最短路径实现

不念不忘少年蓝@ 2022-07-14 20:00 163阅读 0赞

**主要工具**

1.  QGIS建立拓扑关系
2.  Postgres存储数据表
3.  Geoserver发布相关服务

#### QGIS建立拓扑关系 ####

使用v.clean运行，并用DBManager即可以建立拓扑关系并导入数据库。

**注意**  
QGIS2.16有数据溢出问题，使用QGIS2.14可以解决这个问题

#### Postgres存储数据表 ####

导入wuhan\_road\_topo后可以进行相应处理

drop table if exists tmp_pts_topo;
    create table tmp_pts_topo
    as
    select 
    osm_id
    ,(st_dump(geom)).geom as geom
    ,st_startpoint((st_dump(geom)).geom)
    ,st_endpoint((st_dump(geom)).geom)
    ,st_length((st_dump(geom)).geom)*110 as dis
    from wuhan_road_topo;
    
    alter table tmp_pts_topo add column id serial;
    select * from tmp_pts_topo limit 10;
    
    drop table if exists tmp_pts;
    create table tmp_pts(geom geometry);
    
    insert into tmp_pts
    select geom from
    (
    select st_startpoint as geom from tmp_pts_topo 
    union all 
    select st_endpoint  as geom from tmp_pts_topo
    )x
    group by geom;
    
    
    alter table tmp_pts add column id serial; 
    
    select * from tmp_pts limit 10;
    select * from tmp_pts_topo limit 10;
    alter table tmp_pts_topo add column start_point int;
    alter table tmp_pts_topo add column end_point int;
    
    create index indx_geom_tmp_pts on tmp_pts 
    using gist(geom);
    
    create index indx_geom_tmp_pts_1 on tmp_pts_topo 
    using gist(st_startpoint);
    
    create index indx_geom_tmp_pts_2 on tmp_pts_topo 
    using gist(st_endpoint);
    
    
    select * from tmp_pts limit 10;
    select * from tmp_pts_topo limit 10;
    
    update tmp_pts_topo t1 set start_point=t2.id
    from tmp_pts t2
    where st_dwithin(t1.st_startpoint,t2.geom,0);
    
    update tmp_pts_topo t1 set end_point=t2.id
    from tmp_pts t2
    where st_dwithin(t1.st_endpoint,t2.geom,0);
    
    insert into tmp_pts(geom)
    select st_startpoint 
    from tmp_pts_topo 
    where start_point is null
    union
    select st_endpoint 
    from tmp_pts_topo 
    where end_point is null;
    
    
    update tmp_pts_topo t1 set start_point=t2.id
    from tmp_pts t2
    where st_dwithin(t1.st_startpoint,t2.geom,0)
    and start_point is null;
    
    update tmp_pts_topo t1 set end_point=t2.id
    from tmp_pts t2
    where st_dwithin(t1.st_endpoint,t2.geom,0)
    and end_point is null;
    
    delete from tmp_pts_topo where id in
    (
    select id from(
    select id,row_number() 
    over(partition by start_point,end_point order by dis) 
    from tmp_pts_topo
    where (start_point,end_point) in
    (
    select start_point,end_point
    from tmp_pts_topo 
    group by start_point,end_point
    having count(*)>1
    )
    )x
    where row_number>1
    );
    
    select *
    from tmp_pts_topo 
    where start_point=1138 and end_point=1143;
    
    select count(*) from tmp_pts_topo;
    
    select * from tmp_pts_topo limit 1;
    
    select * from tmp_pts_topo where start_point=10997;
    
    delete from tmp_pts_topo where start_point is null or end_point is null;

**注意**  
要删除空白点，不然无法正常运行

**测试查询**  
选定一个起点与终点，测试有没有结果

with start_point as
    (
    select st_setsrid(
    st_makepoint(114.25,30.57)
    ,4326) as p
    )
    ,end_point as
    (
    select st_setsrid(st_makepoint(114.23,30.56),4326) as p
    )
    select t2.seq,st_asgeojson(t1.geom) from 
    (
    SELECT seq, 
    id1 AS node, 
    id2 AS edge, 
    cost FROM pgr_dijkstra('
    SELECT id,                        
    start_point as source,                        
    end_point as target,                        
    dis AS cost                       
    FROM tmp_pts_topo',                
    (
    select id from tmp_pts
    where st_dwithin(
    (select p from start_point)
    ,geom,0.05)
    order by st_distance(
    (select p from start_point)
    ,geom)
    limit 1
    )
    , 
    (
    select id from tmp_pts
    where st_dwithin(
    (select p from end_point)
    ,geom,0.05)
    order by st_distance(
    (select p from end_point)
    ,geom)
    limit 1
    ), false, false)
    )t2 left join tmp_pts_topo t1
    on t1.id=t2.edge
    where t2.edge>0
    order by t2.seq;

#### Geoserver发布相关服务 ####

使用Geoserver连接postgres并发布wuhan\_road\_topo，并配置新的SQL视图，SQL视图可以接收参数返回相应的视图

可参见：[GeoServer的SQL Views详解][GeoServer_SQL Views]

将SQL语句修改为

with start_point as
    (
    select st_setsrid(
    st_makepoint(%startLon%,%startLat%)
    ,4326) as p
    )
    ,end_point as
    (
    select st_setsrid(st_makepoint(%endLon%,%endLat%),4326) as p
    )
    select t2.seq,(t1.geom) from 
    (
    SELECT seq, 
    id1 AS node, 
    id2 AS edge, 
    cost FROM pgr_dijkstra('
    SELECT id,                        
    start_point as source,                        
    end_point as target,                        
    dis AS cost                       
    FROM tmp_pts_topo',                
    (
    select id from tmp_pts
    where st_dwithin(
    (select p from start_point)
    ,geom,0.05)
    order by st_distance(
    (select p from start_point)
    ,geom)
    limit 1
    )
    , 
    (
    select id from tmp_pts
    where st_dwithin(
    (select p from end_point)
    ,geom,0.05)
    order by st_distance(
    (select p from end_point)
    ,geom)
    limit 1
    ), false, false)
    )t2 left join tmp_pts_topo t1
    on t1.id=t2.edge
    where t2.edge>0
    order by t2.seq

发布成功后可以通过修改参数，如[http://localhost:8080/geoserver/wuhanwork/wms?service=WMS&version=1.1.0&request=GetMap&view&layers=wuhan:tt&styles=&bbox=114.22769686949,30.559729927104,114.246243846172,30.5719569775606&width=512&height=337&srs=EPSG:4326&format=application/openlayers&viewparams=startLon:114.25;startLat:30.57;endLon:114.39;endLat:30.70][http_localhost_8080_geoserver_wuhanwork_wms_service_WMS_version_1.1.0_request_GetMap_view_layers_wuhan_tt_styles_bbox_114.22769686949_30.559729927104_114.246243846172_30.5719569775606_width_512_height_337_srs_EPSG_4326_format_application_openlayers_viewparams_startLon_114.25_startLat_30.57_endLon_114.39_endLat_30.70] 来访问  
即可通过输入起点与终点，返回最短路径

![p6.png_raw_true][]

**客户端实现**

<!DOCTYPE html>
    <html lang="zh-cmn-Hans">
    
    <head>
        <meta charset="UTF-8">
        <meta http-equiv="X-UA-Compatible" content="IE=Edge">
        <meta name="viewport" content="initial-scale=1.0, user-scalable=no, width=device-width">
        
        <link rel="stylesheet" href="http://cdn.bootcss.com/bootstrap/3.3.0/css/bootstrap.min.css">
        
        <link rel="stylesheet" href="http://cdn.bootcss.com/bootstrap/3.3.0/css/bootstrap-theme.min.css">
        <link rel="stylesheet" href="./css/prism.css" type="text/css">
        <link rel="stylesheet" href="./css/ol.css" type="text/css">
        <link rel="stylesheet" href="./css/layout.css" type="text/css">
        <link rel="stylesheet" href="./css/popup.css">
        <link rel="stylesheet" type="text/css" href="./css/main.css">
        <script src="js/ol-debug.js"></script>
        <script src="js/ol-deps.js"></script>
        <script src="js/ol.js"></script>
        <title>HomeWork</title>
    </head>
    
    <body>
        <div class="mycontainer">
            <div class="row" id="header">
                <h1>Digital engineering practice</h1>
            </div>
        </div>
        <div class="container-fluid">
            <div class="row-fluid">
                <div class="span12">
                    <div id="map" class="map"></div>
                    <div id="popup" class="ol-popup">
                        <a href="#" id="popup-closer" class="ol-popup-closer"></a>
                        <div id="popup-content"></div>
                    </div>
                    
                    <div class="buttonlay">
                        <button type="button" id="btStart" onclick="btStart_click()" data-original-title="Click" class="btn btn-lg btn-default btn-check mybutton"><span>Click to input start point</span></button>
                        <button type="button" id="btEnd" onclick="btEnd_click()" data-original-title="Click" class="btn btn-lg btn-default btn-check mybutton"><span>Click to input end point</span> </button>
                        <button type="button" id="selectShort" onclick="select_click()" data-original-title="Click" class="btn btn-lg btn-default btn-check mybutton"> <span>Click to slect shortest way</span></button>
                    </div>
                </div>
            </div>
        </div>
    </body>
    <script type="text/javascript">
    /**
     * Elements that make up the popup.
     */
    var container = document.getElementById('popup');
    var content = document.getElementById('popup-content');
    var closer = document.getElementById('popup-closer');
    
    //记录按钮动作
    var ableSt = false;
    var ableEd = false;
    
    //起点经度，起点维度，终点经度，终点纬度
    var st_lon, st_lat, ed_lon, ed_lat;
    
    
    /**
     * Create an overlay to anchor the popup to the map.
     */
    var overlay = new ol.Overlay( /** @type {olx.OverlayOptions} */ ({
        element: container,
        autoPan: true,
        autoPanAnimation: {
            duration: 250
        }
    }));
    
    /**
     * 加载瓦片图层
     **/
    var source = new ol.source.XYZ({
        url: 'http://localhost:8080/tilemill/{z}/{x}/{y}.png'
    });
    
    var center = ol.proj.transform([114.2207, 30.5960], 'EPSG:4326', 'EPSG:3857');
    var map = new ol.Map({
        logo: false,
        layers: [
            new ol.layer.Tile({
                source: source
            })
        ],
        overlays: [overlay],
        target: 'map',
        view: new ol.View({
            maxZoom: 18,
            center: center,
            zoom: 10
        })
    });
    
    
    
    /**
     * Add a click handler to hide the popup.
     * @return {boolean} Don't follow the href.
     */
    closer.onclick = function() {
         
        overlay.setPosition(undefined);
        closer.blur();
        return false;
    };
    
    
    /**
     * Add a click handler to the map to render the popup.
     */
    map.on('singleclick', function(evt) {
         
        var coordinate = evt.coordinate;
        var hdms = ol.coordinate.toStringHDMS(ol.proj.transform(
            coordinate, 'EPSG:3857', 'EPSG:4326'));
        var xy = ol.proj.transform(coordinate, 'EPSG:3857', 'EPSG:4326').toString();
        var lon_string = xy.split(",")[0];
        var lat_string = xy.split(",")[1];
    
        var lon_number = new Number(lon_string);
        var lat_number = new Number(lat_string);
    
        if (ableSt) {
            st_lon = lon_number.toFixed(4);
            st_lat = lat_number.toFixed(4);
            content.innerHTML = '<p>You put start point here:</p><code>' + hdms + '</code>';
            ableSt = false;
        } else {
            if (ableEd) {
                ed_lon = lon_number.toFixed(4);
                ed_lat = lat_number.toFixed(4);
                content.innerHTML = '<p>You put end point here:</p><code>' + hdms + '</code>';
                ableEd = false;
            } else {
                content.innerHTML = '<p>You clicked here:</p><code>' + hdms + '</code>';
            }
        }
    
        overlay.setPosition(coordinate);
    });
    
    /**
     *按钮相应事件
     **/
    function btStart_click() {
         
        ableSt = true;
    }
    
    function btEnd_click() {
         
        ableEd = true;
    }
    
    //最短路径按钮
    function select_click() {
         
        overlay.setPosition(undefined);
        closer.blur();
    
        var getwayurl = 'http://localhost:8080/geoserver/wuhan/ows?service=WFS&version=1.0.0&request=GetFeature&typeName=wuhan:wuhan&maxFeatures=50&outputFormat=application/json&viewparams=' + 'st_lon:' + st_lon + ';st_lat:' + st_lat + ';ed_lon:' + ed_lon + ';ed_lat:' + ed_lat;
        var getMywayurl = 'http://localhost:8080/geoserver/wuhanwork/ows?service=WFS&version=1.0.0&request=GetFeature&typeName=wuhanwork:tt&maxFeatures=50&outputFormat=application/json&viewparams=' + 'startLon:' + st_lon + ';startLat:' + st_lat + ';endLon:' + ed_lon + ';endLat:' + ed_lat;
    
        var roadsource = new ol.layer.Vector({
            source: new ol.source.Vector({       
                url: getMywayurl,
                format: new ol.format.GeoJSON({
                    extractStyles: true
                }),
                style: new ol.style.Style({
                    stroke: new ol.style.Stroke({
                        color: [255, 255, 255, 1],
                        width: 30
                    })
                })
            })
        });
    
        map.addLayer(roadsource);
    }
    </script>
    
    </html>

**源代码:**[SourceCode][]

![p7.png][]

[GeoServer_SQL Views]: http://blog.csdn.net/freeland1/article/details/49737793
[http_localhost_8080_geoserver_wuhanwork_wms_service_WMS_version_1.1.0_request_GetMap_view_layers_wuhan_tt_styles_bbox_114.22769686949_30.559729927104_114.246243846172_30.5719569775606_width_512_height_337_srs_EPSG_4326_format_application_openlayers_viewparams_startLon_114.25_startLat_30.57_endLon_114.39_endLat_30.70]: http://localhost:8080/geoserver/wuhanwork/wms?service=WMS&version=1.1.0&request=GetMap&view&layers=wuhan:tt&styles=&bbox=114.22769686949,30.559729927104,114.246243846172,30.5719569775606&width=512&height=337&srs=EPSG:4326&format=application/openlayers&viewparams=startLon:114.25;startLat:30.57;endLon:114.39;endLat:30.70
[p6.png_raw_true]: /images/20220715/fa2042b1bc864c669f66cd59086b72b5.png
[SourceCode]: https://github.com/whuhan2013/mywebproject/tree/master/DigitalEnginn
[p7.png]: https://raw.githubusercontent.com/whuhan2013/myImage/master/R/p7.png