Web GIS离线解决方案

2023-07-23 17:50:58

1、背景

在离线环境下（局域网中）的GIS系统中如何使用地图？这里的地图主要指的是地图底图，有了底图切片数据，我们就可以看到地图，在上面加上自己的业务数据图层，进行相关操作。

要在离线环境下看到GIS地图，就要有底图切片数据，地图的底图切片数据在一定时间内是不会变化的，可以使用一些地图下载器下载地图切片，如这个地图下载器。

在CS系统中可以基于GMap.Net来做，参考《百度谷歌离线地图解决方案》。

下面介绍下Web系统如何使用GIS切片数据，开发web GIS系统。

2、使用GeoWebCache发布WMS服务

Geowebcache是基于Java的Web开源项目，主要用于缓存各种WMS数据源的地图瓦片，它实现了多种服务接口，包括WMS-C，WMTS，TMS，KML。

Geowebcache作为一个独立的开源项目，在最近被Geosever的几个版本所集成，主要是对发布的WMS图层建立缓存切片。

服务发布步骤：

1）官网下载 geowebcache-1.8.0-war.zip，直接解压得到geowebcache.war文件，将该文件直接拷贝至tomcat目录下的webapps下即可，启动tomcat会对war包进行解压。

2）修改geowebcache的配置文件geowebcache-core-context.xml。该文件在Tomcat的webapps\geowebcache\WEB-INF下，修改如下：

<bean id="gwcXmlConfig" class="org.geowebcache.config.XMLConfiguration">

<constructor-arg ref="gwcAppCtx" />

<!--<constructor-arg ref="gwcDefaultStorageFinder" />-->

    <constructor-arg value="D:\\GisMap\\" />

<!-- By default GWC will look for geowebcache.xml in {GEOWEBCACHE_CACHE_DIR},

         if not found will look at GEOSEVER_DATA_DIR/gwc/

         alternatively you can specify an absolute or relative path to a directory

         by replacing the gwcDefaultStorageFinder constructor argument above by the directory

         path, like constructor-arg value="/etc/geowebcache"

    -->

<property name="template" value="/geowebcache.xml">

<description>Set the location of the template configuration file to copy over to the

        cache directory if one doesn't already exist.

</description>

</property>

</bean>

修改gwcXmlConfig实例化时使用固定路径，该路径可以为任意新建路径文件夹。Geowebcache启动之后会检查此文件夹下是否存在gewebcache.xml文件，如果不存在则按模板新建立并读取使用，如果存在则直接读取使用。

3）修改第2步中的gewebcache.xml文件：

<layers>

    <arcgisLayer>

        <name>ARCGIS-Demo</name>

        <tilingScheme>D:\\GisMap\\Layer\\conf.xml</tilingScheme>

        <tileCachePath>D:\\GisMap\\Layer\\_alllayers</tileCachePath>

    </arcgisLayer>

</layers>

在layers节点里添加arcgisLayer节点（默认生成的gewebcache.xml的layers节点有许多其他冗余数据，可删除可保留）。Name节点表示待添加图层的名称（这里配置为ARCGIS-Demo），titlingscheme节点为conf.xml文件的路径，tileCachePath为瓦片数据的路径。

4）瓦片地图的准备

其中conf.xml为配置文件，conf.cdi为显示区域约束文件，_alllayers文件夹下则存放了切片数据，Status.gdb为切片状态情况记录（可直接删除）。

通过瓦片下载器下载瓦片地图，然后生成的切片数据_alllayers文件夹：

L01-L10表示地图缩放级数，按照ArcGIS切片目录组织，切片命名规则也和ArcGIS切片数据命名规则一致。（conf.xml、conf.cdi和_alllayers在同级目录）。

5)启动tomcat，继而启动Geowebcache服务，浏览器访问 localhost:8080/geowebcache，如果一切正确的话可以看到下面的页面

该页面简单说明了Geowebcache的一些情况。

点击“A list of all the layers and automatic demos”连接可以看到下面：

该页面显示了geowebcache.xml配置的图层信息。图中可以看到只配置了一个名字为ARCGIS-Demo的图层，使用的EPSG3857坐标系，发布的图片格式为png格式，点击png链接即可看到瓦片地图。

这里地图显示的级别和坐标系配置都来自conf.xml文件。这里的前端js使用的是Openlayers。查看网页源码：

<html xmlns="http://www.w3.org/1999/xhtml"><head>

<meta http-equiv="imagetoolbar" content="no">

<title>ARCGIS-Demo EPSG:3857_ARCGIS-Demo image/png</title>

<style type="text/css">

body { font-family: sans-serif; font-weight: bold; font-size: .8em; }

body { border: 0px; margin: 0px; padding: 0px; }

#map { width: 85%; height: 85%; border: 0px; padding: 0px; }

</style>

<script src="../openlayers/OpenLayers.js"></script>

<script type="text/javascript">

var map, demolayer;

  // sets the chosen modifiable parameter

  function setParam(name, value){

   str = "demolayer.mergeNewParams({" + name + ": '" + value + "'})"

   // alert(str);

   eval(str);

  }

OpenLayers.DOTS_PER_INCH = 96.0;

OpenLayers.Util.onImageLoadErrorColor = 'transparent';

function init(){

var mapOptions = {

resolutions: [156543.033928, 78271.5169639999, 39135.7584820001, 19567.8792409999, 9783.93962049996, 4891.96981024998, 2445.98490512499, 1222.99245256249, 611.49622628138, 305.748113140558, 152.874056570411, 76.4370282850732, 38.2185141425366, 19.1092570712683, 9.55462853563415, 4.77731426794937, 2.38865713397468, 1.19432856685505, 0.597164283559817, 0.298582141647617],

projection: new OpenLayers.Projection('EPSG:3857'),

maxExtent: new OpenLayers.Bounds(-20037508.342787,-20037508.342780996,20037508.342780996,20037508.342787),

units: "meters",

controls: []

};

map = new OpenLayers.Map('map', mapOptions );

map.addControl(new OpenLayers.Control.PanZoomBar({

        position: new OpenLayers.Pixel(2, 15)

}));

map.addControl(new OpenLayers.Control.Navigation());

map.addControl(new OpenLayers.Control.Scale($('scale')));

map.addControl(new OpenLayers.Control.MousePosition({element: $('location')}));

demolayer = new OpenLayers.Layer.WMS(

"ARCGIS-Demo","../service/wms",

{layers: 'ARCGIS-Demo', format: 'image/png' },

{ tileSize: new OpenLayers.Size(256,256),

 tileOrigin: new OpenLayers.LonLat(-2.0037508342787E7, 2.0037508342787E7)});

map.addLayer(demolayer);

map.zoomToExtent(new OpenLayers.Bounds(-20037497.2108,-19929239.113399997,20037497.2108,18379686.9965));

// The following is just for GetFeatureInfo, which is not cached. Most people do not need this

map.events.register('click', map, function (e) {

  document.getElementById('nodelist').innerHTML = "Loading... please wait...";

  var params = {

    REQUEST: "GetFeatureInfo",

    EXCEPTIONS: "application/vnd.ogc.se_xml",

    BBOX: map.getExtent().toBBOX(),

    X: e.xy.x,

    Y: e.xy.y,

    INFO_FORMAT: 'text/html',

    QUERY_LAYERS: map.layers[0].params.LAYERS,

    FEATURE_COUNT: 50,

    Layers: 'ARCGIS-Demo',

    Styles: '',

    Srs: 'EPSG:3857',

    WIDTH: map.size.w,

    HEIGHT: map.size.h,

    format: "image/png" };

  OpenLayers.loadURL("../service/wms", params, this, setHTML, setHTML);

  OpenLayers.Event.stop(e);

  });

}

function setHTML(response){

    document.getElementById('nodelist').innerHTML = response.responseText;

};

</script>

</head>

<body onload="init()">

<div id="params"></div>

<div id="map"></div>

<div id="nodelist"></div>

</body>

</html>

个人比较喜欢leaflet这个GIS javascript库，使用leaflet加载GeoWebCache发布的这个服务：

<!DOCTYPE html>

<html>

<head>

    <title>Leaflet - Offline Demo</title>

    <link rel="stylesheet" href="https://unpkg.com/leaflet@1.0.3/dist/leaflet.css" />

    <script src="https://unpkg.com/leaflet@1.0.3/dist/leaflet.js"></script>

</head>

<body>

    <div id="map" style="height:100vh;" ></div>

    <script type="text/javascript">

    var mapCenter = new L.LatLng(32.1280, 118.7742); //南京

    var map = new L.Map('map', {

        center : mapCenter,

        zoom : 4

    });

    var wmsLayer = L.tileLayer.wms("http://localhost:8080/geowebcache/service/wms", {

        layers: 'ARCGIS-Demo',

        format: 'image/png'

    });

    wmsLayer.addTo(map);

    var marker = new L.Marker(mapCenter);

    map.addLayer(marker);

    marker.bindPopup("<p>Hello! ;}</p>").openPopup();

    </script>

</body>

</html>

3、使用自定义的Http服务

GeowebCache本质上就是个Http服务，通过请求参数获取配置文件中的路径中的切片数据，返回给请求方。

我们可以自己写个独立的Http服务，从数据库中读取切片数据返回给请求方。

切片请求地址类似：http://localhost:8899/1818940751/{z}/{x}/{y}

其中“1818940751”是下载器下载的地图类型，z/x/y分别是zoom和地图切片行列号。

前端js使用leaflet加载：

var amapNormalUrl = 'http://localhost:8899/788865972/{z}/{x}/{y}';

var amapNormalLayer = new L.TileLayer(amapNormalUrl, {

    minZoom : 1,

    maxZoom : 18,

    attribution : '高德普通地图'

});

var mapCenter = new L.LatLng(32.1280, 118.7742); //南京

var map = new L.Map('map', {

        center : mapCenter,

        zoom : 9,

        minZoom: 1,

        maxZoom: 18,

        layers : [ amapNormalLayer ]

});

前端js可以自定义投影Projection算法，而国内google地图、高德地图和腾讯地图都是标准的墨卡托投影，可以直接用leaflet加载。

配合一些画图插件，再配合一些后台POI检索服务，如：

《使用Lucene索引和检索POI数据》

《使用Solr进行空间搜索》

则能做出如下效果：

总结：介绍了如何使用下载的离线切片数据在局域网环境下发布Web GIS地图服务，前端配合使用一些js插件，实现web下空间数据的检索。

在Github上开源了一些代码，包含自定义的Http地图服务，和一个简单的页面WebGISDemo。

地址：

https://github.com/luxiaoxun/MapDownloader

https://github.com/luxiaoxun/Code4Java

附件：

<?xml version="1.0" encoding="utf-8" ?>

<EnvelopeN xsi:type='typens:EnvelopeN'

    xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'

    xmlns:xs='http://www.w3.org/2001/XMLSchema'

    xmlns:typens='http://www.esri.com/schemas/ArcGIS/10.1'>

    <XMin>-20037497.2108</XMin>

    <YMin>-19929239.113399997</YMin>

    <XMax>20037497.2108</XMax>

    <YMax>18379686.9965</YMax>

</EnvelopeN>

conf.cdi

<?xml version="1.0" encoding="utf-8"?>

<CacheInfo xsi:type="typens:CacheInfo" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:typens="http://www.esri.com/schemas/ArcGIS/10.1">

    <TileCacheInfo xsi:type="typens:TileCacheInfo">

        <SpatialReference xsi:type="typens:ProjectedCoordinateSystem">

            <WKT>PROJCS["WGS_1984_Web_Mercator_Auxiliary_Sphere",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Mercator_Auxiliary_Sphere"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",0.0],PARAMETER["Standard_Parallel_1",0.0],PARAMETER["Auxiliary_Sphere_Type",0.0],UNIT["Meter",1.0],AUTHORITY["EPSG",3857]]</WKT>

            <XOrigin>-20037700</XOrigin>

            <YOrigin>-30241100</YOrigin>

            <XYScale>148923141.92838538</XYScale>

            <ZOrigin>-100000</ZOrigin>

            <ZScale>10000</ZScale>

            <MOrigin>-100000</MOrigin>

            <MScale>10000</MScale>

            <XYTolerance>0.001</XYTolerance>

            <ZTolerance>0.001</ZTolerance>

            <MTolerance>0.001</MTolerance>

            <HighPrecision>true</HighPrecision>

            <WKID>3857</WKID>

        </SpatialReference>

        <TileOrigin xsi:type="typens:PointN">

            <X>-20037508.342787001</X>

            <Y>20037508.342787001</Y>

        </TileOrigin>

        <TileCols>256</TileCols>

        <TileRows>256</TileRows>

        <DPI>96</DPI>

        <LODInfos xsi:type="typens:ArrayOfLODInfo">

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>0</LevelID>

                <Scale>591657527.591555</Scale>

                <Resolution>156543.03392799999</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>1</LevelID>

                <Scale>295828763.79577702</Scale>

                <Resolution>78271.516963999893</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>2</LevelID>

                <Scale>147914381.89788899</Scale>

                <Resolution>39135.758482000099</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>3</LevelID>

                <Scale>73957190.948944002</Scale>

                <Resolution>19567.879240999901</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>4</LevelID>

                <Scale>36978595.474472001</Scale>

                <Resolution>9783.9396204999593</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>5</LevelID>

                <Scale>18489297.737236001</Scale>

                <Resolution>4891.9698102499797</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>6</LevelID>

                <Scale>9244648.8686180003</Scale>

                <Resolution>2445.9849051249898</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>7</LevelID>

                <Scale>4622324.4343090001</Scale>

                <Resolution>1222.9924525624899</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>8</LevelID>

                <Scale>2311162.2171550002</Scale>

                <Resolution>611.49622628138002</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>9</LevelID>

                <Scale>1155581.108577</Scale>

                <Resolution>305.74811314055802</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>10</LevelID>

                <Scale>577790.55428899999</Scale>

                <Resolution>152.874056570411</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>11</LevelID>

                <Scale>288895.27714399999</Scale>

                <Resolution>76.437028285073197</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>12</LevelID>

                <Scale>144447.638572</Scale>

                <Resolution>38.218514142536598</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>13</LevelID>

                <Scale>72223.819285999998</Scale>

                <Resolution>19.109257071268299</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>14</LevelID>

                <Scale>36111.909642999999</Scale>

                <Resolution>9.5546285356341496</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>15</LevelID>

                <Scale>18055.954822</Scale>

                <Resolution>4.7773142679493699</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>16</LevelID>

                <Scale>9027.9774109999998</Scale>

                <Resolution>2.38865713397468</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>17</LevelID>

                <Scale>4513.9887049999998</Scale>

                <Resolution>1.1943285668550501</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>18</LevelID>

                <Scale>2256.994353</Scale>

                <Resolution>0.59716428355981699</Resolution>

            </LODInfo>

            <LODInfo xsi:type="typens:LODInfo">

                <LevelID>19</LevelID>

                <Scale>1128.4971760000001</Scale>

                <Resolution>0.29858214164761698</Resolution>

            </LODInfo>

        </LODInfos>

    </TileCacheInfo>

    <TileImageInfo xsi:type="typens:TileImageInfo">

        <CacheTileFormat>PNG</CacheTileFormat>

        <CompressionQuality>0</CompressionQuality>

        <Antialiasing>false</Antialiasing>

    </TileImageInfo>

    <CacheStorageInfo xsi:type="typens:CacheStorageInfo">

        <StorageFormat>esriMapCacheStorageModeExploded</StorageFormat>

        <PacketSize>0</PacketSize>

    </CacheStorageInfo>

</CacheInfo>

conf.xml

参考：

http://leafletjs.com/

http://leafletjs.com/examples/quick-start/

http://www.cnblogs.com/luxiaoxun/p/4454880.html

http://www.cnblogs.com/luxiaoxun/p/5020247.html

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