如何用坐标和方位角在PostGis中建立扇形楔(扇形)？
如何用坐标和方位角在PostGis中建立扇形楔(扇形)？
提问于 2022-07-20 11:45:07
我找不到正确的答案，试图在PostGis中创建函数，该函数返回几何类型的多边形。该函数可用于在地图上可视化蜂窝网络拓扑结构。下面你可以找到PostGis的这个函数，它有下一个输入参数: lon，lat，方位，距离，宽度。馅饼的距离长度；馅饼的宽度。
create or replace function sector_3(lon float, lat float, azimuth float, distance integer, width integer)
returns geometry
language plpgsql
as
$$
declare
sector geometry;
begin
sector = ST_MakePolygon(ST_MakeLine(ARRAY[ST_SetSRID(ST_MakePoint(lon,lat),4326),
ST_Project(ST_SetSRID(ST_MakePoint(lon,lat),4326)::geography, distance, pi()*(azimuth-(width/2))/180.0)::geometry,
ST_Project(ST_SetSRID(ST_MakePoint(lon,lat),4326)::geography, distance, pi()*(azimuth-(width/2-1*(width/2/5)))/180.0)::geometry,
ST_Project(ST_SetSRID(ST_MakePoint(lon,lat),4326)::geography, distance, pi()*(azimuth-(width/2-2*(width/2/5)))/180.0)::geometry,
ST_Project(ST_SetSRID(ST_MakePoint(lon,lat),4326)::geography, distance, pi()*(azimuth-(width/2-3*(width/2/5)))/180.0)::geometry,
ST_Project(ST_SetSRID(ST_MakePoint(lon,lat),4326)::geography, distance, pi()*(azimuth-(width/2-4*(width/2/5)))/180.0)::geometry,
ST_Project(ST_SetSRID(ST_MakePoint(lon,lat),4326)::geography, distance, pi()*(azimuth)/180.0)::geometry,
ST_Project(ST_SetSRID(ST_MakePoint(lon,lat),4326)::geography, distance, pi()*(azimuth+(width/2-4*(width/2/5)))/180.0)::geometry,
ST_Project(ST_SetSRID(ST_MakePoint(lon,lat),4326)::geography, distance, pi()*(azimuth+(width/2-3*(width/2/5)))/180.0)::geometry,
ST_Project(ST_SetSRID(ST_MakePoint(lon,lat),4326)::geography, distance, pi()*(azimuth+(width/2-2*(width/2/5)))/180.0)::geometry,
ST_Project(ST_SetSRID(ST_MakePoint(lon,lat),4326)::geography, distance, pi()*(azimuth+(width/2-1*(width/2/5)))/180.0)::geometry,
ST_Project(ST_SetSRID(ST_MakePoint(lon,lat),4326)::geography, distance, pi()*(azimuth+(width/2))/180.0)::geometry,
ST_SetSRID(ST_MakePoint(lon,lat),4326)
]));
return sector;
end;
$$;因此，您将看到扇区，它从给定的点(龙，lat)和给定的距离(长度)和宽度开始。
回答 2
Stack Overflow用户
回答已采纳
发布于 2022-07-22 12:29:55
您可以通过首先使用distance、lon和lat参数创建缓冲区来稍微简化一些事情，这样您就已经有了想要的内容。第二步是删除所需缓冲区的一部分，您可以使用ST_Split完成这一操作。函数ST_Split需要一个几何和一个刀片来切割几何，这个刀片可以根据缓冲区的中心点(参考坐标对)、azimuth和distance创建为一个LineString，使用ST_Project。此时，您有两个几何图形--您想要的区域和缓冲区的其余部分--因此您可以使用ST_GeometryN只返回您感兴趣的区域：
WITH j (geom,azimuth,distance,width) AS (
VALUES (ST_SetSRID(ST_MakePoint(38.94,45.05),4326),90,120,40)
)
SELECT
ST_GeometryN(
ST_Split(
ST_Buffer(geom::geography,distance)::geometry,
ST_MakeLine(ARRAY[
ST_Project(geom,distance+1,radians(azimuth-(width/2)))::geometry, geom,
ST_Project(geom,distance+1,radians(azimuth+(width/2)))::geometry]
)
),2)
FROM j;
演示：db<>fiddle
为了更好地说明所提出的解决方案，下一个查询将在三个不同的CTE中描述缓冲区、投影点和基于它们创建的刀片。
WITH
original_values (geom,azimuth,distance,width) AS (
VALUES (ST_SetSRID(ST_MakePoint(38.94,45.05),4326),90,120,40)),
points (array_points) AS (
SELECT ARRAY[
ST_Project(geom,distance+1,radians(azimuth-(width/2)))::geometry, geom,
ST_Project(geom,distance+1,radians(azimuth+(width/2)))::geometry]
FROM original_values),
line (blade) AS (
SELECT ST_MakeLine(array_points)
FROM points),
area (buffer) AS (
SELECT ST_Buffer(geom::geography,distance)
FROM original_values
)
SELECT buffer FROM area
UNION
SELECT unnest(array_points) FROM points
UNION
SELECT blade FROM line;
Stack Overflow用户
发布于 2022-10-06 06:09:45
create or replace function sector_make(lon float, lat float, azimuth float, distance integer, width integer)
returns geometry
language plpgsql
as
$$
declare
sector geometry;
i integer;
begin
sector = ST_SetSRID(ST_MakePoint(lon,lat),4326);
for i in (select 0-width/2)..(select width/2)
loop
sector=ST_UNION(sector,ST_Project(ST_SetSRID(ST_MakePoint(lon,lat),4326)::geography, distance, radians(azimuth+i))::geometry);
end loop;
return ST_MakePolygon(ST_MakeLine(ARRAY[sector,ST_SetSRID(ST_MakePoint(lon,lat),4326)]));
end;
$$;页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/73051042
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