[英]Postgres - Calculate distance with postgis
After looking for days, and try all what I find, I'm here to ask how to calculate the distance beetwen two points on Postgres with PostGis.在寻找了几天并尝试了所有我发现的东西之后,我在这里询问如何使用 PostGis 计算 Postgres 上两点之间的距离。 I got a table called location.
我有一张名为 location 的表。 This table got a column "coordenate" of type point.
该表有一个点类型的列“coordenate”。 When the user inserts a value on the application I need to get the locations ordered by the closes distance.
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。 I know I need to use ST_Distance, but everytime I try to cast the POINT of coordenate I can't.
我知道我需要使用 ST_Distance,但每次我尝试投射坐标点时我都做不到。 I need the result in Km.
我需要以公里为单位的结果。
I try:我尝试:
SELECT ST_Distance('POINT(0.0 0.0)', ST_GeomFromText(location.coordenate)) FROM app.location as location;
To get distances in metres/kilometres you need to either transform your coordinates to a SRS that has metre as unit or, if possible, use geography
instead of geometry
, as ST_Distance
returns the distance of two geography
parameters in metres (1km = 1000m), eg要获得以米/公里为单位的距离,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
返回两个以米为单位的geography
参数的距离(1km = 1000m),例如
SELECT
ST_Distance(ST_MakePoint(0.0,0.0)::geography, coordenate::geography)/1000
FROM app.location;
geometry
/ text
to geography
geometry
/ text
转换为geography
Demo: db<>fiddle
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)
The operator <->
means distance, so using it on the ORDER BY
clause you can order the result set by distance.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。
point
to geography
point
到geography
The data type point
is not a PostGIS data type, but a geometric data type
from PostgreSQL. In order to use ST_Distance
you have to cast the points to either geometry or 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。
Demo: db<>fiddle
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)
Further reading:延伸阅读:
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