問題描述

我正在嘗試開發自己的增強現實引擎.

在互聯網上搜索，我發現這個有用的還有另一種獲取beta的實現方式:

- (float)angleFromCoordinate:(CLLocationCoordinate2D)first toCoordinate:(CLLocationCoordinate2D)second {浮動縱向差異 = second.longitude - first.longitude;float latitudinalDifference = second.latitude - first.latitude;浮動可能方位角 = (M_PI * .5f) - atan(latitudinalDifference/longitudinalDifference);if (longitudinalDifference > 0)返回可能的方位角；else if (longitudinalDifference < 0)返回可能的方位角 + M_PI；else if (latitudinalDifference < 0)返回 M_PI；返回 0.0f;}

它使用這個公式:

float possibleAzimuth = (M_PI * .5f) - atan(latitudinalDifference/longitudinalDifference);

為什么 (M_PI * .5f) 在這個公式中?沒看懂.

繼續搜索，我發現另一個頁面在談論如何計算2個位置的距離和方位.在此頁面中還有另一個實現:

/*** 返回從該點到提供點的(初始)方位角，以度為單位* 見 http://williams.best.vwh.net/avform.htm#Crs** @param {LatLon} 點:目標點的緯度/經度* @returns {Number} 初始方位角(以度數為單位)*/LatLon.prototype.bearingTo = 函數(點){var lat1 = this._lat.toRad(), lat2 = point._lat.toRad();var dLon = (point._lon-this._lon).toRad();var y = Math.sin(dLon) * Math.cos(lat2);var x = Math.cos(lat1)*Math.sin(lat2) -Math.sin(lat1)*Math.cos(lat2)*Math.cos(dLon);var brng = Math.atan2(y, x);返回 (brng.toDeg()+360) % 360;}

哪個是正確的?

計算方位

//來源JSONObject 源 = step.getJSONObject("start_location");雙 lat1 = Double.parseDouble(source.getString("lat"));雙 lng1 = Double.parseDouble(source.getString("lng"));//目的地JSONObject 目的地 = step.getJSONObject("end_location");雙 lat2 = Double.parseDouble(destination.getString("lat"));雙 lng2 = Double.parseDouble(destination.getString("lng"));雙 dLon = (lng2-lng1);雙 y = Math.sin(dLon) * Math.cos(lat2);雙倍 x = Math.cos(lat1)*Math.sin(lat2) - Math.sin(lat1)*Math.cos(lat2)*Math.cos(dLon);雙 brng = Math.toDegrees((Math.atan2(y, x)));brng = (360 - ((brng + 360) % 360));

將度數轉換為弧度

弧度 = 度數 * PI/180

將弧度轉換為度數

度數 = 弧度 * 180/PI

I'm trying to develop my own augmented reality engine.

Searching on internet, I've found this useful tutorial. Reading it I see that the important thing is bearing between user location, point location and north.

The following picture is from that tutorial.

Following it, I wrote an Objective-C method to obtain beta:

+ (float) calculateBetaFrom:(CLLocationCoordinate2D)user to:(CLLocationCoordinate2D)destination
{
    double beta = 0;
    double a, b = 0;

    a = destination.latitude - user.latitude;
    b = destination.longitude - user.longitude;

    beta = atan2(a, b) * 180.0 / M_PI;
    if (beta < 0.0)
        beta += 360.0;
    else if (beta > 360.0)
        beta -= 360;

    return beta;
}

But, when I try it, it doesn't work very well.

So, I checked iPhone AR Toolkit, to see how it works (I've been working with this toolkit, but it is so big for me).

And, in ARGeoCoordinate.m there is another implementation of how to obtain beta:

- (float)angleFromCoordinate:(CLLocationCoordinate2D)first toCoordinate:(CLLocationCoordinate2D)second {

    float longitudinalDifference    = second.longitude - first.longitude;
    float latitudinalDifference     = second.latitude  - first.latitude;
    float possibleAzimuth           = (M_PI * .5f) - atan(latitudinalDifference / longitudinalDifference);

    if (longitudinalDifference > 0) 
        return possibleAzimuth;
    else if (longitudinalDifference < 0) 
        return possibleAzimuth + M_PI;
    else if (latitudinalDifference < 0) 
        return M_PI;

    return 0.0f;
}

It uses this formula:

float possibleAzimuth = (M_PI * .5f) - atan(latitudinalDifference / longitudinalDifference);

Why is (M_PI * .5f) in this formula? I don't understand it.

And continue searching, I've found another page talking about how to calculate distance and bearing of 2 locations. In this page there is another implementation:

/**
 * Returns the (initial) bearing from this point to the supplied point, in degrees
 *   see http://williams.best.vwh.net/avform.htm#Crs
 *
 * @param   {LatLon} point: Latitude/longitude of destination point
 * @returns {Number} Initial bearing in degrees from North
 */
LatLon.prototype.bearingTo = function(point) {
  var lat1 = this._lat.toRad(), lat2 = point._lat.toRad();
  var dLon = (point._lon-this._lon).toRad();

  var y = Math.sin(dLon) * Math.cos(lat2);
  var x = Math.cos(lat1)*Math.sin(lat2) -
          Math.sin(lat1)*Math.cos(lat2)*Math.cos(dLon);
  var brng = Math.atan2(y, x);

  return (brng.toDeg()+360) % 360;
}

Which one is the right one?

Calculate bearing

//Source
JSONObject source = step.getJSONObject("start_location");
double lat1 = Double.parseDouble(source.getString("lat"));
double lng1 = Double.parseDouble(source.getString("lng"));

// destination
JSONObject destination = step.getJSONObject("end_location");
double lat2 = Double.parseDouble(destination.getString("lat"));
double lng2 = Double.parseDouble(destination.getString("lng"));

double dLon = (lng2-lng1);
double y = Math.sin(dLon) * Math.cos(lat2);
double x = Math.cos(lat1)*Math.sin(lat2) - Math.sin(lat1)*Math.cos(lat2)*Math.cos(dLon);
double brng = Math.toDegrees((Math.atan2(y, x)));
brng = (360 - ((brng + 360) % 360));

Convert Degrees into Radians

Radians = Degrees * PI / 180

Convert Radians into Degrees

Degrees = Radians * 180 / PI

這篇關于計算兩個位置之間的方位角(緯度、經度)的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！