如何计算 PostGIS 中离线串最近的点?
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【中文标题】如何计算 PostGIS 中离线串最近的点?【英文标题】:How to calculate nearest point to a linestring in PostGIS? 【发布时间】:2016-06-21 05:15:16 【问题描述】:我正在关注question 来计算最接近道路的 POI(线串)。我能够计算线串中的最近点,但我无法找到从 POI 到线串上最近点(顶点)的距离。
这是我查找最近 POI 的代码。
CREATE TABLE road(id serial PRIMARY KEY, the_geog geography(LINESTRING,4326) );
CREATE TABLE poi(gid serial PRIMARY KEY, name varchar, city varchar, the_geog geography(POINT,4326) )
值是:
INSERT INTO road (id, the_geog) VALUES (123, ST_GeographyFromText('SRID=4326;LINESTRING(85.280194 23.296728,85.281572 23.297479)') );
计算最近点:
SELECT
poi.name,
poi.city,
ST_AsTEXT(poi.the_geog),
ST_Distance(road.the_geog, poi.the_geog)/1000.0 AS distance_km,
ST_AsTEXT(road.the_geog::geometry)
FROM road, poi
WHERE
road.id = 123
AND ST_DWithin(road.the_geog, poi.the_geog, 10000.0)
ORDER BY
ST_LineLocatePoint(road.the_geog::geometry, poi.the_geog::geometry),
ST_Distance(road.the_geog, poi.the_geog)
;
如果线串是这样表示的:[85.280194 23.296728,85.281572 23.297479]
,我想要这样的结果:
poi vertex distance_km
85.280194 23.296728 85.280001 23.299876 3
85.289673 23.291987 85.281572 23.297479 5
【问题讨论】:
【参考方案1】:使用ST_DumpPoints()提取直线的顶点:
SELECT id,the_geog, (ST_dumppoints(road.the_geog::GEOMETRY)).geom AS vertex FROM road;
您必须将 GEOGRAPHY 转换为 GEOMETRY,否则 st_dumppoints 不起作用。
您的整个查询可能如下所示:
SELECT road.id AS road_id,
ST_Astext(poi.the_geog) AS poi,
ST_astext(road.vertex) AS vertex,
ST_AsText(road.the_geog) AS line,
ST_Distance(vertex, poi.the_geog) AS distance
FROM (SELECT id,the_geog, (ST_dumppoints(road.the_geog::GEOMETRY)).geom AS vertex
FROM road
) as road,
poi
WHERE road.id = 123
ORDER by ST_Distance(vertex, poi.the_geog);
【讨论】:
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