Add functions for computation of the distance and bearing to the nearest point of a line segment or arc segment.

apps/systemlib/geo/geo.c

@@ -68,10 +68,10 @@ __EXPORT float get_distance_to_next_waypoint(double lat_now, double lon_now, dou
 
 __EXPORT float get_bearing_to_next_waypoint(double lat_now, double lon_now, double lat_next, double lon_next)
 {
-	double lat_now_rad = lat_now / 180.0 * M_PI;
-	double lon_now_rad = lon_now / 180.0 * M_PI;
-	double lat_next_rad = lat_next / 180.0 * M_PI;
-	double lon_next_rad = lon_next / 180.0 * M_PI;
+	double lat_now_rad = lat_now * M_DEG_TO_RAD;
+	double lon_now_rad = lon_now * M_DEG_TO_RAD;
+	double lat_next_rad = lat_next * M_DEG_TO_RAD;
+	double lon_next_rad = lon_next * M_DEG_TO_RAD;
 
 	double d_lat = lat_next_rad - lat_now_rad;
 	double d_lon = lon_next_rad - lon_now_rad;
@@ -79,13 +79,195 @@ __EXPORT float get_bearing_to_next_waypoint(double lat_now, double lon_now, doub
 	/* conscious mix of double and float trig function to maximize speed and efficiency */
 	float theta = atan2f(sin(d_lon) * cos(lat_next_rad) , cos(lat_now_rad) * sin(lat_next_rad) - sin(lat_now_rad) * cos(lat_next_rad) * cos(d_lon));
 
-	if (theta < M_PI_F) {
-		theta += 2.0f * M_PI_F;
-	}
-
-	if (theta > M_PI_F) {
-		theta -= 2.0f * M_PI_F;
-	}
+	theta = _wrapPI(theta);
 
 	return theta;
-}
+}
+
+// Additional functions - @author Doug Weibel <douglas.weibel@colorado.edu>
+
+__EXPORT crosstrack_error_s get_distance_to_line(double lat_now, double lon_now, double lat_start, double lon_start, double lat_end, double lon_end)
+{
+// This function returns the distance to the nearest point on the track line.  Distance is positive if current
+// position is right of the track and negative if left of the track as seen from a point on the track line 
+// headed towards the end point.
+
+	crosstrack_error_s return_var;
+	float dist_to_end;
+	float bearing_end;
+	float bearing_track;
+	float bearing_diff;
+	
+	return_var.error = true;		// Set error flag, cleared when valid result calculated.
+	return_var.past_end = false;
+	return_var.distance = 0.0f;
+	return_var.bearing = 0.0f;
+	
+	// Return error if arguments are bad
+	if(lat_now == 0.0d || lon_now == 0.0d || lat_start == 0.0d || lon_start == 0.0d || lat_end == 0.0d || lon_end == 0.0d) return return_var;
+	
+	bearing_end = get_bearing_to_next_waypoint(lat_now, lon_now, lat_end, lon_end);
+	bearing_track = get_bearing_to_next_waypoint(lat_start, lon_start, lat_end, lon_end);
+	bearing_diff = bearing_track - bearing_end;
+	bearing_diff = _wrapPI(bearing_diff);
+	
+	// Return past_end = true if past end point of line
+	if(bearing_diff > M_PI_2_F || bearing_diff < -M_PI_2_F) {
+		return_var.past_end = true;
+		return_var.error = false;
+		return return_var;
+	}
+	
+	dist_to_end = get_distance_to_next_waypoint(lat_now, lon_now, lat_end, lon_end);
+	return_var.distance = (dist_to_end)*sin(bearing_diff);
+	if(sin(bearing_diff) >=0 ) {
+		return_var.bearing = _wrapPI(bearing_track - M_PI_2_F);
+	} else {
+		return_var.bearing = _wrapPI(bearing_track + M_PI_2_F);
+	}
+	return_var.error = false;
+	
+	return return_var;
+
+}
+
+
+__EXPORT crosstrack_error_s get_distance_to_arc(double lat_now, double lon_now, double lat_center, double lon_center, 
+									float radius, float arc_start_bearing, float arc_sweep)
+{
+	// This function returns the distance to the nearest point on the track arc.  Distance is positive if current
+	// position is right of the arc and negative if left of the arc as seen from the closest point on the arc and
+	// headed towards the end point.
+	crosstrack_error_s return_var;
+
+	// Determine if the current position is inside or outside the sector between the line from the center
+	// to the arc start and the line from the center to the arc end
+	float	bearing_sector_start;
+	float	bearing_sector_end;
+	float	bearing_now = get_bearing_to_next_waypoint(lat_now, lon_now, lat_center, lon_center);
+	bool	in_sector;
+	
+	return_var.error = true;		// Set error flag, cleared when valid result calculated.
+	return_var.past_end = false;
+	return_var.distance = 0.0f;
+	return_var.bearing = 0.0f;
+	
+	// Return error if arguments are bad
+	if(lat_now == 0.0d || lon_now == 0.0d || lat_center == 0.0d || lon_center == 0.0d || radius == 0.0d) return return_var;
+	
+	
+	if(arc_sweep >= 0) {
+		bearing_sector_start = arc_start_bearing;
+		bearing_sector_end = arc_start_bearing + arc_sweep;
+		if(bearing_sector_end > 2.0f*M_PI_F) bearing_sector_end -= M_TWOPI_F;
+	} else {
+		bearing_sector_end = arc_start_bearing;
+		bearing_sector_start = arc_start_bearing - arc_sweep;
+		if(bearing_sector_start < 0.0) bearing_sector_start += M_TWOPI_F;
+	}
+	in_sector = false;
+	
+	// Case where sector does not span zero
+	if(bearing_sector_end >= bearing_sector_start && bearing_now >= bearing_sector_start && bearing_now <= bearing_sector_end) in_sector = true;
+	
+	// Case where sector does span zero
+	if(bearing_sector_end < bearing_sector_start && ( bearing_now > bearing_sector_start || bearing_now < bearing_sector_end ) ) in_sector = true;
+	
+	// If in the sector then calculate distance and bearing to closest point
+	if(in_sector) {
+		return_var.past_end = false;
+		float dist_to_center = get_distance_to_next_waypoint(lat_now, lon_now, lat_center, lon_center);
+		
+		if(dist_to_center <= radius) {
+			return_var.distance = radius - dist_to_center;
+			return_var.bearing = bearing_now + M_PI_F;
+		} else {
+			return_var.distance = dist_to_center - radius;
+			return_var.bearing = bearing_now;
+		}
+		
+	// If out of the sector then calculate dist and bearing to start or end point
+	} else {
+	
+	// Use the approximation  that 111,111 meters in the y direction is 1 degree (of latitude) 
+	// and 111,111 * cos(latitude) meters in the x direction is 1 degree (of longitude) to
+	// calculate the position of the start and end points.  We should not be doing this often
+	// as this function generally will not be called repeatedly when we are out of the sector.
+	
+	// TO DO - this is messed up and won't compile
+		float start_disp_x = radius * sin(arc_start_bearing);
+		float start_disp_y = radius * cos(arc_start_bearing);
+		float end_disp_x = radius * sin(_wrapPI(arc_start_bearing+arc_sweep));
+		float end_disp_y = radius * cos(_wrapPI(arc_start_bearing+arc_sweep));
+		float lon_start = lon_now + start_disp_x/111111.0d;
+		float lat_start = lat_now + start_disp_y*cos(lat_now)/111111.0d;
+		float lon_end = lon_now + end_disp_x/111111.0d;
+		float lat_end = lat_now + end_disp_y*cos(lat_now)/111111.0d;
+		float dist_to_start = get_distance_to_next_waypoint(lat_now, lon_now, lat_start, lon_start);
+		float dist_to_end = get_distance_to_next_waypoint(lat_now, lon_now, lat_end, lon_end);
+		if(dist_to_start < dist_to_end) {
+			return_var.distance = dist_to_start;
+			return_var.bearing = get_bearing_to_next_waypoint(lat_now, lon_now, lat_start, lon_start);
+		} else {
+			return_var.past_end = true;
+			return_var.distance = dist_to_end;
+			return_var.bearing = get_bearing_to_next_waypoint(lat_now, lon_now, lat_end, lon_end);
+		}
+
+	}
+	
+	return_var.bearing = _wrapPI(return_var.bearing);
+	return_var.error = false;
+	return return_var;	
+}
+
+float _wrapPI(float bearing)
+{
+
+	while (bearing > M_PI_F) {
+		bearing = bearing - M_TWOPI_F;
+	}
+	while (bearing <=  -M_PI_F) {
+		bearing = bearing + M_TWOPI_F;
+	}
+	return bearing;
+}
+		
+float _wrap2PI(float bearing)
+{
+
+	while (bearing >= M_TWOPI_F) {
+		bearing = bearing - M_TWOPI_F;
+	}
+	while (bearing <  0.0f) {
+		bearing = bearing + M_TWOPI_F;
+	}
+	return bearing;
+}
+
+float _wrap180(float bearing)
+{
+
+	while (bearing > 180.0f) {
+		bearing = bearing - 360.0f;
+	}
+	while (bearing <=  -180.0f) {
+		bearing = bearing + 360.0f;
+	}
+	return bearing;
+}
+		
+float _wrap360(float bearing)
+{
+
+	while (bearing >= 360.0f) {
+		bearing = bearing - 360.0f;
+	}
+	while (bearing <  0.0f) {
+		bearing = bearing + 360.0f;
+	}
+	return bearing;
+}
+		
+
+	

apps/systemlib/geo/geo.h

@@ -42,8 +42,31 @@
  * @author Thomas Gubler <thomasgubler@student.ethz.ch>
  * @author Julian Oes <joes@student.ethz.ch>
  * @author Lorenz Meier <lm@inf.ethz.ch>
+ * Additional functions - @author Doug Weibel <douglas.weibel@colorado.edu>
  */
+ 
+ 
+#include <stdbool.h>
+
+typedef struct {
+	bool error;			// Flag that the calculation failed
+	bool past_end;		// Flag indicating we are past the end of the line/arc segment
+	float distance;		// Distance in meters to closest point on line/arc
+	float bearing;		// Bearing in radians to closest point on line/arc
+} crosstrack_error_s;
 
 __EXPORT float get_distance_to_next_waypoint(double lat_now, double lon_now, double lat_next, double lon_next);
 
 __EXPORT float get_bearing_to_next_waypoint(double lat_now, double lon_now, double lat_next, double lon_next);
+
+// 
+
+__EXPORT crosstrack_error_s get_distance_to_line(double lat_now, double lon_now, double lat_start, double lon_start, double lat_end, double lon_end);
+
+__EXPORT crosstrack_error_s get_distance_to_arc(double lat_now, double lon_now, double lat_center, double lon_center, 
+									 float radius, float arc_start_bearing, float arc_sweep);
+									 
+float _wrap180(float bearing);
+float _wrap360(float bearing);	 
+float _wrapPI(float bearing);
+float _wrap2PI(float bearing);

nuttx/arch/arm/include/math.h

@@ -544,6 +544,8 @@ extern int matherr _PARAMS((struct exception *e));
 #define M_1_PI		0.31830988618379067154
 #define M_2_PI		0.63661977236758134308
 #define M_2_SQRTPI	1.12837916709551257390
+#define M_DEG_TO_RAD 	0.01745329251994
+#define M_RAD_TO_DEG 	57.2957795130823
 #define M_SQRT2		1.41421356237309504880
 #define M_SQRT1_2	0.70710678118654752440
 #define M_LN2LO         1.9082149292705877000E-10
@@ -568,6 +570,8 @@ extern int matherr _PARAMS((struct exception *e));
 #define M_1_PI_F		0.31830988618379067154f
 #define M_2_PI_F		0.63661977236758134308f
 #define M_2_SQRTPI_F	1.12837916709551257390f
+#define M_DEG_TO_RAD_F 	0.01745329251994f
+#define M_RAD_TO_DEG_F 	57.2957795130823f
 #define M_SQRT2_F		1.41421356237309504880f
 #define M_SQRT1_2_F		0.70710678118654752440f
 #define M_LN2LO_F       1.9082149292705877000E-10f