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geospatial - 球面几何和地理上的 ST_Intersect 有什么区别？

问题描述

我遇到了一种特殊情况，我试图找到（部分）位于多边形中的任何地理空间对象。当我使用WGS84 SRIDST_Intersect在两个几何图形上应用该函数时，多边形和多边形以北的点的交集按预期返回：FALSE

SELECT ST_Intersects(
    ST_GeomFromText('POLYGON((-12 0,12 0,12 50.7,-12 50.7,-12 0))', 4326), 
    ST_GeomFromText('POINT(6.0 50.9)', 4326)
);


现在，当我运行相同的查询时，查询返回的是两个地理而不是几何TRUE：

SELECT ST_Intersects( 
    ST_GeogFromText('POLYGON((-12 0,12 0,12 50.7,-12 50.7,-12 0))'),
    ST_GeogFromText('POINT(6 50.9)')
);

我希望地理版本使用最短的大圆距离来创建多边形，而几何版本在平面上创建多边形，然后才将其投影到WGS84椭圆上。

有人可以验证或揭穿我的怀疑吗？

我正在使用 PostGis 2.4.4 运行 postgresql 9.6

标签： geospatialpostgis

解决方案

Operations on geography data type are done over a sphere. Operations on geometry data type are done over a plane.

The shortest line joining two points on a plane is a straight line.

The shortest line joining two points on a sphere is an arc. This arc is called the great circle arc and is build by intersecting the sphere with a plan going through the 2 points and the center of the earth.

Consequently, the arc going through -12;50.7N and +12;50.7N with pass through a point near 0;51.3N. This holds true for lines but also for polygon boundaries.

This doc has some interesting graphics to understand the concepts behind the geography type

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