使用最近邻法在 PostGIS 中绘制一条线

Question

这是我发送到 PostGIS 邮件列表的电子邮件中的交叉帖子

到目前为止，我一直在努力在一个点和它的投影之间创建一条线 位置在一条线上已经很长了，但我快到了。截至昨天，和 在包括任何最近邻分析之前，我得到的结果显示在 这张图片：

如您所见，粉红色的每个点都连接到所有投影点，而我只想将每个粉红色 x 连接到其各自的投影。

在 IRC 上，建议我使用 BostonGIS's nearest neighbor method。我将函数输入到 PostgreSQL 并尝试失败，如下所述。我假设我的错误是由于错误的参数类型造成的。我对此进行了尝试，将某些列的类型更改为 varchar，但仍然无法正常工作。

关于我做错了什么有什么想法吗？关于如何解决它的任何建议？

代码：

-- this sql script creates a line table that connects points 

-- convert multi lines into lines

CREATE TABLE exploded_roads AS
SELECT the_geom
FROM (
    SELECT ST_GeometryN(
    the_geom,
    generate_series(1, ST_NumGeometries(the_geom)))
    AS the_geom 
    FROM "StreetCenterLines"
)
AS foo;


-- Create line table that'll connect the centroids to the projected points on exploded lines
CREATE TABLE lines_from_centroids_to_roads (
    the_geom    geometry,
    edge_id SERIAL
);

-- Populate Table
INSERT INTO lines_from_centroids_to_roads ( the_geom )
SELECT
    ST_MakeLine(
        centroids.the_geom,
        (pgis_fn_nn(centroids.the_geom, 1000000, 1,1000, 'exploded_roads' ,'true', 'gid',
            ST_Line_Interpolate_Point(
                exploded_roads.the_geom,
                ST_Line_Locate_Point(
                    exploded_roads.the_geom,
                    centroids.the_geom
                )
            )
        )).*
    )
FROM exploded_roads, fred_city_o6_da_centroids centroids;

DROP TABLE exploded_roads;

错误

NOTICE:  CREATE TABLE will create implicit sequence "lines_from_centroids_to_roads_edge_id_seq" for serial column "lines_from_centroids_to_roads.edge_id"

ERROR:  function pgis_fn_nn(geometry, integer, integer, integer, unknown, unknown, unknown, geometry) does not exist
LINE 28:   (pgis_fn_nn(centroids.the_geom, 1000000, 1,1000, 'exploded...
            ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.


********** Error **********

ERROR: function pgis_fn_nn(geometry, integer, integer, integer, unknown, unknown, unknown, geometry) does not exist
SQL state: 42883
Hint: No function matches the given name and argument types. You might need to add explicit type casts.
Character: 584

Answer 1

一个问题是我认为该函数需要second argument (distguess) to be a double precision 而不是整数。尝试 1000000.0 或尝试强制转换为明确浮动...

Answer 2

事实证明，我根本不需要使用最近邻。我分配了一个与我连接线的质心相同的 id

-- this sql script creates a line table that connects points 

-- delete existing tables if they exist
DROP TABLE exploded_roads;
DROP TABLE projected_points;
DROP TABLE lines_from_centroids_to_roads;


-- convert multi lines into lines
CREATE TABLE exploded_roads (
    the_geom    geometry,
    edge_id     serial
);

-- insert the linestring that don't need to be converted
INSERT INTO exploded_roads
SELECT the_geom
FROM "StreetCenterLines"
WHERE st_geometrytype(the_geom) = 'ST_LineString';


INSERT INTO exploded_roads
SELECT the_geom
FROM (
    SELECT ST_GeometryN(
    the_geom,
    generate_series(1, ST_NumGeometries(the_geom)))
    AS the_geom 
    FROM "StreetCenterLines"
)
AS foo;





-- create projected points table with ids matching centroid table
CREATE TABLE projected_points (
    the_geom    geometry,
    pid     serial,
    dauid       int
);


-- Populate Table
INSERT INTO projected_points(the_geom, dauid)
SELECT DISTINCT ON ("DAUID")
    ( 
        ST_Line_Interpolate_Point(
            exploded_roads.the_geom,
            ST_Line_Locate_Point(
                exploded_roads.the_geom,
                centroids.the_geom
            )
        )
    ),
    (centroids."DAUID"::int)

FROM exploded_roads, fred_city_o6_da_centroids centroids;


-- Create Line tables
CREATE TABLE lines_from_centroids_to_roads (
    the_geom    geometry,
    edge_id SERIAL
);


-- Populate Line Table
INSERT INTO lines_from_centroids_to_roads(
SELECT
    ST_MakeLine( centroids.the_geom, projected_points.the_geom )
FROM projected_points, fred_city_o6_da_centroids centroids
WHERE projected_points.dauid = centroids."DAUID"::int
);

-- Delete temp tables
--DROP TABLE exploded_roads;
--DROP TABLE projected_points;