Android中的GPS区域 [英] GPS area in Android

问题描述

GPS面积计算有什么类吗?

Is there any class for GPS area calculate?

推荐答案

我用这段代码用 Android 计算由 GPS 点划分的区域:

I use this code to calculate an area delimited by GPS points with Android:

  private static final double EARTH_RADIUS = 6371000;// meters

  public static double calculateAreaOfGPSPolygonOnEarthInSquareMeters(final List<Location> locations) {
    return calculateAreaOfGPSPolygonOnSphereInSquareMeters(locations, EARTH_RADIUS);
  }

  private static double calculateAreaOfGPSPolygonOnSphereInSquareMeters(final List<Location> locations, final double radius) {
    if (locations.size() < 3) {
      return 0;
    }

    final double diameter = radius * 2;
    final double circumference = diameter * Math.PI;
    final List<Double> listY = new ArrayList<Double>();
    final List<Double> listX = new ArrayList<Double>();
    final List<Double> listArea = new ArrayList<Double>();
    // calculate segment x and y in degrees for each point
    final double latitudeRef = locations.get(0).getLatitude();
    final double longitudeRef = locations.get(0).getLongitude();
    for (int i = 1; i < locations.size(); i++) {
      final double latitude = locations.get(i).getLatitude();
      final double longitude = locations.get(i).getLongitude();
      listY.add(calculateYSegment(latitudeRef, latitude, circumference));
      Log.d(LOG_TAG, String.format("Y %s: %s", listY.size() - 1, listY.get(listY.size() - 1)));
      listX.add(calculateXSegment(longitudeRef, longitude, latitude, circumference));
      Log.d(LOG_TAG, String.format("X %s: %s", listX.size() - 1, listX.get(listX.size() - 1)));
    }

    // calculate areas for each triangle segment
    for (int i = 1; i < listX.size(); i++) {
      final double x1 = listX.get(i - 1);
      final double y1 = listY.get(i - 1);
      final double x2 = listX.get(i);
      final double y2 = listY.get(i);
      listArea.add(calculateAreaInSquareMeters(x1, x2, y1, y2));
      Log.d(LOG_TAG, String.format("area %s: %s", listArea.size() - 1, listArea.get(listArea.size() - 1)));
    }

    // sum areas of all triangle segments
    double areasSum = 0;
    for (final Double area : listArea) {
      areasSum = areasSum + area;
    }

    // get abolute value of area, it can't be negative
    return Math.abs(areasSum);// Math.sqrt(areasSum * areasSum);
  }

  private static Double calculateAreaInSquareMeters(final double x1, final double x2, final double y1, final double y2) {
    return (y1 * x2 - x1 * y2) / 2;
  }

  private static double calculateYSegment(final double latitudeRef, final double latitude, final double circumference) {
    return (latitude - latitudeRef) * circumference / 360.0;
  }

  private static double calculateXSegment(final double longitudeRef, final double longitude, final double latitude,
      final double circumference) {
    return (longitude - longitudeRef) * circumference * Math.cos(Math.toRadians(latitude)) / 360.0;
  }

您可以轻松地将其适应 java，而不是使用位置对象列表，而是使用两个纬度和经度列表.

You can easily adapt it to java not using a list of location objects but two list of latitudes and longitudes.

这是基于这个公式:

http://mathworld.wolfram.com/PolygonArea.html

这里也有描述:

http://en.wikipedia.org/wiki/Polygon

用这个公式计算多边形面积的原理:

Principle of ploygon area calculation with this formula:

http://maruzar.blogspot.com/2011/12/irregular-and-regular-polygon-area-by.html

公式适用于球体上的区域，在我们的例子中是世界球体，以及计算的 excel 示例对于验证您在 Java 或其他语言中的算法非常有用:

Formula adapted to area on a sphere, in our case the world sphere, and excel example of the calculation very usefull to verify your algorithm in Java or other language:

http://maruzar.blogspot.com/2012/03/calculating-land-lot-area-with-gps.html

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