如何使用 Observable 和 turf.js 构建多边形？

Question

我正在使用来自数据库的坐标构建多边形。我已经订阅了一个 Observable 来获取所有坐标（这是一个数组）。我将每个坐标数组推送到上数组中，以便能够构建我的多边形：

this.customerApi.getLocations(this.currentUser.id)
    .subscribe((response) => {
      this.locations = response;
      this.polygonsArray.push(this.locations);
      this.locations.forEach(element 
      => {this.polygons.push(element.geoDefinition.features['0'].geometry.coordinates);
       });

getLocations returns 3 个数组：

然后我将这些数组推送到一个名为 this.polygons:

的上层数组中

我的问题是当我打电话给 const varpolygon = turf.polygon(this.polygons);

我收到以下错误：

 Uncaught (in promise): Error: Each LinearRing of a Polygon must have 4 or more Positions.
Error: Each LinearRing of a Polygon must have 4 or more Positions.

我认为我的数组结构很好，因为多边形是一个由坐标数组组成的数组。类型是 number[][][]，比如 turf.polygon.

我的 validated GEOJSON 的结构是：

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [
              5.379856000000018,
              43.252967
            ],
            [
              5.422988000000032,
              43.249466
            ],
            [
              5.425048000000061,
              43.245153
            ],
            [
              5.383804000000055,
              43.239838
            ],
            [
              5.399856,
              43.212967
            ],
            [
              5.379856000000018,
              43.252967
            ]
          ]
        ]
      },
      "properties": {}
    },
    {
      "type": "Feature",
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [
              5.390139999999974,
              43.279295
            ],
            [
              5.393068999999969,
              43.279249
            ],
            [
              5.391814000000068,
              43.278421
            ],
            [
              5.390709000000015,
              43.278749
            ],
            [
              5.390899999999988,
              43.2785
            ],
            [
              5.390139999999974,
              43.279295
            ]
          ]
        ]
      },
      "properties": {}
    },
    {
      "type": "Feature",
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [
              -0.6070509999999558,
              44.840753
            ],
            [
              -0.5437080000000378,
              44.832962
            ],
            [
              -0.5222499999999854,
              44.820544
            ],
            [
              -0.5663670000000138,
              44.808853
            ],
            [
              -0.5863669999999956,
              44.788853
            ],
            [
              -0.6070509999999558,
              44.840753
            ]
          ]
        ]
      },
      "properties": {}
    }
  ]
}

如果是这种情况，有人可以告诉我我做错了什么并帮助我吗？

在此先感谢您的帮助。

Answer 1

this.polygons 是一个多边形数组，因此它不是一个单一的多边形

for(var i;i<this.polygons.length;i++){
    polygon = turf.polygon(this.polygons[i]);
}

通过这种方式，您可以为每个不同的多边形创建单独的草皮多边形。

或者，如果您想创建一个草皮多边形，您需要做的是创建一个草皮多多边形

var turfpolygon = turf.multiPolygon(this.polygons);

如何使用 Observable 和 turf.js 构建多边形？

How to build polygons with Observable and turf.js?

geojson

typescript

turfjs