$centerSphere（查询谓词运算操作符）

定义

$centerSphere

Defines a circle for a geospatial query that uses spherical geometry. The query returns documents that are within the bounds of the circle. You can use the $centerSphere operator on both GeoJSON objects and legacy coordinate pairs.

To use $centerSphere, specify an array that contains:

• 圆中心点的网格坐标，以及

• 以弧度为单位测量的圆的半径。要计算弧度，请参阅将距离转换为球面弧度操作符。

{
   <location field>: {
      $geoWithin: { $centerSphere: [ [ <x>, <y> ], <radius> ] }
   }
}

重要

如果使用经度和纬度，请先指定经度。

行为

Applications can use $centerSphere without having a geospatial index. However, geospatial indexes support much faster queries than the unindexed equivalents.

Both 2dsphere and 2d geospatial indexes support $centerSphere.

例子

以下示例查询网格坐标并返回经度 88 W 和纬度 30 N 的 10 英里半径内的所有文档。该查询通过除以近似地球赤道半径 3963.2 英里，将距离转换为弧度：

db.places.find( {
  loc: { $geoWithin: { $centerSphere: [ [ -88, 30 ], 10/3963.2 ] } }
} )