this works for me: 1: listen to location changes. Store the most recent location. You need it below. 2: listen to orientation changes. Store the most recent heading (azimuth) in mHeading - that's the compass direction corresponding to your viewing direction when holding your phone horizontally in portrait mode; 3: the bearing to your destination (assuming you have its coordinates) can be found using Location.distanceBetween() (call it mBearing) 4: to point your directional arrow towards the destination, its required rotation (from 'up') is ((mBearing - mHeading)+360) % 360;
You may wish to compensate for device rotation (portrait/landscape), too. See Display.getOrientation / Display.getRotation Not a complete 3D solution, but works ok. /Per (not sure if the terms bearing/heading are 100% in sync with common naval use, but hey...) On 22 Sep., 11:28, Kostya Vasilyev <kmans...@gmail.com> wrote: > Pedro, > > I think you should learn something about the way direction (and > orientation) is specified in computer programming. > > http://en.wikipedia.org/wiki/Yaw,_pitch,_and_roll > > http://en.wikipedia.org/wiki/Euler_angles > > http://en.wikipedia.org/wiki/Rotation_representation_(mathematics)#Ro... > > I believe that Android orientation sensors work this way. > > Now about the compass.... > > There are two ways you can think about this: > > First, take the value you get from the algorithm and make it into a > vector in 3D space (i.e. think of the arrow you're going to draw to > indicate direction). Then: > > One: Compute the device's orientation matrix using sensor data. Take the > inverse of this matix, and multiply the "arrow" vector by this matrix. > > Two: Compute the device's orientation matrix using sensor data. Rather > than interpreting it as a rotation matrix, think of it as defining a > plane in space (aligned with the device's screen). Then project the > "arrow" vector onto this plane, in the plane's coordinates. > > You might want to start with compensating just for the vertical axis > (the device's rotation from the true north direction), it might be enough. > > -- Kostya > > 22.09.2010 13:02, Pedro Teixeira пишет: > > > > > > > I'm really not understanding how to go with this... > > > I've been reading and reading.. I can find all kind of algorithms.. I > > can find a haversin algorithm that points me to the correct direction > > if my device is pointing north.. but the needle is static... so if i > > change the device orientation the measure is incorrect... and I know > > this happens because I'm not using device's sensor values like > > azimuth, pitch and roll.. oh god.. 2 weeks on this.. I'm just > > desperate now. > > > On Sep 18, 2010, at 10:29 AM, Kostya Vasilyev wrote: > > >> Pedro, > > >> If I understand you correctly, you are having difficulties with the > >> device's orientation. > > >> The bearing angle seems to be computed in the horizontal plane. If > >> you wish to adjust for the device's orientation, you need to > >> concatenate it with the bearing angle. > > >> Google for "quaternions". > > >> This is a (relatively) simple math technique to work with rotations > >> the same way you can work with vectors: add / subtract, interpolate. > > >> -- Kostya > > >> 18.09.2010 0:56, Pedro Teixeira пишет: > >>> Hi everyone... > > >>> I'm back with the same issue for the last couple of days… I'm trying > >>> to create a compass for my application BUT the difference is that, > >>> instead of having a line always pointing to north, I want this line to > >>> point for a specific point. I've been trying dozens of algorithms and > >>> nothing works.. > >>> I've finally found one that points me exactlly to the point I want.. > >>> BUT it doesn't move if I change the position of the device which is my > >>> objective.. basicly, what I want is that no matter the direction I'm > >>> using my device.. the line always point me to the point > >>> (picLatitude,picLongitude)… > > >>> I understood that for the line to move, I can't use static variables… > >>> I need to use the values offered by the onSensorChanged(SensorEvent > >>> event). > > >>> This are the data I have available: > > >>> event.values[0]: azimuth, rotation around the Z axis (device in > >>> relation to north, 0º) > >>> event.values[1]: pitch, rotation around the X axis > >>> event.values[2]: roll, rotation around the Y axis > >>> mLatitude: device current latitude gottern from GPS (variable) > >>> mLongitude: device current longitude gotten from GPS (variable) > >>> picLatitude: static picture latitude established previously > >>> picLongitude: static picture longitude established previously > >>> distance: distance in Km from device to the picture calculated > >>> previously > > >>> And this the formula that works correct, and gives me the correct > >>> angle.. ( BUT IT DOESN'T USE ANY OF THE SENSOR DATA SO THE LINE > >>> COMPASS DOESNT MOVE): > > >>> double dLong = picLongitude - mLongitude; > >>> double y = (Math.sin(dLong) * Math.cos(picLatitude)); > >>> double x = (Math.cos(mLatitude) * Math.sin(picLatitude) - > >>> Math.sin(mLatitude)*Math.cos(picLatitude)*Math.cos(dLong)); > >>> double angleDegreesWrongRange = Math.abs(Math.toDegrees(Math.atan2(y, > >>> x))); > >>> float angleDegrees = (float) ((angleDegreesWrongRange+360) % 360); > > >>> myCompass.updateDirection(angleDegrees); > > >>> I got this "bearing" formula from this website: > >>>http://www.movable-type.co.uk/scripts/latlong.html > > >>> Can someone please help me with this? > >>> I've try adding, subtracting… the azimuth.. I've tried with the > >>> others.. seriously at this point I'm just demoralized.. > > >>> Thank you in advance > > >> -- > >> Kostya Vasilyev -- WiFi Manager + pretty widget -- > >>http://kmansoft.wordpress.com > > >> -- > >> You received this message because you are subscribed to the Google > >> Groups "Android Developers" group. > >> To post to this group, send email to android-developers@googlegroups.com > >> To unsubscribe from this group, send email to > >> android-developers+unsubscr...@googlegroups.com > >> For more options, visit this group at > >>http://groups.google.com/group/android-developers?hl=en > > > Pedro Teixeira > > >www.pedroteixeira.org > > -- > Kostya Vasilyev -- WiFi Manager + pretty widget > --http://kmansoft.wordpress.com -- You received this message because you are subscribed to the Google Groups "Android Developers" group. 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