TILE_GEOM_TYPE, used in the preceding code, is defined as follows:

CREATE OR REPLACE TYPE mdsys.tile_geom_type AS OBJECT (
  tile_id      NUMBER,
  status       CHAR,
  percent      NUMBER,
  tile_center  SDO_GEOMETRY,
  geom         SDO_GEOMETRY);

The parameters used to define the object type, MDSYS.TILE_GEOM_TYPE are:

• tile_id: A unique number assigned to each tile, beginning with 1.

• status: The value can be either:

  • 'I': for interior tile

  • 'B': for boundary tile on the geometry

• percent: Percent of tile area coincident with geometry area. Value between 0 and 1. Interior tiles will always return 1.

• tile_center: Center point of the tile.

• geom: A geometry tile. If the parameter perform_intersection is TRUE, boundary tiles are clipped to the geometry boundary.

The parameters, x_axis_min, x_axis_max, y_axis_min and y_axis_max used in the SDO_UTIL.TILE_GEOMETRY function, represent the tiling domain. The tiling domain is an extent that contains all the geometries that are required to tile. For example, for longitude/latitude geometries, a tiling domain can be specified using the following parameter values:

• x_axis_min: -180

• x_axis_max: 180

• y_axis_min: -90

• y_axis_max: 90 Also note, if the same tiling domain is specified when tiling more than one geometry, common tiles are generated when geometries overlap.

The tile_resolution and resolution_factor parameters influence the tile size as highlighted in the following:

• The desired tile size value is determined by the tile_resolution parameter. For example, for a value 5, tiles will be 5x5 or a factor of 5x5 if the parameter resolution_factor is not 0.

• resolution_factor, when specified, applies a factor to the tile_resolution parameter, to tile a geometry with either smaller or larger tiles than tile_resolution.

  The following table describes the tile size as determined by the resolution_factor values:

  Resolution Factor Value	Tile Size
  0 (the default)	No factor is applied. Tiles size are driven by the tile_resolution parameter. See Example-1 for more information.
  > 0	Tiles generated will be a factor smaller relative to the tile_resolution parameter. For example, for the following resolution_factor values: 1: tile size is 1/4 smaller than tile_resolution 2: tile size is 1/16 smaller than tile_resolution 3: tile size is 1/64 smaller than tile_resolution See Example-2 for more information.
  < 0	Tiles generated will be a factor larger relative to the tile_resolution parameter. For example, for the following resolution_factor values: -1: tile size is 4 times larger than tile_resolution -2: tile size is 16 times larger than tile_resolution -3: tile size is 64 times larger than tile_resolution See Example-3 for more information.

  However, when generating tiles, smaller tiles will be fully contained by larger tiles. Also, tiles generated with different resolutions, larger or smaller, will always be aligned.

Examples

The following examples tile geometries with the tiles that coincide with the cells of a raster. Also, the raster extent is projected (not longitude, latitude), so the domain extent is set to the extent of the raster. The parameter, perform_intersection => 'TRUE' in the examples, causes clipping of the boundary tiles to the boundary of the farm.

Example 1

This example tiles a farm geometry with tiles that are equal to the size of a raster cell. The resolution of the raster is 1000, so tiles will be 1000x1000

WITH
  part0 AS (SELECT b.tile_id,
                   b.status,
                   b.percent,
                   b.tile_center,
                   b.geom
            FROM farm_plots a,
            TABLE (sdo_util.tile_geometry(geom                 => a.geom,
                                          x_axis_min           => 272039.5,
                                          x_axis_max           => 275188.5,
                                          y_axis_min           => 370575.5,
                                          y_axis_max           => 380165.5,
                                          tile_resolution      => 1000,
                                          resolution_factor    => 0,
                                          perform_intersection => 'TRUE',
                                          compute_percent      => 'TRUE',
                                          geodetic_tolerance   => NULL)) b
            WHERE a.id = -1)
 SELECT tile_id, geom FROM part0 ORDER BY tile_id;

The following figure depicts the resulting output:

Figure: Tile size same astile_resolution

Description of the illustration tile_geometry_same_tile_size.png

Example 2

The following example tiles a farm geometry with tiles that are 1/4 times smaller than 1000 x 1000, because resolution_factor => 1 is specified.

WITH
  part0 AS (SELECT b.tile_id,
                   b.status,
                   b.percent,
                   b.tile_center,
                   b.geom
            FROM farm_plots a,
            TABLE (sdo_util.tile_geometry(geom                 => a.geom,
                                          x_axis_min           => 272039.5,
                                          x_axis_max           => 275188.5,
                                          y_axis_min           => 370575.5,
                                          y_axis_max           => 380165.5,
                                          tile_resolution      => 1000,
                                          resolution_factor    => 1,
                                          perform_intersection => 'TRUE',
                                          compute_percent      => 'TRUE',
                                          geodetic_tolerance   => NULL)) b
            WHERE a.id = -1)
 SELECT tile_id, geom FROM part0 ORDER BY tile_id;

The following figure depicts the resulting output:

Figure: Tile size smaller thantile_resolution

Description of the illustration tile_geometry_small_tile_size.png

Example 3

The following example tiles a farm geometry with tiles that are 4 times greater than 1000 x 1000, because resolution_factor => -1 is specified.

WITH
  part0 AS (SELECT b.tile_id,
                   b.status,
                   b.percent,
                   b.tile_center,
                   b.geom
            FROM farm_plots a,
            TABLE (sdo_util.tile_geometry(geom                 => a.geom,
                                          x_axis_min           => 272039.5,
                                          x_axis_max           => 275188.5,
                                          y_axis_min           => 370575.5,
                                          y_axis_max           => 380165.5,
                                          tile_resolution      => 1000,
                                          resolution_factor    => -1,
                                          perform_intersection => 'TRUE',
                                          compute_percent      => 'TRUE',
                                          geodetic_tolerance   => NULL)) b
            WHERE a.id = -1)
 SELECT tile_id, geom FROM part0 ORDER BY tile_id;

The following figure depicts the resulting output:

Figure: Tile size greater thantile_resolution

Description of the illustration tile_geometry_big_tile_size.png