UCOSP code sprint day #2
Saturday, January 16, 2010

Today we continue to explore the unanswered questions left over from yesterday. These are the things that I have explored

OGC stands for opengeospatial consortium, and GEOS is an implementation of the OGC specification. It is formed by a set of companies who have invested their time to have set out a standard for geospatial information systems and databases. GEOS implements part of the SFS standard and Ingres uses it for geospatial manipulation and calculation. The patch Alex sent sends me extends GEOS to support more of the standard so that Ingres can use the GEOS.

Functions instances to implement:

  • IsSimple,
  • IsEmpty,
  • Overlaps,
  • X(on points only),
  • Y(on points only),
  • NumPoints (on linestring only)

Files to change:
  • adgoptab.roc
  • fi_defn.txt
  • aduint.h
  • adfops.h
  • adupoint.c
  • adffiids.h


Following the standard that is quoted from OpenGIS Implementation Specification for Geographic information - Simple feature access:
Organization: Open Geospatial Consortium Inc.
Date: 2005-11-22
Reference number of this document: OGC 05-134
Version: 1.1.0
Category: OpenGIS® Implementation Specification
Editor: Keith Ryden

SQL functions on type Geometry
IsEmpty(g Geometry) : Integer
The return type is Integer, with a return value of 1 for TRUE, 0 for FALSE, and –1 for UNKNOWN corresponding to a function invocation on NULL arguments.
TRUE if this geometric object corresponds to the empty set

IsSimple(g Geometry): Integer
The return type is Integer, with a return value of 1 for TRUE, 0 for FALSE, and –1 for UNKNOWN corresponding to a function invocation on NULL arguments.
TRUE if this geometric object is simple, as defined in the Geometry Model

SQL functions that test spatial relationships
Overlaps(g1 Geometry, g2 Geometry) : Integer
The return type is Integer, with a return value of 1 for TRUE, 0 for FALSE, and –1 for UNKNOWN corresponding to a function invocation on NULL arguments.
TRUE if the intersection of g1 and g2 results in a value of the same dimension as g1 and g2 that is different from both g1 and g2 Integer

SQL functions on type Point
X(p Point) : Double Precision
return the x-coordinate of Point p as a double precision number

Y(p Point) : Double Precision
return the y-coordinate of Point p as a double precision number

SQL functions on type LineString
NumPoints(l LineString) : Integer
return the number of Points in the LineString

Posted byA nerdy girl at 12:23 PM  

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