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All Blog Articles, Data Models and Free Source Code by Simon Greener, The SpatialDB Advisor is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

Function to round ordinates of a SQL Server Spatial geometry object

Tuesday January 03 2012 at 06:08

Keywordsround ordinate coordinate tolerance geometry SQL Server Spatial

The presented function allows a user to round the ordinates of a Sql Server Spatial geometry object to the user’s understood geometric precision.

The result of many geoprocessing operations in any spatial type can be geometries with ordinates (X, Y etc) that have far more decimal digits of precision than the initial geometry.

I present here a simple function STRoundGeometry that takes a geometry object and some specifications of the precision of any X, Y, Z or M ordinates, applies those specifications to the geometry and returns the corrected geometry.

STRoundGeometry calls STMove which is described in a related article

  1. USE [GISDB] -- Change this to your database
  2. GO
  3. -- Drop if exists
  4. --
  5. DROP FUNCTION dbo.STRoundGeometry;
  6. -- Now create
  7. --
  8. CREATE FUNCTION dbo.STRoundGeometry(@p_geometry geometry,
  9.                                     @p_round_x   INT = 3,
  10.                                     @p_round_y   INT = 3,
  11.                                     @p_round_z   INT = 2,
  12.                                     @p_round_m   INT = 2)
  13. RETURNS geometry
  14. AS
  15. BEGIN
  16.   DECLARE
  17.     @v_geom geometry;
  18.   BEGIN
  19.     IF ( @p_geometry IS NULL )
  20.       RETURN @p_geometry;
  21.     SET @v_geom = dbo.STMove(@p_geometry,0.0,0.0,0.0,0.0,@p_round_x,@p_round_y,@p_round_z,@p_round_m);
  22.   END;
  23.   RETURN @v_geom;
  24. END;
  25. GO

Testing this we get.

  1. SELECT dbo.STRoundGeometry(geometry::STGeomFromText('MULTIPOLYGON (((160 400, 200.00000000000088 400.00000000000045, 200.00000000000088 480.00000000000017, 160 480, 160 400)), ((100 200, 180.00000000000119 300.0000000000008, 100 300, 100 200)))',0),
  2.                            2,2,1,1).STAsText() AS geom;

Which results in:

MULTIPOLYGON (((160 400, 200 400, 200 480, 160 480, 160 400)), ((100 200, 180 300, 100 300, 100 200)))

I hope this is useful to someone.

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