説明

ジオメトリを完全に含む最小の円ポリゴンを返します。

The circle is approximated by a polygon with a default of 48 segments per quarter circle. Because the polygon is an approximation of the minimum bounding circle, some points in the input geometry may not be contained within the polygon. The approximation can be improved by increasing the number of segments, with little performance penalty. For applications where a polygonal approximation is not suitable, ST_MinimumBoundingRadius may be used.

しばしば、MULTI系とジオメトリコレクションで使用します。しかし、集約関数ではありません。ST_Collectと併用して、ジオメトリの集合の最小包含円を得ます。ST_MinimumBoundingCircle(ST_Collect(somepointfield))とします。

ポリゴンの面積を最小包含円の面積で割った割合は、しばしばRoeckテストとして参照されます。

Availability: 1.4.0 - GEOSが必要です。

関連情報

ST_Collect, ST_MinimumBoundingRadius

例

SELECT d.disease_type,
        ST_MinimumBoundingCircle(ST_Collect(d.the_geom)) As the_geom
        FROM disease_obs As d
        GROUP BY d.disease_type;

ポイントとラインストリングの最小包含円です。4分の1円の近似に8区分使用しています。

SELECT ST_AsText(ST_MinimumBoundingCircle(
                ST_Collect(
                        ST_GeomFromEWKT('LINESTRING(55 75,125 150)'),
                                ST_Point(20, 80)), 8
                                )) As wktmbc;
wktmbc
-----------
POLYGON((135.59714732062 115,134.384753327498 102.690357210921,130.79416296937 90.8537670908995,124.963360620072 79.9451031602111,117.116420743937 70.3835792560632,107.554896839789 62.5366393799277,96.6462329091006 56.70583703063,84.8096427890789 53.115246672502,72.5000000000001 51.9028526793802,60.1903572109213 53.1152466725019,48.3537670908996 56.7058370306299,37.4451031602112 62.5366393799276,27.8835792560632 70.383579256063,20.0366393799278 79.9451031602109,14.20583703063 90.8537670908993,10.615246672502 102.690357210921,9.40285267938019 115,10.6152466725019 127.309642789079,14.2058370306299 139.1462329091,20.0366393799275 150.054896839789,27.883579256063 159.616420743937,
37.4451031602108 167.463360620072,48.3537670908992 173.29416296937,60.190357210921 176.884753327498,
72.4999999999998 178.09714732062,84.8096427890786 176.884753327498,96.6462329091003 173.29416296937,107.554896839789 167.463360620072,
117.116420743937 159.616420743937,124.963360620072 150.054896839789,130.79416296937 139.146232909101,134.384753327498 127.309642789079,135.59714732062 115))
                                

関連情報

ST_Collect, ST_MinimumBoundingRadius