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)#Rotation_matrix_.E2.86.94_Euler_angles
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 [email protected]
To unsubscribe from this group, send email to
[email protected]
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.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/android-developers?hl=en
