Question

我需要将（谷歌地图）边界对象转换为区域对象。

样本边界：

{
  northeast: {
    lat: 47.5085913,
    lng: 19.2656781
  },
  southwest: {
    lat: 47.4179006,
    lng: 19.0494985
  }
}

示例区域：

{
  // centre of bounds
  latitude,
  longitude,

  // delta of the centre in order to fit the original bounds
  latitudeDelta,
  longitudeDelta,
}

到目前为止我取得的成就：

const bounds2region = bounds => {
  const earthRadiusInKM = 6371 // km
  const radiusInKM = 1
  const aspectRatio = 1
  const [ latitude, longitude ] = bounds2center(bounds)
  const radiusInRad = radiusInKM / earthRadiusInKM
  const longitudeDelta = rad2deg(radiusInRad / Math.cos(deg2rad(latitude)))
  const latitudeDelta = aspectRatio * rad2deg(radiusInRad)

  return {
    latitude,
    longitude,
    latitudeDelta,
    longitudeDelta,
  }
}

const bounds2center = bounds =>
  toArrayIfObject(bounds)
    .reduce((coordinate1, coordinate2) => {
      const c1 = toArrayIfObject(coordinate1)
      const c2 = toArrayIfObject(coordinate2)

      return [
        average([c1[0], c2[0]]),
        average([c1[1], c2[1]]),
      ]
    })

const average = numbers => numbers.reduce((sum, n) => sum + n, 0) / numbers.length
const deg2rad = n => n * Math.PI / 180
const rad2deg = n => n / Math.PI * 180
const toArrayIfObject = object => typeof object === 'object' ? Object.values(object) : object

它部分工作：它将地图移动到边界的中心，但裁剪或缩小太多。我不确定如何设置增量（latitudeDelta，longitudeDelta）。我想我需要为aspectRatio计算一个值，而不是将其设置为1。

Answer 1

好的，经过一些冲浪后，我设法修补了一个解决方案：

fetch

函数const earthRadiusInMetre = 6371e3 const boundsToRegion = (bounds, aspectRatio = 1, margin = 1) => { const [ latitude, longitude ] = boundsToCenter(bounds) const R = (calculateDistance(bounds[0], { latitude, longitude })) * margin return { latitude, longitude, ...calculateRegionDelta({ latitude }, R, aspectRatio), } } const calculateRegionDelta = ({ latitude }, radiusInMetre, aspectRatio = 1) => { const radiusInRad = radiusInMetre / earthRadiusInMetre const longitudeDelta = rad2deg(radiusInRad / Math.cos(deg2rad(latitude))) const latitudeDelta = aspectRatio * rad2deg(radiusInRad) return { latitudeDelta, longitudeDelta, } } const boundsToCenter = bounds => bounds.reduce((coordinate1, coordinate2) => [ average([coordinate1.latitude, coordinate2.latitude]), average([coordinate1.longitude, coordinate2.longitude]), ]) const calculateDistance = (coord1, coord2) => { const R = earthRadiusInMetre const lat1 = coord1.latitude const lat2 = coord2.latitude const lon1 = coord1.longitude const lon2 = coord2.longitude const φ1 = deg2rad(lat1) const φ2 = deg2rad(lat2) const Δφ = deg2rad(lat2 - lat1) const Δλ = deg2rad(lon2 - lon1) const a = Math.sin(Δφ / 2) * Math.sin(Δφ / 2) + Math.cos(φ1) * Math.cos(φ2) * Math.sin(Δλ / 2) * Math.sin(Δλ / 2) const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a)) return R * c } const deg2rad = n => n * Math.PI / 180 const rad2deg = n => n / Math.PI * 180 const average = numbers => numbers.reduce((sum, n) => sum + n, 0) / numbers.length将2个坐标数组作为boundsToRegion，bounds和aspect ratio参数。

示例：

margin

资源：set-the-bounds-of-a-mapview

从边界计算区域

1 个答案: