PostGIS 1.5.1 Manual222 / 315

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.16

This function supports 3d and will not drop the z-index.

Examples

--Get estimate of infected area based on point observationsSELECT d.disease_type,ST_ConvexHull(ST_Collect(d.the_geom)) As the_geomFROM disease_obs As dGROUP BY d.disease_type;

Convex Hull of a MultiLinestring and a MultiPoint seen together with the MultiLinestring and MultiPoint

SELECT ST_AsText(ST_ConvexHull(ST_Collect(ST_GeomFromText(’MULTILINESTRING((100 190,10 8),(150 10, 20 30))’),ST_GeomFromText(’MULTIPOINT(50 5, 150 30, 50 10, 10 10)’))) );

---st_astext--POLYGON((50 5,10 8,10 10,100 190,150 30,150 10,50 5))

See Also

ST_Collect, ST_MinimumBoundingCircle

7.9.5 ST_CurveToLine

Name

ST_CurveToLine – Converts a CIRCULARSTRING/CURVEDPOLYGON to a LINESTRING/POLYGON

PostGIS 1.5.1 Manual223 / 315

Synopsis

geometry ST_CurveToLine(geometry curveGeom);geometry ST_CurveToLine(geometry curveGeom, integer segments_per_qtr_circle);

Description

Converst a CIRCULAR STRING to regular LINESTRING or CURVEPOLYGON to POLYGON. Useful for outputting to de-vices that can’t support CIRCULARSTRING geometry types

Converts a given geometry to a linear geometry. Each curved geometry or segment is converted into a linear approximation usingthe default value of 32 segments per quarter circle

Availability: 1.2.2?

This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.7

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT ST_AsText(ST_CurveToLine(ST_GeomFromText(’CIRCULARSTRING(220268 150415,220227 ←↩150505,220227 150406)’)));

--Result --LINESTRING(220268 150415,220269.95064912 150416.539364228,220271.823415575 ←↩

150418.17258804,220273.613787707 150419.895736857,220275.317452352 150421.704659462,220276.930305234 150423.594998003,220278.448460847 ←↩

150425.562198489,220279.868261823 150427.60152176,220281.186287736 150429.708054909,220282.399363347 ←↩

150431.876723113,220283.50456625 150434.10230186,220284.499233914 150436.379429536,220285.380970099 ←↩

150438.702620341,220286.147650624 150441.066277505,220286.797428488 150443.464706771,220287.328738321 150445.892130112,220287.740300149 ←↩

150448.342699654,220288.031122486 150450.810511759,220288.200504713 150453.289621251,220288.248038775 ←↩

150455.77405574,220288.173610157 150458.257830005,220287.977398166 150460.734960415,220287.659875492 ←↩

150463.199479347,220287.221807076 150465.64544956,220286.664248262 150468.066978495,220285.988542259 ←↩

150470.458232479,220285.196316903 150472.81345077,220284.289480732 150475.126959442,220283.270218395 150477.39318505,220282.140985384 ←↩

150479.606668057,220280.90450212 150481.762075989,220279.5637474 150483.85421628,220278.12195122 ←↩

150485.87804878,220276.582586992 150487.828697901,220274.949363179 150489.701464356,220273.226214362 ←↩

150491.491836488,220271.417291757 150493.195501133,220269.526953216 150494.808354014,220267.559752731 ←↩

150496.326509628,220265.520429459 150497.746310603,220263.41389631 150499.064336517,220261.245228106 ←↩

150500.277412127,220259.019649359 150501.38261503,220256.742521683 150502.377282695,220254.419330878 ←↩

150503.259018879,