javascript - 获取 Google Static Maps API 的西南 Angular 和东北 Angular

Question

我在 Unity 应用程序中获取 Google 静态 map 的边界时遇到问题。我尝试了在 stackoverflow 上找到的多个答案。

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Javascript related question

我要计算 Angular 点的 map 是 this map 。

首先，我尝试将 marcelo 他的代码从 javascript 翻译成 C#。翻译成下面的类。

using System;
using UnityEngine;
public class MercatorProjection
{
    static double MERCATOR_RANGE = 256;
    Point pixelsOrigin;
    double pixelsPerLonDegree;
    double pixelsPerLonRadian;

    public MercatorProjection()
    {
        pixelsOrigin = new Point(MERCATOR_RANGE / 2, MERCATOR_RANGE / 2);
        pixelsPerLonDegree = MERCATOR_RANGE / 360;
        pixelsPerLonRadian = MERCATOR_RANGE / (2 * Math.PI);
    }

    double bound(double value, double opt_min, double opt_max)
    {
        if (opt_min != 0)
            value = Math.Max(value, opt_min);
        if (opt_max != 0)
            value = Math.Min(value, opt_max);
        return value;
    }

    double degreesToRadians(double deg)
    {
        return deg * (Math.PI / 180);
    }

    double radiansToDegrees(double rad)
    {
        return rad / (Math.PI / 180);
    }

    Point fromLatLonToPoint(Coordinates latLon)
    {
        Point point = new Point();
        Point origin = pixelsOrigin;

        point.X = origin.X + latLon.Longitude * pixelsPerLonDegree;

        double sinY = bound(Math.Sin(degreesToRadians(latLon.Latitude)), -0.9999, 0.9999);

        point.Y = origin.Y + 0.5 * Math.Log((1 + sinY) / (1 - sinY)) * -pixelsPerLonRadian;

        return point;
    }

    Coordinates fromPointToLatlon(Point point)
    {
        Point origin = pixelsOrigin;
        Coordinates latLon = new Coordinates();

        latLon.Latitude = (point.X - origin.X) / pixelsPerLonDegree;
        double latRadians = (point.Y - origin.Y) / -pixelsPerLonRadian;
        latLon.Longitude = radiansToDegrees(2 * Math.Atan(Math.Exp(latRadians)) - Math.PI / 2);

        return latLon;
    }

    public void GetCorners(Coordinates center, float zoom, float mapWidth, float mapHeight)
    {
        double scale = Math.Pow(2, zoom);
        Point centerPx = fromLatLonToPoint(center);
        Point SWPoint = new Point(centerPx.X - (mapWidth / 2) / scale, centerPx.Y + (mapHeight / 2) / scale);
        Coordinates SWLatLon = fromPointToLatlon(SWPoint);
        Debug.Log(SWLatLon.Latitude + " " + SWLatLon.Longitude + " " + SWPoint.X + " " + SWPoint.Y);
    }
}

所以起初我只尝试获取 map 的西南 Angular ，它非常接近，但有点偏离。

MercatorProjection.GetCorners(new Coordinates(Coordinates.Longitude, Coordinates.Latitude), 16, 640, 640);

给我带来了 this 结果。

因为有这么多人投票，首先我尝试翻译 marcelo 他的回答，我想我在将代码翻译成 C# 的过程中做错了什么。

然后我偶然发现了 peterjb's answer，他已经将 javascript 答案翻译成 C#，甚至给出了示例，其中他的代码获得了 Google 静态 map 的正确边界。所以在下面的类中尝试 peterjb 的代码之后；

using System;

public static class GoogleMapsAPI{

    static GoogleMapsAPI()
    {
        OriginX = TileSize / 2;
        OriginY = TileSize / 2;
        PixelsPerLonDegree = TileSize / 360.0;
        PixelsPerLonRadian = TileSize / (2 * Math.PI);
    }

    public static int TileSize = 256;
    public static double OriginX, OriginY;
    public static double PixelsPerLonDegree;
    public static double PixelsPerLonRadian;

    public static double DegreesToRadians(double deg)
    {
        return deg * Math.PI / 180.0;
    }

    public static double RadiansToDegrees(double rads)
    {
        return rads * 180.0 / Math.PI;
    }

    public static double Bound(double value, double min, double max)
    {
        value = Math.Min(value, max);
        return Math.Max(value, min);
    }

    //From Lat, Lon to World Coordinate X, Y. I'm being explicit in assigning to
    //X and Y properties.
    public static Coordinate Mercator(double latitude, double longitude)
    {
        double siny = Bound(Math.Sin(DegreesToRadians(latitude)), -.9999, .9999);

        Coordinate c = new Coordinate(0, 0);
        c.X = OriginX + longitude * PixelsPerLonDegree;
        c.Y = OriginY + .5 * Math.Log((1 + siny) / (1 - siny)) * -PixelsPerLonRadian;

        return c;
    }

    //From World Coordinate X, Y to Lat, Lon. I'm being explicit in assigning to
    //Latitude and Longitude properties.
    public static Coordinate InverseMercator(double x, double y)
    {
        Coordinate c = new Coordinate(0, 0);

        c.Longitude = (x - OriginX) / PixelsPerLonDegree;
        double latRadians = (y - OriginY) / -PixelsPerLonRadian;
        c.Latitude = RadiansToDegrees(Math.Atan(Math.Sinh(latRadians)));

        return c;
    }

    public static MapCoordinates GetBounds(Coordinate center, int zoom, int mapWidth, int mapHeight)
    {
        var scale = Math.Pow(2, zoom);

        var centerWorld = Mercator(center.Latitude, center.Longitude);
        var centerPixel = new Coordinate(0, 0);
        centerPixel.X = centerWorld.X * scale;
        centerPixel.Y = centerWorld.Y * scale;

        var NEPixel = new Coordinate(0, 0);
        NEPixel.X = centerPixel.X + mapWidth / 2.0;
        NEPixel.Y = centerPixel.Y - mapHeight / 2.0;

        var SWPixel = new Coordinate(0, 0);
        SWPixel.X = centerPixel.X - mapWidth / 2.0;
        SWPixel.Y = centerPixel.Y + mapHeight / 2.0;

        var NEWorld = new Coordinate(0, 0);
        NEWorld.X = NEPixel.X / scale;
        NEWorld.Y = NEPixel.Y / scale;

        var SWWorld = new Coordinate(0, 0);
        SWWorld.X = SWPixel.X / scale;
        SWWorld.Y = SWPixel.Y / scale;

        var NELatLon = InverseMercator(NEWorld.X, NEWorld.Y);
        var SWLatLon = InverseMercator(SWWorld.X, SWWorld.Y);

        return new MapCoordinates() { NorthEast = NELatLon, SouthWest = SWLatLon };
    }
}
public class MapCoordinates
{
    public Coordinate SouthWest { get; set; }
    public Coordinate NorthEast { get; set; }
}

public class Coordinate
{
    public double Latitude { get; set; }
    public double Longitude { get; set; }

    public double Y { get { return Latitude; } set { Latitude = value; } }
    public double X { get { return Longitude; } set { Longitude = value; } }

    public Coordinate(double lng, double lat)
    {
        Latitude = lat;
        Longitude = lng;
    }

    public override string ToString()
    {
        return Math.Round(X, 6).ToString() + ", " + Math.Round(Y, 6).ToString();
    }
}

我尝试通过调用以下命令再次计算 SW 和 NE Angular

Coordinates = new Coordinate(51.445691, 5.460318);
var result = GoogleMapsAPI.GetBounds(Coordinates, 16, 640, 640);
Debug.Log("SouthWest: "+result.SouthWest.ToString() + " NorthEast: "+result.NorthEast.ToString());

输出:

SouthWest: 51.438825, 5.453483 NorthEast: 51.452557, 5.467153

SouthWest 坐标与我自己翻译的 javascript 完全相同。因此，由于 peterjb 在他的回答中声称他的解决方案适用于比利时的某个地区，所以我在同一地区尝试了代码。然而，结果又有点不对劲。

因此，我非常随机地尝试使用尼日利亚一个名为 Kano/Static map 的城镇的计算，令我惊讶的是，西南 Angular 非常准确!

输出:

SouthWest: 12.015251, 8.527824 NorthEast: 12.028983, 8.541404

SouthWest position .

之后，我尝试了世界上其他多个地区，但往往距离很远，有时甚至数百英里。所以也许尼日利亚的这个小镇只是巧合，但我希望有人能为我提供解释和/或解决方案。

特别感谢 peterjb 和 marcelo

Answer 1

Coordinate 类的构造函数接受 (lng, lat) 而不是您可能期望的 (lat, lng)，因此参数的顺序与您传入的顺序不同。

我还注意到 Coordinate 的 ToString 也覆盖打印为 (lng, lat)，因此如果您希望看到 (lat, lng) 可能会造成混淆。

只需在静态 API 中交换这两者即可。