空间数据格式(地理数据格式)：GeoJSON(FeatureCollection)与EsriJSON(FeatureSet/ArcGIS格式)

一、FeatureCollection(GeoJSON)格式介绍

https://learn.microsoft.com/en-us/javascript/api/azure-maps-control/atlas.data.featurecollection?view=azure-maps-typescript-latest

1、FeatureCollection格式

{
  type: "FeatureCollection",
  features: [{
    type: "Feature",
    geometry: geometry,
    properties: {}
  }]
}

 2、 Geometry格式

{
    type: "Point | MultiPoint | LineString | MultiLineString | Polygon | MultiPolygon",
    coordinates: 数组
}

3、Point数组 ，也是下文的position数组

[longitude, latitude, elevation].
position: [longitude, latitude, elevation]

4、MultiPoint数组

coordinates:position[]

5、LineString数组

coordinates:position[]

6、MultiLineString数组

coordinates:position[][]

7、Polygon数组

coordinates:Position[][]

8、MultiPolygon数组　

coordinates:position[][][]

二、FeatureSet，EsriJSON格式介绍

1、FeatureSet格式

{
	"objectIdFieldName": "objectid",
	"globalIdFieldName": "globalid",
	"geometryType": "esriGeometryPoint | esriGeometryMultipoint | esriGeometryPolyline | esriGeometryPolygon | esriGeometryEnvelope",
	"spatialReference": {
		"wkid": 102100,
		"latestWkid": 3857
	},
	"fields": [{
		"name": "objectid",
		"alias": "OBJECTID",
		"type": "esriFieldTypeOID"
	}],
	"features": [{
		"geometry": {},
		"attributes": {}
	}]
}

2、Point类型的geometry

A 2D point
geometry:{
  "x": -118.15,
  "y": 33.80,
  "spatialReference": {
    "wkid": 4326
  }
} 

3、MultiPoint类型的Geometry

A 2D multipoint
geometry:{
  "points": [
    [
      -97.06138,
      32.837
    ],
    [
      -97.06133,
      32.836
    ] 
  ],
  "spatialReference": {
    "wkid": 4326
  }
}

4、Polyline类型的Geometry

2D polylines
geometry:{
  "paths": [
    [
      [-97.06138,32.837],
      [-97.06133,32.836],
      [-97.06124,32.834],
      [-97.06127,32.832]
    ], 
    [
      [-97.06326,32.759],
      [-97.06298,32.755]
    ]
  ],
  "spatialReference": {"wkid": 4326}
}

5、PolyGon类型的Geometry

A 2D polygon
geometry:{
  "rings": [
    [
      [-97.06138,32.837],
      [-97.06133,32.836],
      [-97.06124,32.834],
      [-97.06127,32.832],
      [-97.06138,32.837]
    ],
    [
      [-97.06326,32.759],
      [-97.06298,32.755],
      [-97.06153,32.749],
      [-97.06326,32.759]
    ]
  ],
  "spatialReference": {
    "wkid": 4326
  }
}　　

三、GeoJSON和EsriJSON的异同点

1、属性信息的异同点

geojson没有关于属性元数据的描述，fields数组、displayfield字段等；相同点是都在feature内部记录，geojson的属性字段为properties,esrijson的属性字段为attruibutes

2、坐标信息的异同点

geojson的坐标信息由不同维度的数组表示，由coordinates属性表示，每个geometry用type属性来区分是什么类型的几何；esrijson的单点是用x/y属性记录，其余多点、线、面用二维和三维数组记录，区分不同类型的几何体取决于geometry对象内的属性字段，分别为points,paths,rings。esrijson没有multipolygon和multipolyline。相同点是，二者多点和面的数组维度是一致的。