measurement

along

npm install @turf/along

接收入参的线段上指定距离的点。

值得注意的是，距离是从起点开始计算的，如果距离超过线段的长度，会返回终点的 GeoJSON

参数

options

返回

Feature<Point>

范例

var line = turf.lineString([
  [-83, 30],
  [-84, 36],
  [-78, 41]
]);
var options = { units: "miles" };
var along = turf.along(line, 200, options);
/*
{
  type: "Feature",
  geometry: {
    coordinates: [-83.4608648621918, 32.8678095806294],
    type: "Point"
  },
  properties: {}
}
*/

area

npm install @turf/area

接收入参的要素(Feature)或要素集(FeatureCollection)，计算并返回它们的面积

值得注意的是，该方法应该是传入 polygon 类型的 GeoJSON，即 Point 点类型和 LineString 线段类型均为 0

参数

返回

Number - 面积大小

范例

var polygon = turf.polygon([
  [
    [125, -15],
    [113, -22],
    [154, -27],
    [144, -15],
    [125, -15]
  ]
]);
var area = turf.area(polygon); // 3339946239196.927
// 多要素
var area = turf.area({
  type: "FeatureCollection",
  features: [
    turf.polygon([
      [
        [125, -15],
        [113, -22],
        [154, -27],
        [144, -15],
        [125, -15]
      ]
    ]),
    turf.polygon([
      [
        [225, -15],
        [213, -22],
        [254, -27],
        [244, -15],
        [225, -15]
      ]
    ])
  ]
}); // 6679892478393.854

bbox

npm install @turf/bbox

接收入参要素，返回它的边界框(bbox)

边界框是由右上角的坐标和左下角的坐标组成的一位数组

参数

返回

BBox - 以 minX、minY、maxX、maxY 的顺序排列

范例

var line = turf.lineString([
  [-74, 40],
  [-78, 42],
  [-82, 35]
]);
var bbox = turf.bbox(line); // [-82, 35, -74, 42]
var bboxPolygon = turf.bboxPolygon(bbox);

bboxPolygon

npm install @turf/bbox-polygon

接收一个入参 bbox(边界框)，返回它的的等效 GeoJSON

参数

options

返回

Feature<Polygon>

范例

var bbox = [0, 0, 10, 10];
var poly = turf.bboxPolygon(bbox);
/*
{
  type: "Feature",
  geometry: {
    type: "Polygon",
    coordinates: [
      [0, 0], [10, 0], [10, 10], [0, 10], [0, 0]
    ]
  },
  properties: {}
}
*/

bearing

npm install @turf/bearing

接收两个点类型的 GeoJSON，计算获取二者之间的地理方位，并与正北方向所形成的角度

即以起始点为参照物，终止点的偏移角度

参数

options

返回

Number - 返回的数值介于 -180 至 180 之间，顺时针为正值

范例

var point1 = turf.point([-75.343, 39.984]);
var point2 = turf.point([-75.534, 39.123]);
var bearing = turf.bearing(point1, point2); // -170.2330491349224
var bearing = turf.bearing(point1, point2, { final: true }); // 189.6453188611693
// 也可以用经纬度坐标
var bearing = turf.bearing([-75.343, 39.984], [-75.534, 39.123]); // -170.2330491349224

center

npm install @turf/center

接收入参要素(Feature)或要素集(FeatureCollection)，计算并返回它们的绝对中心点

参数

options

返回

Feature<Point> - 绝对中心

范例

var features = turf.featureCollection([
  turf.point([-97.522259, 35.4691]),
  turf.point([-97.502754, 35.463455]),
  turf.point([-97.508269, 35.463245])
]);
var center = turf.center(features);
/*
{
  type: "Feature",
  geometry: {
    coordinates: [-97.5125065, 35.4661725],
    type: "point"
  },
  properties: {}
}
*/
// 单一要素
var center = turf.center(
  turf.polygon([
    [
      [-97.522259, 35.4691],
      [-97.502754, 35.463455],
      [-97.508269, 35.463245],
      [-97.522259, 35.4691]
    ]
  ]),
  {
    properties: {
      desc: "center point"
    }
  }
);
/*
{
  type: "Feature",
  geometry: {
    coordinates: [-97.5125065, 35.4661725],
    type: "point"
  },
  properties: {
    desc: "center point"
  }
}
*/

centerOfMass

npm install @turf/center-of-mass

接收入参要素(Feature)或要素集(FeatureCollection)，计算并返回它们的质心

参数

返回

Feature<Point> - 质心

范例

var polygon = turf.polygon([
  [
    [-81, 41],
    [-88, 36],
    [-84, 31],
    [-80, 33],
    [-77, 39],
    [-81, 41]
  ]
]);
var center = turf.centerOfMass(polygon, {
  desc: "center of mass"
});
/*
{
  type: "Feature",
  geometry: {
    type: "Point",
    coordinates: [-82.3109243697479, 36.134453781512605]
  },
  properties: {
    desc: "center of mass"
  }
}
*/

centroid

npm install @turf/centroid

接收入参要素(Feature)或要素集(FeatureCollection)，计算并返回它们的矩心

参数

返回

Feature<Point> - 矩心

范例

var polygon = turf.polygon([
  [
    [-81, 41],
    [-88, 36],
    [-84, 31],
    [-80, 33],
    [-77, 39],
    [-81, 41]
  ]
]);
var centroid = turf.centroid(polygon, {
  desc: "centroid"
});
/*
{
  type: "Feature",
  geometry: {
    type: "Point",
    coordinates: [-82, 36]
  },
  properties: {
    desc: "centroid"
  }
}
*/

destination

npm install @turf/destination

接收入参的点作为参照物，通过指定单位的距离计算出目标点的位置

若以 degress 为单位，将使用 Haversine 公式说明整体曲率

参数

options

返回

Feature<Point> - 目标点

范例

var point = turf.point([-75.343, 39.984]);
var distance = 50;
var bearing = 90;
var options = { units: "miles" };
var destination = turf.destination(point, distance, bearing, options);
/*
{
  type: "Feature",
  geometry: {
    type: "Point",
    coordinates: [-74.39858826442095, 39.98016766669771]
  },
  properties: {}
}
*/

distance

npm install @turf/distance

计算两点之间的距离

若以 degress 为单位，将使用 Haversine 公式说明整体曲率

参数

options

返回

Number - 两点的距离

范例

var from = turf.point([-75.343, 39.984]);
var to = turf.point([-75.534, 39.123]);
var options = { units: "miles" };
var distance = turf.distance(from, to, options); // 60.35329997171415

envelope

npm install @turf/envelope

接收任意要素(Feature)或要素集(FeatureCollection)，返回包含所有顶点的 type 为 Polygon 的矩形 GeoJSON

值得注意的是，矩形是正四边形，所以会去包含更靠外的要素顶点，从而保证所有的要素都在矩形内

参数

返回

Feature<Polygon> - 包含所有入参要素顶点的 GeoJSON

范例

var features = turf.featureCollection([
  turf.point([-75.343, 39.984], { name: "Location A" }),
  turf.point([-75.833, 39.284], { name: "Location B" }),
  turf.point([-75.534, 39.123], { name: "Location C" })
]);
var enveloped = turf.envelope(features);
/*
{
  type: "Feature",
  geometry: {
    type: "Polygon",
    coordinates: [
      [
        [-75.833, 39.123],
        [-75.343, 39.123],
        [-75.343, 39.984],
        [-75.833, 39.984],
        [-75.833, 39.123]
      ]
    ]
  },
  properties: {}
}
*/
// 包含更靠外的要素，第四个点[-75.12, 38.4]比第三个点[-75.534, 39.123]有更小的维度，所以第三个点不在矩形的边上
var features = turf.featureCollection([
  turf.point([-75.343, 39.984], { name: "Location A" }),
  turf.point([-75.833, 39.284], { name: "Location B" }),
  turf.point([-75.534, 39.123], { name: "Location C" }),
  turf.point([-75.12, 38.4], { name: "Location D" })
]);
var enveloped = turf.envelope(features);

length

npm install @turf/length

接收入参 GeoJSON 的长度，通过特定的单位计算长度

type 为(Multi)Point 的 GeoJSON 长度为 0

参数

options

返回

Number - 长度

范例

var line = turf.lineString([
  [115, -32],
  [131, -22],
  [143, -25],
  [150, -34]
]);
var length = turf.length(line, { units: "miles" }); // 2738.9663893575207

midpoint

npm install @turf/midpoint

接收两个点，通过地球的曲率计算出中点，并返回该中点

参数

返回

Feature<Point>

范例

var point1 = turf.point([144.834823, -37.771257]);
var point2 = turf.point([145.14244, -37.830937]);
var midpoint = turf.midpoint(point1, point2);
/*
{
  type: "Feature",
  geometry: {
    type: "Point",
    coordinates: [144.98856936202512, -37.801196981553204]
  },
  properties: {}
}
*/

pointOnFeature

npm install @turf/point-on-feature

接收入参的要素(Feature)或要素集(FeatureCollection)，返回一个保证在要素表面的 type 为 Point 的 GeoJSON

值得注意的是，返回的点要素是固定的，并非随机

参数

返回

Feature<Point>

范例

var polygon = turf.polygon([
  [
    [116, -36],
    [131, -32],
    [146, -43],
    [155, -25],
    [133, -9],
    [111, -22],
    [116, -36]
  ]
]);
var pointOnPolygon = turf.pointOnFeature(polygon);
/*
{
  type: "Feature",
  geometry: {
    type: "Point",
    coordinates: [133, -26]
  },
  properties: {}
}
*/

polygonTangents

npm install @turf/polygon-tangents

接收一个点和一个(Multi)Polygon，计算二者的切线，返回切线在(Multi)Polygon 上的点

参数

返回

Feature<Point> - 包含两个切点的要素集合

范例

var polygon = turf.polygon([
  [
    [11, 0],
    [22, 4],
    [31, 0],
    [31, 11],
    [21, 15],
    [11, 11],
    [11, 0]
  ]
]);
var point = turf.point([61, 5]);
var tangents = turf.polygonTangents(point, polygon);
/*
{
  type: "FeatureCollection",
  features: [
    {
      type: "Feature",
      geometry: {
        type: "point",
        coordinates: [21, 15]
      },
      properties: {}
    },
    {
      type: "Feature",
      geometry: {
        type: "point",
        coordinates: [31, 0]
      },
      properties: {}
    }
  ]
}
*/

pointToLineDistance

npm install @turf/point-to-line-distance

接收一个点和一条线段，获取二者之间的最小距离

参数

options

返回

Number - 距离

范例

var pt = turf.point([0, 0]);
var line = turf.lineString([
  [1, 1],
  [-1, 1]
]);
var distance = turf.pointToLineDistance(pt, line, { units: "miles" }); // 69.11854715938406

rhumbBearing

npm install @turf/rhumb-bearing

接收两个点，获取二者沿 Rhumb line 与正北方向所形成的角度

什么是rhumb line

参数

options

返回

Number - 返回的数值介于 -180 至 180 之间，顺时针为正值

范例

var point1 = turf.point([-75.343, 39.984], { "marker-color": "#F00" });
var point2 = turf.point([-75.534, 39.123], { "marker-color": "#00F" });
var bearing = turf.rhumbBearing(point1, point2); // -170.29417535572546
var bearing = turf.rhumbBearing(point1, point2, { final: true }); // 9.705824644274514

rhumbDestination

npm install @turf/rhumb-destination

获取以入参的点为参照物，通过指定单位的距离计算出沿 rhumb line 的目标点的位置

什么是rhumb line

参数

options

返回

Number - 目标点

范例

var pt = turf.point([-75.343, 39.984], { "marker-color": "F00" });
var distance = 50;
var bearing = 90;
var options = { units: "miles" };
var destination = turf.rhumbDestination(pt, distance, bearing, options);
/*
{
  type: "Feature",
  geometry: {
    type: "Point",
    coordinates: [-74.3985529486182, 39.984]
  },
  properties: {}
}
*/

rhumbDistance

npm install @turf/rhumb-distance

接收两个点，计算二者沿 rhumb line 的距离

什么是rhumb line

参数

options

返回

Number - 距离

范例

var from = turf.point([-75.343, 39.984]);
var to = turf.point([-75.534, 39.123]);
var options = { units: "miles" };
var distance = turf.rhumbDistance(from, to, options); // 60.35331130430885

square

npm install @turf/square

接收 bbox(边界框) 计算包含入参的最小正方形边界

参数

返回

BBox

范例

var bbox = [-20, -20, -15, 0];
var squared = turf.square(bbox); // [-27.5, -20, -7.5, 0]

greatCircle

npm install @turf/great-circle

接收两个点，计算二者的大圆路线，返回 type 为 LineString 的大圆线 GeoJSON

参数

options

返回

Feature<LineString> - 大圆线

范例

var start = turf.point([-122, 48]);
var end = turf.point([-77, 39]);
var greatCircle = turf.greatCircle(start, end, { name: "Seattle to DC" });