确定最小边界圆的半径或直径 [英] Determining the radius or diameter of a Minimum Bounding Circle

问题描述

如果我有一个类似于以下查询的 MBC:

If I have an MBC that looks like the following query:

SELECT ST_AsText(ST_MinimumBoundingCircle(geom)::geometry) AS Circle
FROM "Regions"

我想知道如何轻松确定它的半径.我已经求助于找到圆的质心，此时我可以尝试计算 MBC 中返回的多边形中的一个点与质心之间的距离，但是我似乎无法从多边形中只抓取一个顶点.

I'm wondering how I can easily determine it's radius. I've resorted to finding the centroid of the circle, at which point I can attempt to calculate the distance between one of the points in the MBCs returned polygon against the centroid however I can't seem to grab just one vertex from the polygon.

谢谢.

推荐答案

ST_MinimumBoundingCircle 是一个用户贡献的函数，源代码是用 PL/pgSQL 编写的.您可以

ST_MinimumBoundingCircle is a user-contributed function with source written in PL/pgSQL. You can modify the source as a renamed function ST_MinimumBoundingRadius(inputgeom geometry) with these modifications:

• 只需要一个参数 inputgeom geometry
• 将返回类型(靠近顶部)从 geometry 更改为 double precision
• 对于 POINT 类型，将 RETURN hull; 更改为 RETURN 0;
• 删除接近末尾的ST_Buffer 语句，并返回radius.

• Only needs one argument inputgeom geometry
• Change return type (near top) from geometry to double precision
• For POINT types, change RETURN hull; to RETURN 0;
• Remove the ST_Buffer statement near the end, and just return the radius.

应该很容易.请注意，该算法存在一些问题，例如 ticket #2996.

Should be easy. Be aware there are some problems with the algorithm, such as ticket #2996.

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