ST_MINIMUMBOUNDINGCIRCLE

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功能描述

返回包含几何图形的最小圆形多边形。

语法格式

GEOMETRY ST_MINIMUMBOUNDINGCIRCLE(GEOMETRY geomA, INTEGER num_segs_per_qt_circ=48);

参数说明

• geomA：目标 MULTILINEGEOMETRYSTRING 对象。
• num_segs_per_qt_circ：四分之一圆做等分弧段的个数。可选，默认：48。

函数返回类型

GEOMETRY 类型

使用说明

1. 边界圆近似为多边形，默认情况下每四分之一圆有 48 个线段。
2. 由于多边形是最小外接圆的近似值，因此输入几何中的某些点可能不包含在多边形内。 可以通过增加分段数量来改进近似值。
3. 与 ST_Collect 一起使用以获得一组几何图形的最小边界圆。
4. 要计算位于最小圆（最大直径）上的两个点，请使用ST_LongestLine。
5. 多边形的面积除以最小包含圆的面积之比称为 REOCK 紧致度得分。
6. 此函数是由 GEOS 模块执行的。

示例

点和线串的最小外接圆。 用8段近似四分之一圆：

SQL> SELECT ST_AsText(ST_MinimumBoundingCircle(
             ST_Collect(
                 ST_GeomFromText('LINESTRING(55 75,125 150)'),
                     ST_Point(20, 80)), 8
                     )) As wktmbc;

+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     WKTMBC                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| POLYGON((72.5 178.4024474346694,84.8692038866403 177.18418718546332,96.76306620464648 173.5762234960138,107.72451249529236 167.71720838753708,117.33230052487836 159.83230052487838,125.21720838753708 150.22451249529237,131.0762234960138 139.26306620464646,134.68418718546332 127.3692038866403,135.9024474346694 115,134.68418718546332 102.63079611335971,131.0762234960138 90.73693379535354,125.2172083875371 79.77548750470766,117.33230052487836 70.16769947512164,107.72451249529236 62.282791612462916,96.76306620464648 56.42377650398619,84.86920388664032 52.815812814536685,72.50000000000001 51.59755256533059,60.13079611335969 52.815812814536685,48.236933795353536 56.42377650398618,37.27548750470765 62.28279161246291,27.667699475121637 70.16769947512162,19.78279161246292 79.77548750470764,13.923776503986206 90.7369337953535,10.31581281453669 102.63079611335968,9.097552565330588 114.99999999999999,10.315812814536683 127.3692038866403,13.923776503986199 139.2630662046465,19.782791612462905 150.22451249529234,27.667699475121626 159.83230052487835,37.275487504707634 167.71720838753708,48.23693379535349 173.5762234960138,60.13079611335967 177.18418718546332,72.49999999999999 178.4024474346694)) |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

(1 row)