Oracle7 Spatial Data Option User's Guide and Reference

Geometry Functions

This chapter contains descriptions of the following geometric functions and procedures:

Table 6¯1 Geometric Functions:

Function Description
SDO_GEOM.ADD_NODES

Stores points in the geometry table.

SDO_GEOM.INIT_ELEMENT

Initializes space in the geometry table for a new object.

SDO_GEOM.INTERACT

Determines if two objects are disjoint.

SDO_GEOM.RELATE

Determines how two objects interact.

SDO_GEOM.VALIDATE_GEOMETRY

Determines if a geometry is legal.

SDO_GEOM.ADD_NODES

Purpose

This procedure stores coordinate geometry points into the SDOGEOM table.

Syntax

SDO_GEOM.ADD_NODES (layername, SDO_GID, SDO_ESEQ, SDO_ETYPE, X-ord1,Y-ord1[,...,X125, Y125])

Keywords and Parameters

layername

Specifies the name of the data set layer. The layername is used to construct the name of the geometry and spatial index tables. Datatype is VARCHAR2.

SDO_GID

Specifies the unique geometric object identifier. Datatype is NUMBER.

SDO_ESEQ

Specifies the element sequence number. The eseq is unique within an SDO_GID. Datatype is NUMBER.

SDO_ETYPE

Specifies the type of geometric element. Datatype is INTEGER, corresponding to the following constants:
1 SDO_GEOM.POINT_TYPE
2 SDO_GEOM.LINESTRING_TYPE
3 SDO_GEOM.POLYGON_TYPE

X ordinateN,
Y ordinateN

Specifies the X and Y values of a vertex (coordinate pair) in a geometry. Up to 125 pairs may be added in a single call. Datatype is NUMBER.

Returns

Usage Notes

Use the SQL CREATE TABLE command to create the geometry table, <layername>_SDOGEOM, before calling this procedure.
Prior to calling this procedure, call the SDO_GEOM.INIT_ELEMENT() function to initialize the geometry element and retrieve the element sequence number (SDO_ESEQ).
Close a polygon by providing the coordinates of the first vertex as the last vertex.
Call this procedure iteratively with the same GID to add coordinates to a geometric object. You can add up to 125 coordinate pairs on each call, and there is no limit to how many times you can add more vertices.
This procedure cannot be used when <layername>_SDOGEOM is a view.

Example 6¯1

The following example adds polygon element for geometry 25 in the LAYER1 data set. The polygon is a square:

SQL> EXECUTE SDO_GEOM.ADD_NODES (`LAYER1', 25,

2> SDO_GEOM.POLYGON_TYPE,

Related Topics

SDO_GEOM.INIT_ELEMENT() function

SDO_GEOM.INIT_ELEMENT

Purpose

This function initializes elements in the SDOINFO table or view for a new geometry element.

Syntax

SDO_GEOM.INIT_ELEMENT (layername, SDO_GID)

Keywords and Parameters

layername

Specifies the name of the data set layer. The layername is used to construct the name of the geometry and spatial index tables. Datatype is VARCHAR2.

SDO_GID

Specifies the geometric object identifier. Datatype is NUMBER.

Returns

This function returns the next element sequence number. The datatype is INTEGER.

Usage Notes

Consider the following when using this function:

This function initializes the element to be stored, but does not actually insert coordinates into the SDOGEOM table. The SDO_GEOM.ADD_NODES() procedure is used to insert associated coordinate data.

Related Topics

SDO_GEOM.ADD_NODES() procedure

SDO_GEOM.INTERACT

Purpose

This function determines if two geometric objects interact.

Syntax

SDO_GEOM.INTERACT (layername1, SDO_GID1, [layername2,] SDO_GID2)

SDO_GEOM.INTERACT (layername1, SDO_GID1, X_tolerance, Y_tolerance, X_ordinateN, Y_ordinateN [, ..., X125, Y125])

Keywords and Parameters

layername1,
layername2

Specifies the name of the data set layer. The layername is used to construct the name of the geometry and spatial index tables. Datatype is VARCHAR2.

SDO_GID1,
SDO_GID2

Specifies the geometric object identifier. Datatype is NUMBER.

X_tolerance,
Y_tolerance

Specifies the distance two points can be apart and still be considered the same due to rounding errors. Tolerance must be greater than zero. If you want zero tolerance, enter a number such as 0.000005, where the number of decimal digits matches the precision of your data.

X_ordinateN,
Y_ordinateN

Specifies the X and Y values of a vertex (coordinate pair) in a geometry. Up to 125 pairs may be specified. Datatype is NUMBER.

Returns

This function returns "TRUE" if the first and second objects interact with each other and are not disjoint. Datatype is VARCHAR2.

Usage Notes

Related Topics

SDO_GEOM.RELATE() procedure

SDO_GEOM.RELATE

Purpose

This function examines two geometric objects to determine their spatial relationship.

Syntax

SDO_GEOM.RELATE (layername1, SDO_GID1, mask, [layername2,] SDO_GID2)

SDO_GEOM.RELATE (layername1, SDO_GID1, mask, X_tolerance, Y_tolerance, X_ordinateN, Y_ordinateN, [,...,X125, Y125])

Keywords and Parameters

layername1,
layername2

Specifies the name of the data set layer. The layername is used to construct the name of the geometry and spatial index tables. Datatype is VARCHAR2.

SDO_GID1,
SDO_GID2

Specifies the geometric object identifier. Datatype is NUMBER.

mask

Specifies the relationship mask. See the list of keywords in the Usage section.

X_tolerance,
Y_tolerance

Specifies the distance two points can be apart and still be considered the same due to rounding errors. Tolerance must be greater than zero. If you want zero tolerance, enter a number such as 0.000005, where the number of decimal digits matches the precision of your data.

X_ordinateN,
Y_ordinateN

Specifies the X and Y values of a vertex (coordinate pair) in a geometry. Up to 125 pairs may be specified. Datatype is NUMBER.

Returns

The SDO_GEOM.RELATE procedure can return three types of answers:

If you pass a mask listing one or more relationships, the procedure returns the names of the relationships if all of them are true. If one or more relationships are false, the procedure returns FALSE. Datatype is VARCHAR2.
If you pass the DETERMINE keyword in the mask, the procedure returns the one relationship keyword which best matches the geometries.
If you pass the ANYINTERACT keyword in the mask, the procedure returns either TRUE or FALSE. This is equivalent to the SDO_GEOM.INTERACT procedure.

Usage Notes

The following relationships can be tested:

ANYINTERACT - Returns true if the objects are not disjoint.
CONTAINS - Returns true if the second object is entirely within the first object and the object boundaries do not touch.
COVEREDBY - Returns true if the first object is entirely within the second object and the object boundaries touch at one or more points.
COVERS - Returns true if the second object is entirely within the first object and the boundaries touch in one or more places.
DISJOINT - Returns true if the objects have no common boundary or interior points.
EQUAL - Returns true if the objects share every point of their boundaries and interior, including any holes in the objects.
INSIDE - Returns true if the first object is entirely within the second object and the object boundaries do not touch.
OVERLAPBDYDISJOINT - Returns true if the object overlap, and their boundaries intersect in one or more places.
OVERLAPBDYINTERSECT - Returns true if the objects overlap, but their boundaries do not interact.
TOUCH - Returns true if the two objects share a common boundary point, but no interior points.

Related Topics

SDO_GEOM.INTERACT() procedure

SDO_GEOM.VALIDATE_GEOMETRY

Purpose

This function provides a consistency check for legal geometry types. The function checks the representation of the geometry from the tables against the element definitions.

Syntax

SDO_GEOM.VALIDATE_GEOMETRY (layername,SDO_GID)

Keywords and Parameters

layername

Specifies the name of the data set layer. The layername is used to construct the name of the geometry and spatial index tables. Datatype is VARCHAR2.

SDO_GID

Specifies the geometric object identifier. Datatype is NUMBER.

Returns

This function returns "TRUE" if the geometry is legal. Datatype is VARCHAR2.

Usage Notes

Consider the following when using this function:

This function checks for the following:

polygons have at least three points and must be closed
polygons cannot have crossing line segments (as in a bow-tie)
for complex polygons, subelements are wholly contained within the outermost polygon
line strings must have at least two points

Related Topics

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