Calculate compass bearing heading to location in Android

Question

I want to display an arrow at my location on a google map view that displays my direction relative to a destination location  instead of north    a  I have calculated north using the sensor values from the magnetometer and accelerometer  I know this is correct because it lines up with the compass used on the Google Map view   b  I have calculated the initial bearing from my location to the destination location by using myLocation bearingTo destLocation     I m missing the last step  from these two values  a  amp  b  what formula do I use to get the  direction in which the phone is pointing relative to the destination location   Appreciate any help for an addled mind

User · Answer

I m no expert in map-reading   navigation and so on but surely  directions  are absolute and not relative or in reality  they are relative to N or S which themselves are fixed absolute   Example  Suppose an imaginary line drawn between you and your destination corresponds with  absolute  SE  a bearing of 135 degrees relative to magnetic N   Now suppose your phone is pointing NW - if you draw an imaginary line from an imaginary object on the horizon to your destination  it will pass through your location and have an angle of 180 degrees  Now 180 degrees in the sense of a compass actually refers to S but the destination is not  due S  of the imaginary object your phone is pointing at and  moreover  if you travelled to that imaginary point  your destination would still be SE of where you moved to   In reality  the 180 degree line actually tells you the destination is  behind you  relative to the way the phone  and presumably you  are pointing   Having said that  however  if calculating the angle of a line from the imaginary point to your destination  passing through your location  in order to draw a pointer towards your destination is what you want   simply subtract the  absolute  bearing of the destination from the absolute bearing of the imaginary object and ignore a negation  if present   e g   NW - SE is 315 - 135   180 so draw the pointer to point at the bottom of the screen indicating  behind you    EDIT  I got the Maths slightly wrong   subtract the smaller of the bearings from the larger then subtract the result from 360 to get the angle in which to draw the pointer on the screen

User · Answer

I know this is a little old but for the sake of folks like myself from google who didn t find a complete answer here  Here are some extracts from my app which put the arrows inside a custom listview      Location loc      Will hold lastknown location Location wptLoc   new Location            Waypoint location  float dist   -1  float bearing   0  float heading   0  float arrow rotation   0   LocationManager lm    LocationManager  getSystemService Context LOCATION SERVICE   loc   lm getLastKnownLocation LocationManager GPS PROVIDER    if loc    null        No recent GPS fix     Criteria criteria   new Criteria        criteria setAccuracy Criteria ACCURACY FINE       criteria setAltitudeRequired false       criteria setBearingRequired true       criteria setCostAllowed true       criteria setSpeedRequired false       loc   lm getLastKnownLocation lm getBestProvider criteria  true       if loc    null        wptLoc setLongitude cursor getFloat 2         Cursor is from SimpleCursorAdapter     wptLoc setLatitude cursor getFloat 3        dist   loc distanceTo wptLoc       bearing   loc bearingTo wptLoc         -180 to 180     heading   loc getBearing               0 to 360            Code to calculate where the arrow should point         arrow rotation    360   bearing   360    360 -heading    360      I willing to bet it could be simplified but it works  LastKnownLocation was used since this code was from new SimpleCursorAdapter ViewBinder    onLocationChanged contains a call to notifyDataSetChanged     code also from new SimpleCursorAdapter ViewBinder   to set image rotation and listrow colours  only applied in a single columnIndex mind you      LinearLayout ll     LinearLayout view getParent     ll setBackgroundColor bc    int childcount   ll getChildCount    for  int i 0  i  lt  childcount  i         View v   ll getChildAt i       if v instanceof TextView    TextView v  setTextColor fc       if v instanceof ImageView            ImageView img    ImageView v          img setImageResource R drawable ic arrow           Matrix matrix   new Matrix            img setScaleType ScaleType MATRIX           matrix postRotate arrow rotation  img getWidth   2  img getHeight   2           img setImageMatrix matrix        In case you re wondering I did away with the magnetic sensor dramas  wasn t worth the hassle in my case  I hope somebody finds this as useful as I usually do when google brings me to stackoverflow

User · Answer

If you are on the same timezone  Convert GPS to UTM  http   www ibm com developerworks java library j-coordconvert  http   stackoverflow com questions 176137 java-convert-lat-lon-to-utm  UTM coordinates get you a simples X Y 2D  Calculate the angle between both UTM locations  http   forums groundspeak com GC index php showtopic 146917  This gives the direction as if you were looking north  So whatever you rotate related do North just subtract this angle  If both point have a UTM 45   degree angle  and you are 5   east of north  your arrow will point to 40   of north

User · Answer

In this an arrow on compass shows the direction from your location to Kaaba destination Location   you can simple use bearingTo in this way bearing to will give you the direct angle from your location to destination location    Location userLoc new Location  service Provider          get longitudeM Latitude and altitude of current location with gps class and  set in userLoc     userLoc setLongitude longitude        userLoc setLatitude latitude       userLoc setAltitude altitude       Location destinationLoc   new Location  service Provider      destinationLoc setLatitude 21 422487     kaaba latitude setting   destinationLoc setLongitude 39 826206     kaaba longitude setting   float bearTo userLoc bearingTo destinationLoc     bearingTo will give you a range from -180 to 180  which will confuse things a bit  We will need to convert this value into a range from 0 to 360 to get the correct rotation   This is a table of what we really want  comparing to what bearingTo gives us   ----------- --------------    bearingTo   Real bearing    ----------- --------------    0           0               ----------- --------------    90          90              ----------- --------------    180         180             ----------- --------------    -90         270             ----------- --------------    -135        225             ----------- --------------    -180        180             ----------- --------------    so we have to add this code after bearTo     If the bearTo is smaller than 0  add 360 to get the rotation clockwise     if  bearTo  lt  0        bearTo   bearTo   360        bearTo   -100   360    260      you need to implements the SensorEventListener and its functions onSensorChanged onAcurracyChabge  and write all the code inside onSensorChanged   Complete code is here for Direction of Qibla compass   public class QiblaDirectionCompass extends Service implements SensorEventListener   public static ImageView image arrow      record the compass picture angle turned private float currentDegree   0f  private float currentDegreeNeedle   0f  Context context  Location userLoc new Location  service Provider       device sensor manager private static SensorManager mSensorManager   private Sensor sensor  public static TextView tvHeading     public QiblaDirectionCompass Context context  ImageView compass  ImageView needle TextView heading  double longi double lati double alti          image   compass      arrow   needle           TextView that will tell the user what degree is he heading     tvHeading   heading      userLoc setLongitude longi       userLoc setLatitude lati       userLoc setAltitude alti      mSensorManager     SensorManager  context getSystemService SENSOR SERVICE       sensor   mSensorManager getDefaultSensor Sensor TYPE ORIENTATION       if sensor  null               for the system s orientation sensor registered listeners         mSensorManager registerListener this  sensor  SensorManager SENSOR DELAY GAME    SensorManager SENSOR DELAY Fastest      else          Toast makeText context  Not Supported   Toast LENGTH SHORT  show                 initialize your android device sensor capabilities this context  context   Override public void onCreate            TODO Auto-generated method stub     Toast makeText context   Started   Toast LENGTH SHORT  show        mSensorManager registerListener this  sensor  SensorManager SENSOR DELAY GAME     SensorManager SENSOR DELAY Fastest     super onCreate        Override public void onDestroy         mSensorManager unregisterListener this   Toast makeText context   Destroy   Toast LENGTH SHORT  show         super onDestroy        Override public void onSensorChanged SensorEvent sensorEvent      Location destinationLoc   new Location  service Provider     destinationLoc setLatitude 21 422487     kaaba latitude setting destinationLoc setLongitude 39 826206     kaaba longitude setting float bearTo userLoc bearingTo destinationLoc        bearTo   The angle from true north to the destination location from the point we re your currently standing  asal image k N se destination taak angle        head   The angle that you ve rotated your phone from true north   jaise image lagi hai wo true north per hai ab phone jitne rotate yani jitna image ka n change hai us ka angle hai ye     GeomagneticField geoField   new GeomagneticField  Double valueOf  userLoc getLatitude     floatValue    Double          valueOf  userLoc getLongitude     floatValue            Double valueOf  userLoc getAltitude     floatValue            System currentTimeMillis      head -  geoField getDeclination       converts magnetic north into true north  if  bearTo  lt  0        bearTo   bearTo   360        bearTo   -100   360    260       This is where we choose to point it float direction   bearTo - head      If the direction is smaller than 0  add 360 to get the rotation clockwise  if  direction  lt  0        direction   direction   360     tvHeading setText  Heading      Float toString degree      degrees      RotateAnimation raQibla   new RotateAnimation currentDegreeNeedle  direction  Animation RELATIVE TO SELF  0 5f  Animation RELATIVE TO SELF  0 5f   raQibla setDuration 210   raQibla setFillAfter true    arrow startAnimation raQibla    currentDegreeNeedle   direction      create a rotation animation  reverse turn degree degrees  RotateAnimation ra   new RotateAnimation currentDegree  -degree  Animation RELATIVE TO SELF  0 5f  Animation RELATIVE TO SELF  0 5f       how long the animation will take place ra setDuration 210        set the animation after the end of the reservation status ra setFillAfter true       Start the animation image startAnimation ra    currentDegree   -degree     Override public void onAccuracyChanged Sensor sensor  int i        Nullable  Override public IBinder onBind Intent intent        return null      xml code is here    lt  xml version  1 0  encoding  utf-8   gt   lt RelativeLayout xmlns android  http   schemas android com apk res android  android orientation  vertical  android layout width  wrap content  android layout height  wrap content  android background   drawable flag pakistan  gt   lt TextView     android layout width  wrap content      android layout height  wrap content      android id    id heading      android textColor   color colorAccent      android layout centerHorizontal  true      android layout marginBottom  100dp      android layout marginTop  20dp      android text  Heading  0 0    gt   lt RelativeLayout android layout width  wrap content  android layout height  wrap content  android layout below    id heading  android scaleType  centerInside  android layout centerVertical  true  android layout centerHorizontal  true  gt    lt ImageView     android id    id imageCompass      android layout width  wrap content      android layout height  wrap content      android scaleType  centerInside      android layout centerVertical  true      android layout centerHorizontal  true      android src   drawable images compass   gt    lt ImageView     android id    id needle      android layout width  wrap content      android layout height  wrap content      android layout centerVertical  true      android layout centerHorizontal  true      android scaleType  centerInside      android src   drawable arrow2   gt   lt  RelativeLayout gt   lt  RelativeLayout gt

User · Answer

Here is how I have done it   Canvas g   new Canvas  compass    Paint p   new Paint  Paint ANTI ALIAS FLAG     float rotation   display getOrientation     90   g translate  -box left  -box top    g rotate  -bearing - rotation  box exactCenterX    box exactCenterY      drawCompass  g  p    drawNeedle  g  p

User · Answer

This is the best way to detect Bearing from Location Object on Google Map -    float targetBearing 90         Location endingLocation new Location  ending point            Location        startingLocation new Location  starting point           startingLocation setLatitude mGoogleMap getCameraPosition   target latitude          startingLocation setLongitude mGoogleMap getCameraPosition   target longitude          endingLocation setLatitude mLatLng latitude          endingLocation setLongitude mLatLng longitude         targetBearing          startingLocation bearingTo endingLocation

User · Answer

I am in the process of figuring it out now but it seems as though the math depends on where you and your target are on the earth relative to true and magnetic North  For example     float thetaMeThem   0 0  if  myLocation bearingTo targetLocation   gt  myLocation getBearing           thetaMeThem   myLocation bearingTo targetLocation  - azimuth   declination      See    Sensor TYPE ORIENTATION for azimuth   See    getDeclination   for declination  This assumes declination is negative  west of true north  and theirBearing   yourBearing   If declination is positive and yourBearing   theirBearing another option   float thetaMeThem   0 0  if  myLocation bearingTo targetLocation   lt  myLocation getBearing           thetaMeThem   azimuth -  myLocation bearingTo targetLocation  - declination       I haven t tested this fully but playing with the angles on paper got me here

User · Answer

Ok I figured this out  For anyone else trying to do this you need   a  heading  your heading from the hardware compass  This is in degrees east of magnetic north  b  bearing  the bearing from your location to the destination location   This is in degrees east of true north   myLocation bearingTo destLocation     c  declination  the difference between true north and magnetic north  The heading that is returned from the magnetometer   accelermometer is in degrees east of true  magnetic  north  -180 to  180  so you need to get the difference between north and magnetic north for your location   This difference is variable depending where you are on earth   You can obtain by using GeomagneticField class   GeomagneticField geoField   private final LocationListener locationListener   new LocationListener        public void onLocationChanged Location location          geoField   new GeomagneticField           Double valueOf location getLatitude    floatValue             Double valueOf location getLongitude    floatValue             Double valueOf location getAltitude    floatValue             System currentTimeMillis                               Armed with these you calculate the angle of the arrow to draw on your map to show where you are facing in relation to your destination object rather than true north   First adjust your heading with the declination   heading    geoField getDeclination      Second  you need to offset the direction in which the phone is facing  heading  from the target destination rather than true north  This is the part that I got stuck on  The heading value returned from the compass gives you a value that describes where magnetic north is  in degrees east of true north  in relation to where the phone is pointing  So e g  if the value is -10 you know that magnetic north is 10 degrees to your left   The bearing gives you the angle of your destination in degrees east of true north  So after you ve compensated for the declination you can use the formula below to get the desired result   heading   myBearing -  myBearing   heading      You ll then want to convert from degrees east of true north  -180 to  180  into normal degrees  0 to 360    Math round -heading   360   180

User · Answer

Terminology   The difference between TRUE north and Magnetic North is known as  variation  not declination   The difference between what your compass reads and the magnetic heading is known as  deviation  and varies with heading   A compass swing identifies device errors and allows corrections to be applied if the device has correction built in   A magnetic compass will have a deviation card which describes the device error on any heading   Declination    A term used in Astro navigation   Declination is like latitude  It reports how far a star is from the celestial equator  To find the declination of a star follow an hour circle  straight down  from the star to the celestial equator  The angle from the star to the celestial equator along the hour circle is the star s declination

User · Answer

The formula will give the bearing using the coordinates of the start point to the end point see   The following code will give you the bearing  angle between 0-360   private double bearing Location startPoint  Location endPoint        double longitude1   startPoint getLongitude        double latitude1   Math toRadians startPoint getLatitude          double longitude2   endPoint getLongitude                double latitude2   Math toRadians endPoint getLatitude          double longDiff   Math toRadians longitude2 - longitude1        double y   Math sin longDiff    Math cos latitude2       double x   Math cos latitude1    Math sin latitude2  - Math sin latitude1    Math cos latitude2    Math cos longDiff        return Math toDegrees Math atan2 y  x         This works for me hope it will work others as well

User · Answer

Damian - The idea is very good and I agree with answer  but when I used your code I had wrong values  so I wrote this on my own  somebody told the same in your comments   Counting  heading with the declination is good  I think  but later I used something like that   heading    bearing - heading    -1    instead of Damian s code   heading   myBearing -  myBearing   heading      and changing -180 to 180 for 0 to 360         private float normalizeDegree float value             if value  gt   0 0f  amp  amp  value  lt   180 0f                 return value             else                return 180    180   value                 and then when you want to rotate your arrow you can use code like this         private void rotateArrow float angle                Matrix matrix   new Matrix                arrowView setScaleType ScaleType MATRIX               matrix postRotate angle  100f  100f               arrowView setImageMatrix matrix             where arrowView is ImageView with arrow picture and 100f parameters in postRotate is pivX and pivY    I hope I will help somebody

[android] Calculate compass bearing / heading to location in Android

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