如何单独使用GPS读数确定方向并以360度显示？

Question

我正在开发AS3 AIR for Android应用程序."我的问题是:给定一个GPS位置,我想找回运动方向(北,西,西,西南,南,东,东,东北)"

我想要如何使用2个不同的GPS读数来推断出旅行方向的代码.然后我想将这些数据用于360度.

我想我理解如何获得像北方,南方,东方和西方这样的大方向.我会获得2个独立的GPS读数并比较类似的东西......

查看第一次或第二次GPS读数中X是否更大.在第一次或第二次GPS读数中查看Y是否更大.由此我应该能够看到总体方向.比较X1和X2的差异与Y1和Y2的差异.那么你可以看到用户最多的方向.然后显示方向.

我不确定如何获取数据并将其用于像罗盘一样的360解释......任何人都可以帮忙吗？

工作代码------------------------------------------------ -------------------------------

package 

{
import flash.display.Sprite;
// Geolocation sensor stuff
import flash.sensors.Geolocation; 
import flash.events.GeolocationEvent;
//Timer setup stuff for setting frequesncy of GPS Update
import flash.utils.Timer;
import flash.events.TimerEvent;

// Sprite and Textfield display
import flash.display.Sprite;
import flash.text.TextField;
import flash.text.TextFieldAutoSize;
import flash.text.TextFormat;


    public class FlashTest extends Sprite 

    {
        //Variable to check if current or prior Geolocation Event fired
        private var gpsCheck:int = 1;
        public var dLon:Number


        //latitude and longitude in degrees (RAW info from Geolocation)
        public var gpsLat1:Number
        public var gpsLon1:Number
        private var gpsLat2:Number
        private var gpsLon2:Number
        public var bearing:Number


        // Latitude and longitude in radians converted from Degrees
        public var gpsLat1R:Number
        public var gpsLon1R:Number
        private var gpsLat2R:Number
        private var gpsLon2R:Number     
        private var yy:Number  
        private var xx:Number          


        public function FlashTest() 

        {
            // Text box for displaying results
            var my_txt:TextField = new TextField();
                my_txt.wordWrap=true; 
                my_txt.width = 300;
                my_txt.height = 300;
                 addChild(my_txt);

            /*
            //If GPS is on device create Geolocation object named "my_geo"
            //Request updates from my_geo every 2000 milliseconds. Run onGeoUpdate function
            //when Event is triggered. After that create the text box for displaying data.
            if (Geolocation.isSupported)
            {
                var my_geo:Geolocation = new Geolocation();
                my_geo.setRequestedUpdateInterval(2000);                
                my_geo.addEventListener(GeolocationEvent.UPDATE, onGeoUpdate);
                var my_txt:TextField = new TextField();
                my_txt.wordWrap=true; 
                my_txt.width = 300;
                my_txt.height = 300;
                addChild(my_txt);
            } 
            // If GPS is not supported on device display "No GPS Signal" 
            else
            {
                addChild(my_txt);
                my_txt.wordWrap=true; 
                my_txt.width = 300;
                my_txt.height = 300;
                addChild(my_txt);
                my_txt.text = "No GPS Signal ";
            }
            */


            // False GPS reading being passed for testing 
            //COMMENT THESE LINES OUT STARTING HERE---
                gpsLat1 =  42.1234584;
                gpsLon1 = -83.1234577;
                gpsLat2 =  42.1234583;
                gpsLon2 = -83.1234577;
           // END OF WHAT SHOULD BE COMMENTED OUT---

           // Equations to convert all RAW Geolocation information over to radians 
                gpsLat1R = gpsLat1 * Math.PI / 180;
                gpsLon1R = gpsLon1 * Math.PI / 180;
                gpsLat2R = gpsLat2 * Math.PI / 180;
                gpsLon2R = gpsLon2 * Math.PI / 180;
          // The rest of the math     
                dLon = gpsLon1 - gpsLon2;
                yy = Math.sin(dLon) * Math.cos(gpsLat2R);
                xx = Math.cos(gpsLat1R) * Math.sin(gpsLat2R) - Math.sin(gpsLat1R) * Math.cos(gpsLat2R) * Math.cos(dLon);
                bearing = Math.atan2(yy, xx) * 180 / Math.PI;
         // Run The Geoupdate function                
            onGeoUpdate();


        // onGeoUpdate basically displays the information that was collected and converted.
        // This is where you will put what you want the code to do with the results
            function onGeoUpdate():void
            {
            my_txt.text = "My Latitude is "+gpsLat1+ " and my Longitude is "+gpsLon1+ 
            "My 2nd Latitude is "+gpsLat2+" and my 2nd Longitude is "+gpsLon2+ 
            " Bearing is " +bearing;

            }            
        }
    }
}

Answer 1

你需要的公式(对lon1,lon2经度,并且lat1,lat2这两个点的纬度)被赋予在许多地方-例如,在http://www.movable-type.co.uk/scripts/latlong.html.数学是这样的(将其转换为您最喜欢的语言......):

dLon = lon2 - lon1;
y = sin(dLon) * cos(lat2);
x = cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) *cos(dLon);
bearing = atan2(y, x) * 180 / Pi;

注意:atan2将结果减小到[-pi,pi]之间的值.乘以180/pi数后将在[-180,180]之间.为了获得0到360之间的值,您可以这样做,例如:

if (bearing < 0) bearing += 360;

我希望您能填写您需要的任何其他详细信息,以便为您服务.

编辑我已经使用你给出的数字来编写一些代码:这是Matlab,但它应该是非常可读的:

% bearings
lat1 = 42.1234584;
lat2 = 42.1234583;
lon1 = -83.1234577;
lon2 = -83.1234510;

% convert to radians:
g2r = pi/180;
lat1r = lat1 * g2r;
lat2r = lat2 * g2r;
lon1r = lon1 * g2r;
lon2r = lon2 * g2r;
dlonr = lon2r - lon1r;
y = sin(dlonr) * cos(lat2r);
x = cos(lat1r)*sin(lat2r) - sin(lat1r) * cos(lat2r)*cos(dlonr);

% compute bearning and convert back to degrees:
bearing = atan2(y, x) / g2r;

fprintf(1,'x: %+.3e\ny: %+.3e\nbearing: %.3f\n', x, y, bearing);

这导致输出:

x: -1.745e-09
y: +8.673e-08
bearing: 91.153

正如你所看到的,x并且y是微小的-他们所代表的是你移动(由于约3.5米,东,似乎...)"地球周长的分数".您应该能够使用这些数字调试您的实现.

请注意GPS可能具有较差的"绝对"精度(在您的情况下,不确定度> 100 m),但仍具有良好的"相对"精度(它测量两个位置之间的差异远优于100 m).