Postgres - 使用 postgis 计算距离
Postgres - Calculate distance with postgis
找了几天，试了所有的东西，我来问一下如何用PostGis在Postgres上计算两点之间的距离。我得到了一个 table 调用位置。这 table 得到了点类型的“坐标”列。当用户在应用程序中插入一个值时，我需要获取按关闭距离排序的位置。我知道我需要使用 ST_Distance，但每次我尝试使用坐标点时我都做不到。我需要以公里为单位的结果。
我试试：
SELECT ST_Distance('POINT(0.0 0.0)', ST_GeomFromText(location.coordenate)) FROM app.location as location;
要获得 metres/kilometres 中的距离，您需要将坐标转换为以米为单位的 SRS，或者如果可能，使用 geography 而不是 geometry，因为 ST_Distance returns两个geography参数的距离，单位为米（1km=1000m），例如
SELECT
ST_Distance(ST_MakePoint(0.0,0.0)::geography, coordenate::geography)/1000
FROM app.location;
正在将 geometry / text 转换为 geography
演示：db<>fiddle
CREATE TABLE location (gid int, coordenate geometry(point,4326));
INSERT INTO location VALUES
(1,'SRID=4326;POINT(10 10)'),(2,'SRID=4326;POINT(0.1 0.1)');
SELECT
gid, ST_AsText(coordenate),
ST_Distance(ST_MakePoint(0.0,0.0)::geography, coordenate::geography)/1000
FROM location
ORDER BY coordenate::geography <-> ST_MakePoint(0.0,0.0)::geography;
gid | st_astext | ?column?
-----+----------------+--------------------
2 | POINT(0.1 0.1) | 15.690343289660001
1 | POINT(10 10) | 1565.1090992178902
(2 rows)
运算符<->表示距离，因此在ORDER BY子句上使用它可以按距离对结果集进行排序。
正在将 point 转换为 geography
数据类型 point 不是 PostGIS 数据类型，而是来自 PostgreSQL 的 geometric data type。为了使用 ST_Distance，您必须将点转换为几何或地理。
演示：db<>fiddle
CREATE TABLE location (gid int, coordenate point);
INSERT INTO location VALUES
(1,point(10,10)),(2,point(0.1,0.1));
SELECT *,
ST_Distance(
ST_MakePoint(0.0,0.0)::geography,
ST_MakePoint(coordenate[0],coordenate[1])::geography)/1000
FROM location
ORDER BY ST_MakePoint(coordenate[0],coordenate[1])::geography <-> ST_MakePoint(0.0,0.0)::geography;
gid | coordenate | ?column?
-----+------------+--------------------
2 | (0.1,0.1) | 15.690343289660001
1 | (10,10) | 1565.1090992178902
(2 rows)
延伸阅读：
找了几天，试了所有的东西，我来问一下如何用PostGis在Postgres上计算两点之间的距离。我得到了一个 table 调用位置。这 table 得到了点类型的“坐标”列。当用户在应用程序中插入一个值时，我需要获取按关闭距离排序的位置。我知道我需要使用 ST_Distance，但每次我尝试使用坐标点时我都做不到。我需要以公里为单位的结果。
我试试：
SELECT ST_Distance('POINT(0.0 0.0)', ST_GeomFromText(location.coordenate)) FROM app.location as location;
要获得 metres/kilometres 中的距离，您需要将坐标转换为以米为单位的 SRS，或者如果可能，使用 geography 而不是 geometry，因为 ST_Distance returns两个geography参数的距离，单位为米（1km=1000m），例如
SELECT
ST_Distance(ST_MakePoint(0.0,0.0)::geography, coordenate::geography)/1000
FROM app.location;
正在将 geometry / text 转换为 geography
演示：db<>fiddle
CREATE TABLE location (gid int, coordenate geometry(point,4326));
INSERT INTO location VALUES
(1,'SRID=4326;POINT(10 10)'),(2,'SRID=4326;POINT(0.1 0.1)');
SELECT
gid, ST_AsText(coordenate),
ST_Distance(ST_MakePoint(0.0,0.0)::geography, coordenate::geography)/1000
FROM location
ORDER BY coordenate::geography <-> ST_MakePoint(0.0,0.0)::geography;
gid | st_astext | ?column?
-----+----------------+--------------------
2 | POINT(0.1 0.1) | 15.690343289660001
1 | POINT(10 10) | 1565.1090992178902
(2 rows)
运算符<->表示距离，因此在ORDER BY子句上使用它可以按距离对结果集进行排序。
正在将 point 转换为 geography
数据类型 point 不是 PostGIS 数据类型，而是来自 PostgreSQL 的 geometric data type。为了使用 ST_Distance，您必须将点转换为几何或地理。
演示：db<>fiddle
CREATE TABLE location (gid int, coordenate point);
INSERT INTO location VALUES
(1,point(10,10)),(2,point(0.1,0.1));
SELECT *,
ST_Distance(
ST_MakePoint(0.0,0.0)::geography,
ST_MakePoint(coordenate[0],coordenate[1])::geography)/1000
FROM location
ORDER BY ST_MakePoint(coordenate[0],coordenate[1])::geography <-> ST_MakePoint(0.0,0.0)::geography;
gid | coordenate | ?column?
-----+------------+--------------------
2 | (0.1,0.1) | 15.690343289660001
1 | (10,10) | 1565.1090992178902
(2 rows)
延伸阅读：