Yes suposselly:
The rotation in degree can be retrieved from event.values[0],
event.values[1] and event.values[2].
event.values[0]: azimuth, rotation around the Z axis.
event.values[1]: pitch, rotation around the X axis.
event.values[2]: roll, rotation around the Y axis.
So I'm getting the value in degrees.
With that algorithm I'm assuming, my device position in relation to
the point I want to calcutate position, and subtracting my device
orientation to the north, so that the algorythm always has as
reference ''0''
I don't know if this makes any sense, but im having a hard time
finding information.. to worst things up, english is not my mother
language so specific terms about navigation and trigonometry are very
hard for me lol
On Sep 16, 2010, at 8:13 PM, DanH wrote:
This is why I suggest you prototype it as a desktop "toy" program in
plain Java. You can feed in numbers and see what you get out -- see
if the numbers make sense. You can even plot them out on a map to
verify them.
Re the formula, it looks to be approximately correct (assuming
"values" is in degrees). When dealing with compass points there's
always the issue of where the zero origin is, and whether you're going
+ or -, but those are nits to work out.
You do have a basic (but not fatal) error in that the formula is only
really accurate when you're near the equator and the two points are
relatively close together. Near a pole the result would be off
(pointing too far east or west). But the amount of error below, say,
the 50th parallel would be fairly small -- less than "eyeball"
accuracy in most cases.
(And of course it's questionable as to how accurate the compass in the
device is in the first place. Even if it's auto-corrected for
magnetic declination, a small magnetic compass is subject to
substantial interference from nearby objects.)
On Sep 16, 1:58 pm, Pedro Teixeira <[email protected]> wrote:
I'm actually not positivlly sure about the algorythm since it will
return always the same value if I'm on the same position... so it
doesn't make sense because it should depend on the device
orientation... I'm using now the azimuth.. because it will depend on
the orientation of the device.. at least the line is moving.. I guess
is just a mathematical thing now ..ohh the math :S
float angleDegrees = (float) Math.abs(Math.toDegrees(Math.atan2
(picLongitude-mLongitude, picLatitude-mLatitude))-event.values[0]);
On Sep 16, 2010, at 5:41 PM, DanH wrote:
Have you done any debugging? Looked at the raw sensor readings to
make sure they make sense? Implemented the algorithm in Java on a
desktop, fed in sensor numbers, and checked whether it produced what
you expected?
On Sep 16, 11:26 am, Pedro Teixeira <[email protected]>
wrote:
Hi everyone..I'm trying to implement spomething that I don't even
know
if it's possible..
So I have this class which implements a SensorEventListener like
this:
private SensorEventListener mySensorEventListener = new
SensorEventListener(){
@Override
public void onAccuracyChanged(Sensor sensor, int
accuracy) {
}
@Override
public void onSensorChanged(SensorEvent event) {
myCompass.updateDirection((float)event.values[0]);
}
};
And a class that handles the way the compass looks like this:
public static class compassLook extends View {
private Paint paintPointer = new Paint
(Paint.ANTI_ALIAS_FLAG);
private Paint paintCircle = new Paint
(Paint.ANTI_ALIAS_FLAG);
private Paint paintLeters = new Paint
(Paint.ANTI_ALIAS_FLAG);
private boolean firstDraw;
private float direction = 0 ;
public compassLook(Context context) {
super(context);
init();
}
public compassLook(Context context, AttributeSet
attrs) {
super(context, attrs);
init();
}
public compassLook(Context context, AttributeSet
attrs, int
defStyle) {
super(context, attrs, defStyle);
init();
}
private void init(){
paintPointer.setStyle(Paint.Style.STROKE);
paintPointer.setStrokeWidth(3);
paintPointer.setColor(Color.argb(255, 209, 114,
2));
paintCircle.setStyle(Paint.Style.STROKE);
paintCircle.setStrokeWidth(2);
paintCircle.setColor(Color.argb(150, 255, 255,
255));
paintLeters.setStyle(Paint.Style.STROKE);
paintLeters.setStrokeWidth(1);
paintLeters.setColor(Color.argb(230, 255, 255,
255));
paintLeters.setTextSize(12);
firstDraw = true;
}
@Override
protected void onMeasure(int widthMeasureSpec, int
heightMeasureSpec) {
setMeasuredDimension(MeasureSpec.getSize
(widthMeasureSpec),
MeasureSpec.getSize(heightMeasureSpec));
}
@Override
protected void onDraw(Canvas canvas) {
int cxCompass = (getMeasuredWidth()/2);
int cyCompass = (getMeasuredHeight()/2);
float radiusCompass;
if(cxCompass > cyCompass){
radiusCompass = (float) (cyCompass * 0.9);
}
else{
radiusCompass = (float) (cxCompass * 0.9);
}
canvas.drawCircle(cxCompass-50, cyCompass,
radiusCompass,
paintCircle);
if(!firstDraw){
// Desenho da linha que aponta
canvas.drawLine(cxCompass-50, cyCompass,
(float)(cxCompass-50 + radiusCompass * Math.sin
((double)(-
direction) * 3.14/180)),
(float)(cyCompass - radiusCompass * Math.cos
((double)(-direction)
* 3.14/180)),
paintPointer);
double mLatitude = (mLocation.getLatitude() /
1E6); // I get this
value from a LM request
double mLongitude = (mLocation.getLongitude() /
1E6); // I get this
value from a LM request
double picLatitude = Double.parseDouble
(picLatitudeString); // I get
this value from a bundle
double picLongitude = Double.parseDouble
(picLongitudeString); // I
get this value from a bundle
float direction = (float) Math.toDegrees(Math.atan2
(picLongitude-
mLongitude, picLatitude-mLatitude));
float distancia = (float) (Math.sqrt
(Math.pow(mLatitude-
picLatitude, 2) + Math.pow(mLongitude-picLongitude,2)))/2;
//Desenho do texto que indica a distancia
canvas.drawText(String.valueOf(distancia) + "Km",
cxCompass-30,
cyCompass+20, paintLeters);
}
}
public void updateDirection(float dir)
{
firstDraw = false;
direction = dir;
invalidate();
}
}
This classes work perfectlly showing me a little circle with a line
pointing the North.
What I would like to do, is ..given this 2 points in space
(mLatitude,
mLongitude) and (picLatitude, picLongitude) which are the user
position, and a certain picture position. I'd like the compass to
point to the position of the picture (picLatitude,picLongitude)
from
the position they are in the moment (mLatitude,mLongitude)
I came to the trignometry formula that calculates this..being:
float direction = (float) Math.toDegrees(Math.atan2(picLongitude-
mLongitude, picLatitude-mLatitude));
But when I use it on the updateDirection, the compass line stays
static.. doesn't moves just like it moved when the direction was 0
(north)
Do you have any ideia how can I implement this so that the
compass is
always pointing the picture position and not the north?
Thank you very much..if you didnt understood what I meant here,
basically I want a line that points me to an Latitude,Longitude
position other than the north itself.
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