[EricS-Team180]

You might try splitting things up, temporarily to get to the bottom of it...

int nav_heading;
int new_pos;
int old_pos;
int dist=0;
int nav_x;
int nav_y;

void Navigation(void)
{
	
float temp ;

	nav_heading = Get_Gyro_Angle();
	
	new_pos = (int)( Get_Left_Encoder_Count() + Get_Right_Encoder_Count() )/2;  
	

	dist = (new_pos - old_pos);

        /*nav_x+= (int) cos((float) nav_heading /1000) * dist;*/
        /* ...add printfs to keep checking the value of temp*/ 
         temp = (float) nav_heading ;
         temp /= 1000. ;
         temp = cos(temp) ; 
         temp *= (float)dist ;
	 nav_x = (int)temp ;

	nav_y+= (int) sin((float)nav_heading/1000) * dist;

	
	old_pos = new_pos;
}

That always helps me figure out casting peculiarities...

Eric