Question

这是我发送到PostGIS邮件列表的电子邮件的交叉帖子

到目前为止，我努力在一个点和它的预测之间创建一条线在一条线上的位置已经很长但我几乎就在那里。截至昨天，和在包括任何最近邻居分析之前，我得到的结果显示在这张图片：

QGis screenshot

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

在IRC上，我建议使用BostonGIS's nearest neighbor method。我向PostgreSQL输入了这个函数并尝试了它，如下所述。我假设我的错误是由于错误的参数类型。我玩了一下，把一些列的类型更改为varchar，但我仍然无法让它工作。

关于我做错的任何想法？有关如何修复它的任何建议吗？

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

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或尝试强制转换为浮动...

Answer 2

事实证明我毕竟不需要使用最近的邻居。我分配了一个与我通过

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;

使用最近邻方法在PostGIS中绘制一条线

2 个答案: