Bigquery - 给定一个地理点和距离如何在它周围获得一个多边形

Question

我有一个问题要解决，在给定中心地理点和距离的情况下，我需要在它周围提取一个多边形。

想象一下任何地理点：比如说：41.6748248，-83.6882749，我需要用 50 米的距离在它周围找到一个八边形，例如

回答我自己的问题，因为我没有找到任何其他可以直接在 BQ 中使用的方法。 （到目前为止，BQ 中还没有针对此的原生函数。）

Answer 1

CREATE TEMPORARY FUNCTION get_point_at_a_distance(latitude float64, longitude float64, d int64, brng int64) as (
    (select ST_GEOGPOINT(((longitude* (ACOS(-1)/180)) + atan2(sin(brng* (ACOS(-1)/180))*sin(d/6371000)*cos(latitude* (ACOS(-1)/180)),cos(d/6371000)-sin(latitude* (ACOS(-1)/180))*sin(latitude* (ACOS(-1)/180))))* (180/ACOS(-1)), 
    (asin(sin(latitude* (ACOS(-1)/180))*cos(d/6371000) + cos(latitude* (ACOS(-1)/180))*sin(d/6371000)*cos(brng* (ACOS(-1)/180))))* (180/ACOS(-1))))
); 

CREATE TEMPORARY FUNCTION get_polygon(latitude float64, longitude float64, distance int64) as (

(select ST_MAKEPOLYGON(ST_MAKELINE(ARRAY_AGG(geo_point))) 
from 
(
select get_point_at_a_distance(latitude, longitude, distance, 0) as geo_point union all 
select get_point_at_a_distance(latitude, longitude, distance, 45) as geo_point  union all 
select get_point_at_a_distance(latitude, longitude, distance, 90) as geo_point  union all 
select get_point_at_a_distance(latitude, longitude, distance, 135) as geo_point  union all 
select get_point_at_a_distance(latitude, longitude, distance, 180) as geo_point  union all 
select get_point_at_a_distance(latitude, longitude, distance, 225) as geo_point  union all 
select get_point_at_a_distance(latitude, longitude, distance, 270) as geo_point  union all 
select get_point_at_a_distance(latitude, longitude, distance, 315) as geo_point 
)));

select get_polygon(41.6748248, -83.6882749, 50)```


Confirm with: https://www.keene.edu/campus/maps/tool/
Try to plot the output: 
-83.6887005865171, 41.6751427574177
 -83.6888769116458, 41.6748247984293
 -83.6887005865171 ,41.6745068410117
 -83.6882749, 41.674375139197
 -83.6878492134828, 41.6745068410116
 -83.6876728883542, 41.6748247984293
-83.6878492134828, 41.6751427574177
 -83.6882749, 41.675274460803
 -83.6887005865171, 41.6751427574177