arcgis for js 3使用4490坐标系加载天地图

喜欢ヅ旅行 2022-11-18 15:59 842阅读 0赞

我以往使用arcgis for js 3.19加载天地图，使用的都是默认的坐标系：4326。现在因为客户提供的地图，都是4490的，没办法，只能全部使用4490，否则不同坐标系的图层，没办法叠在一起。

4490是CGCS2000坐标系的WKID，4326是WGS84的WKID。有关它们的区别与联系，请阅读尾部的参考文章。有说法称，4490比4326更适合我们多一些。

以下是加载天地图的完整代码，写成了arcgis插件的形式：

define(["dojo/_base/declare","esri/layers/tiled"],function(declare) { 
    	return declare(esri.layers.TiledMapServiceLayer, { 
    		constructor: function(path, option) { 
    			this.baseUrl = path;
    			this.layerType = option ? option.mode : null;
    			if(option.name){ 
    				this.id = option.name;
    			}
    			this.tk = getTk(option);
    			this.spatialReference = new esri.SpatialReference({ 
    				wkid: 4490
    			});
    			this.initialExtent = (this.fullExtent = new esri.geometry.Extent(45.0, -27.0, 163.0,45.0,
    				this.spatialReference));//中国及周边范围
    			this.tileInfo = getTileInfo();
    			this.loaded = true;
    			this.onLoad(this);
    			
    			function getTk(option){ 
    				var tk;
    				
    				if(option.tk){ 
    					tk = option.tk;
    				} else { 
    					console.error("欠缺天地图的TK！！！");
    				}
    				
    				return tk;
    			}
    			function getTileInfo(){ 
    				return new esri.layers.TileInfo({ 
    					/* titleInfo可从图层中获取 */
    					"dpi": 96,
    					"rows": 256,
    					"cols": 256,
    					"compressionQuality": 0,
    					"origin": { 
    						x: -180,
    						y: 90
    					},
    					"spatialReference": { 
    						"wkid": 4490,
    						"latestWkid": 4490
    					},
    					/* scale:比例尺 ，resolution:分辨率 */    
    					"lods": [ 
    						{  level: 0, resolution: 1.40625, scale: 590995197.14166909755553014475 },
    						{ 
    							"level": 1,
    							"resolution": 0.7031250000000002,
    							"scale": 2.9549759305875003E8
    						},
    						{ 
    							"level": 2,
    							"resolution": 0.3515625000000001,
    							"scale": 1.4774879652937502E8
    						},
    						{ 
    							"level": 3,
    							"resolution": 0.17578125000000006,
    							"scale": 7.387439826468751E7
    						},
    						{ 
    							"level": 4,
    							"resolution": 0.08789062500000003,
    							"scale": 3.6937199132343754E7
    						},
    						{ 
    							"level": 5,
    							"resolution": 0.043945312500000014,
    							"scale": 1.8468599566171877E7
    						},
    						{ 
    							"level": 6,
    							"resolution": 0.021972656250000007,
    							"scale": 9234299.783085939
    						},
    						{ 
    							"level": 7,
    							"resolution": 0.010986328125000003,
    							"scale": 4617149.891542969
    						},
    						{ 
    							"level": 8,
    							"resolution": 0.005493164062500002,
    							"scale": 2308574.9457714846
    						},
    						{ 
    							"level": 9,
    							"resolution": 0.002746582031250001,
    							"scale": 1154287.4728857423
    						},
    						{ 
    							"level": 10,
    							"resolution": 0.0013732910156250004,
    							"scale": 577143.7364428712
    						},
    						{ 
    							"level": 11,
    							"resolution": 6.866455078125002E-4,
    							"scale": 288571.8682214356
    						},
    						{ 
    							"level": 12,
    							"resolution": 3.433227539062501E-4,
    							"scale": 144285.9341107178
    						},
    						{ 
    							"level": 13,
    							"resolution": 1.7166137695312505E-4,
    							"scale": 72142.9670553589
    						},
    						{ 
    							"level": 14,
    							"resolution": 8.583068847656253E-5,
    							"scale": 36071.48352767945
    						},
    						{ 
    							"level": 15,
    							"resolution": 4.2915344238281264E-5,
    							"scale": 18035.741763839724
    						},
    						{ 
    							"level": 16,
    							"resolution": 2.1457672119140632E-5,
    							"scale": 9017.870881919862
    						},
    						{ 
    							"level": 17,
    							"resolution": 1.0728836059570316E-5,
    							"scale": 4508.935440959931
    						},
    						{ 
    							"level": 18,
    							"resolution": 5.364418029785158E-6,
    							"scale": 2254.4677204799655
    						}
    					]
    				});            
    			}
    		}, //end of constructor
    		baseUrl: null,
    		layerType: null,
    		tk: null,
    		id:null,
    		getTileUrl: function (level, row, col) { 
    			return this.baseUrl 
    				+ "?SERVICE=WMTS&REQUEST=GetTile&VERSION=1.0.0&STYLE=default&TILEMATRIXSET=c&FORMAT=tiles"
    				+ "&LAYER=" + this.layerType 
    				+ "&TILEMATRIX=" + level 
    				+ "&TILEROW=" + row 
    				+ "&TILECOL=" + col 
    				+ "&tk=" + this.tk;
    		}
    	});
    });

代码中，

"lods": [ 
    			{  level: 0, resolution: 1.40625, scale: 590995197.14166909755553014475 },
    			{ 
    				"level": 1,
    				"resolution": 0.7031250000000002,
    				"scale": 2.9549759305875003E8
    			},

这部分比较神秘。我也不能确定这是啥，但从许多4490图层的信息来看，这应该是一种类似地图切片的方案或比例尺之类。你看，以下是一幅4490坐标系的底图：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xlZnRmaXN0_size_16_color_FFFFFF_t_70_pic_center]  
里面的数字与代码中是一样的。不过它的Level 0对应了代码中的Level 1。只有代码中这样设置，天地图才能加载得出来。不清楚是什么原因。也许当前（2021年4月）版本的天地图就是这样子的。

参考文章  
[GIS开发扫盲贴–地理坐标系][GIS]

[wkid=4326, 4490,cgcs2000,坐标系总结（高德爬取的坐标叠加到84上是什么样）][wkid_4326_ 4490_cgcs2000_84]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xlZnRmaXN0_size_16_color_FFFFFF_t_70_pic_center]: /images/20221022/ac616bcc0dbe4e04a37c3584873fe126.png
[GIS]: https://blog.csdn.net/leftfist/article/details/106647860
[wkid_4326_ 4490_cgcs2000_84]: https://www.cnblogs.com/yansc/p/14212761.html