postgresql postgis如果点在圆内 [英] postgresql postgis If point inside circle

问题描述

我正在使用PostgreSQL作为数据库，我有一个名为car_wash的表，其字段为"point geometry"(使用postgis)，所以在应用程序中，我正在使用GOOGLE API从用户那里得到长期支持，下一步，我需要在周围创建圆圈用户，并检查我是否在此圈子内使用car_wash

I'm using postgresql as db , i have the table named car_wash with field "point geometry"(use postgis) so in application I'm getting lon lat from user using GOOGLE API, next step I need to create circle around user and check if car_wash inside this circle I use

  select *
 from car_wash cw
where
ST_DWithin (
   cw.lon_lat,
   ST_GeomFromText('POINT(54.21 22.54)')
)=false
AND
not cw.was_deleted

这是核心方式吗?如果需要，根据此查询，我的srid为0

Is it corect way? IF you need my srid is 0 according to this query

 Select Find_SRID('public',  'car_wash',  'lon_lat')

推荐答案

ST_GeomFromText('POINT(54.21 22.54)')的SRID必须与cw.lon_lat的SRID相同.假设cw.lon_lat的SRID为4326，则可以使用ST_GeomFromText('POINT(54.21 22.54)'，4326)设置其他属性srib. 其次，ST_DWithin需要缓冲区距离作为第三个参数.因此，假设您要检查点是否在100米缓冲区内，应该是

SRID of the ST_GeomFromText('POINT(54.21 22.54)') must be same as the SRID of cw.lon_lat. Suppose SRID of cw.lon_lat is 4326 you can set the other attribute srib by using ST_GeomFromText('POINT(54.21 22.54)',4326). Secondly, ST_DWithin needs buffer distance as 3rd parameter. So suppose if you want to check if point is within 100 meter buffer it should be like

ST_DWithin (
   cw.lon_lat,
   ST_GeomFromText('POINT(54.21 22.54)', 3857), 100
)

缓冲区值取决于srid单位.如果是3857米您需要使用st_setSRID例如将cw.lon_lat和POINT(54.21 22.54)转换为相同的SRID，以使其正常工作.

Buffer value is according to the srid unit. in case of 3857 its meter. You need to convert cw.lon_lat and POINT(54.21 22.54) to the same SRID in order to make this work, using st_setSRID e.g.

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