zr-v4/libraries/AP_Math/location.cpp

/*
 * location.cpp
 * Copyright (C) Andrew Tridgell 2011
 *
 * This file is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This file is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *  this module deals with calculations involving struct Location
 */
#include <AP_HAL/AP_HAL.h>
#include <stdlib.h>
#include "AP_Math.h"
#include "location.h"
#include "AP_Common/Location.h"

// return horizontal distance between two positions in cm
float get_horizontal_distance_cm(const Vector3f &origin, const Vector3f &destination)
{
    return norm(destination.x-origin.x,destination.y-origin.y);
}

// return bearing in centi-degrees between two locations
int32_t get_bearing_cd(const struct Location &loc1, const struct Location &loc2)
{
    int32_t off_x = loc2.lng - loc1.lng;
    const int32_t off_y = (loc2.lat - loc1.lat) / loc2.longitude_scale();
    int32_t bearing = 9000 + atan2f(-off_y, off_x) * DEGX100;
    if (bearing < 0) bearing += 36000;
    return bearing;
}

// return bearing in centi-degrees between two positions
float get_bearing_cd(const Vector3f &origin, const Vector3f &destination)
{
    float bearing = atan2f(destination.y-origin.y, destination.x-origin.x) * DEGX100;
    if (bearing < 0) {
        bearing += 36000.0f;
    }
    return bearing;
}

// see if location is past a line perpendicular to
// the line between point1 and point2. If point1 is
// our previous waypoint and point2 is our target waypoint
// then this function returns true if we have flown past
// the target waypoint
bool location_passed_point(const struct Location &location,
                           const struct Location &point1,
                           const struct Location &point2)
{
    return location_path_proportion(location, point1, point2) >= 1.0f;
}


/*
  return the proportion we are along the path from point1 to
  point2, along a line parallel to point1<->point2.

  This will be less than >1 if we have passed point2
 */
float location_path_proportion(const struct Location &location,
                               const struct Location &point1,
                               const struct Location &point2)
{
    Vector2f vec1 = location_diff(point1, point2);
    Vector2f vec2 = location_diff(point1, location);
    float dsquared = sq(vec1.x) + sq(vec1.y);
    if (dsquared < 0.001f) {
        // the two points are very close together
        return 1.0f;
    }
    return (vec1 * vec2) / dsquared;
}

/*
 *  extrapolate latitude/longitude given bearing and distance
 * Note that this function is accurate to about 1mm at a distance of 
 * 100m. This function has the advantage that it works in relative
 * positions, so it keeps the accuracy even when dealing with small
 * distances and floating point numbers
 */
void location_update(struct Location &loc, float bearing, float distance)
{
    float ofs_north = cosf(radians(bearing))*distance;
    float ofs_east  = sinf(radians(bearing))*distance;
    loc.offset(ofs_north, ofs_east);
}

/*
  return the distance in meters in North/East plane as a N/E vector
  from loc1 to loc2
 */
Vector2f location_diff(const struct Location &loc1, const struct Location &loc2)
{
    return Vector2f((loc2.lat - loc1.lat) * LOCATION_SCALING_FACTOR,
                    (loc2.lng - loc1.lng) * LOCATION_SCALING_FACTOR * loc1.longitude_scale());
}

/*
  return the distance in meters in North/East/Down plane as a N/E/D vector
  from loc1 to loc2
 */
Vector3f location_3d_diff_NED(const struct Location &loc1, const struct Location &loc2)
{
    return Vector3f((loc2.lat - loc1.lat) * LOCATION_SCALING_FACTOR,
                    (loc2.lng - loc1.lng) * LOCATION_SCALING_FACTOR * loc1.longitude_scale(),
                    (loc1.alt - loc2.alt) * 0.01f);
}

/*
  return true if lat and lng match. Ignores altitude and options
 */
bool locations_are_same(const struct Location &loc1, const struct Location &loc2) {
    return (loc1.lat == loc2.lat) && (loc1.lng == loc2.lng);
}

// return true when lat and lng are within range
bool check_lat(float lat)
{
    return fabsf(lat) <= 90;
}
bool check_lng(float lng)
{
    return fabsf(lng) <= 180;
}
bool check_lat(int32_t lat)
{
    return labs(lat) <= 90*1e7;
}
bool check_lng(int32_t lng)
{
    return labs(lng) <= 180*1e7;
}
bool check_latlng(float lat, float lng)
{
    return check_lat(lat) && check_lng(lng);
}
bool check_latlng(int32_t lat, int32_t lng)
{
    return check_lat(lat) && check_lng(lng);
}
bool check_latlng(Location loc)
{
    return check_lat(loc.lat) && check_lng(loc.lng);
}