File content as of revision 5:94daced1e61a:

#include "GPS_parser.h"

GPS_Parser::GPS_Parser()
{
    nmea_longitude = 0.0;
    nmea_latitude = 0.0;
    utc_time = 0;
    ns = ' ';
    ew = ' ';
    lock = 0;
    satelites = 0;
    hdop = 0.0;
    msl_altitude = 0.0;
    msl_units = ' ';

    rmc_status = ' ';
    speed_k = 0.0;
    course_d = 0.0;
    date = 0;

    dec_longitude = 0.0;
    dec_latitude = 0.0;

    gll_status = ' ';

    course_t = 0.0; // ground speed true
    course_t_unit = ' ';
    course_m = 0.0; // magnetic
    course_m_unit = ' ';
    speed_k_unit = ' ';
    speed_km = 0.0; // speek km/hr
    speed_km_unit = ' ';

    altitude_ft = 0.0;
}

float GPS_Parser::nmea_to_dec(float deg_coord, char nsew)
{
    int degree = (int)(deg_coord/100);
    float minutes = deg_coord - degree*100;
    float dec_deg = minutes / 60;
    float decimal = degree + dec_deg;
    if (nsew == 'S' || nsew == 'W') { // return negative
        decimal *= -1;
    }
    return decimal;
}

int GPS_Parser::sample(char *msg)
{
    int line_parsed = 0;

    // Check if it is a GPGGA msg (matches both locked and non-locked msg)
    if (sscanf(msg, "$GPGGA,%f,%f,%c,%f,%c,%d,%d,%f,%f,%c", &utc_time, &nmea_latitude, &ns, &nmea_longitude, &ew, &lock, &satelites, &hdop, &msl_altitude, &msl_units) >= 1) {
        line_parsed = GGA;
    }
    // Check if it is a GPRMC msg
    else if (sscanf(msg, "$GPRMC,%f,%f,%c,%f,%c,%f,%f,%d", &utc_time, &nmea_latitude, &ns, &nmea_longitude, &ew, &speed_k, &course_d, &date) >= 1) {
        line_parsed = RMC;
    }

    if(satelites == 0) {
        lock = 0;
    }
    if (!lock) {
        return NO_LOCK;
    } else if (line_parsed) {
        return line_parsed;
    } else {
        return NOT_PARSED;
    }
}


// INTERNAL FUNCTINS ////////////////////////////////////////////////////////////
float GPS_Parser::trunc(float v)
{
    if (v < 0.0) {
        v*= -1.0;
        v = floor(v);
        v*=-1.0;
    } else {
        v = floor(v);
    }
    return v;
}

// GET FUNCTIONS /////////////////////////////////////////////////////////////////
float GPS_Parser::get_msl_altitude()
{
    if (!lock)
        return 0.0;
    else
        return msl_altitude;
}

int GPS_Parser::get_satelites()
{
    if (!lock)
        return 0;
    else
        return satelites;
}

float GPS_Parser::get_nmea_longitude()
{
    if (!lock)
        return 0.0;
    else
        return nmea_longitude;
}

float GPS_Parser::get_dec_longitude()
{
    dec_longitude = nmea_to_dec(nmea_longitude, ew);
    if (!lock)
        return 0.0;
    else
        return dec_longitude;
}

float GPS_Parser::get_nmea_latitude()
{
    if (!lock)
        return 0.0;
    else
        return nmea_latitude;
}

float GPS_Parser::get_dec_latitude()
{
    dec_latitude = nmea_to_dec(nmea_latitude, ns);
    if (!lock)
        return 0.0;
    else
        return dec_latitude;
}

float GPS_Parser::get_course_t()
{
    if (!lock)
        return 0.0;
    else
        return course_t;
}

float GPS_Parser::get_course_m()
{
    if (!lock)
        return 0.0;
    else
        return course_m;
}

float GPS_Parser::get_speed_k()
{
    if (!lock)
        return 0.0;
    else
        return speed_k;
}

float GPS_Parser::get_speed_km()
{
    if (!lock)
        return 0.0;
    else
        return speed_km;
}

float GPS_Parser::get_altitude_ft()
{
    if (!lock)
        return 0.0;
    else
        return 3.280839895*msl_altitude;
}

// NAVIGATION FUNCTIONS ////////////////////////////////////////////////////////////
float GPS_Parser::calc_course_to(float pointLat, float pontLong)
{
    const double d2r = PI / 180.0;
    const double r2d = 180.0 / PI;
    double dlat = abs(pointLat - get_dec_latitude()) * d2r;
    double dlong = abs(pontLong - get_dec_longitude()) * d2r;
    double y = sin(dlong) * cos(pointLat * d2r);
    double x = cos(get_dec_latitude()*d2r)*sin(pointLat*d2r) - sin(get_dec_latitude()*d2r)*cos(pointLat*d2r)*cos(dlong);
    return 360.0-(atan2(y,x)*r2d);
}

/*
var y = Math.sin(dLon) * Math.cos(lat2);
var x = Math.cos(lat1)*Math.sin(lat2) -
        Math.sin(lat1)*Math.cos(lat2)*Math.cos(dLon);
var brng = Math.atan2(y, x).toDeg();
*/

/*
            The Haversine formula according to Dr. Math.
            http://mathforum.org/library/drmath/view/51879.html

            dlon = lon2 - lon1
            dlat = lat2 - lat1
            a = (sin(dlat/2))^2 + cos(lat1) * cos(lat2) * (sin(dlon/2))^2
            c = 2 * atan2(sqrt(a), sqrt(1-a))
            d = R * c

            Where
                * dlon is the change in longitude
                * dlat is the change in latitude
                * c is the great circle distance in Radians.
                * R is the radius of a spherical Earth.
                * The locations of the two points in
                    spherical coordinates (longitude and
                    latitude) are lon1,lat1 and lon2, lat2.
*/
double GPS_Parser::calc_dist_to_mi(float pointLat, float pontLong)
{
    const double d2r = PI / 180.0;
    double dlat = pointLat - get_dec_latitude();
    double dlong = pontLong - get_dec_longitude();
    double a = pow(sin(dlat/2.0),2.0) + cos(get_dec_latitude()*d2r) * cos(pointLat*d2r) * pow(sin(dlong/2.0),2.0);
    double c = 2.0 * asin(sqrt(abs(a)));
    double d = 63.765 * c;

    return d;
}

double GPS_Parser::calc_dist_to_ft(float pointLat, float pontLong)
{
    return calc_dist_to_mi(pointLat, pontLong)*5280.0;
}

double GPS_Parser::calc_dist_to_km(float pointLat, float pontLong)
{
    return calc_dist_to_mi(pointLat, pontLong)*1.609344;
}

double GPS_Parser::calc_dist_to_m(float pointLat, float pontLong)
{
    return calc_dist_to_mi(pointLat, pontLong)*1609.344;
}