nmea.cpp

#include "nmea.hpp"
#include "wgs84point.hpp"
#include <boost/date_time/gregorian/gregorian.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>
#include <boost/format.hpp>
#include <cassert>
#include <cmath>
#include <iomanip>
#include <sstream>
 
namespace vanetza
{
namespace nmea
{
 
using namespace vanetza::units;
 
/**
 * Print latitude data in BBBB.BBBB, b format.
 * BBBB.BBBB are degrees and minutes (ddmm.mm)
 * b is N or S
 */
void print_latitude(std::ostream& os, const Wgs84Point& point)
{
    double degrees = point.lat.value();
    double minutes = std::modf(std::abs(degrees), &degrees) * 60.0;
    os << boost::format("%02d%07.4f") % degrees % minutes;
    os << "," << (point.lat.value() >= 0.0 ? "N" : "S");
}
 
/**
 * Print longitude data in LLLL.LLLL, l format.
 * LLLL.LLLL are degrees and minutes (ddmm.mm)
 * l is E or W
 */
void print_longitude(std::ostream& os, const Wgs84Point& point)
{
    double degrees = point.lon.value();
    double minutes = std::modf(std::abs(degrees), &degrees) * 60.0;
    os << boost::format("%02d%07.4f") % degrees % minutes;
    os << "," << (point.lon.value() >= 0.0 ? "E" : "W");
}
 
namespace detail
{
 
struct latitude
{
    latitude(const Wgs84Point& p) : point(p) {}
    friend std::ostream& operator<<(std::ostream& os, const latitude& lat)
    {
        print_latitude(os, lat.point);
        return os;
    }
 
    const Wgs84Point& point;
};
 
struct longitude
{
    longitude(const Wgs84Point& p) : point(p) {}
    friend std::ostream& operator<<(std::ostream& os, const longitude& lon)
    {
        print_longitude(os, lon.point);
        return os;
    }
 
    const Wgs84Point& point;
};
 
} // namespace detail
 
detail::latitude latitude(const Wgs84Point& p) { return detail::latitude(p); }
detail::longitude longitude(const Wgs84Point& p) { return detail::longitude(p); }
 
/**
 * Finish NMEA sentence with *XX where XX is the calculated checksum
 * \param smsg NMEA sentence with leading $ but without trailing *XX
 * \return finished NMEA sentence
 */
std::string finish(std::stringstream& smsg)
{
    std::string msg = smsg.str();
    unsigned sum = checksum(++msg.begin(), msg.end());
    msg += boost::str(boost::format("*%02X") % static_cast<unsigned>(sum));
    return msg;
}
 
std::string gprmc(const time& ptime, const Wgs84Point& wgs84,
        NauticalVelocity ground_speed, TrueNorth heading)
{
    /**
     * Magnetic declination for central europe is about 1 degree east (2010), see this map for reference:
     * http://upload.wikimedia.org/wikipedia/commons/d/dd/World_Magnetic_Model_Main_Field_Declination_D_2010.png
     */
    const double magnetic_angle = 1.0;
    const char magnetic_direction = 'E';
 
    std::stringstream smsg;
    smsg << std::uppercase << std::fixed;
    auto* tfacet = new boost::posix_time::time_facet("%H%M%S");
    auto* dfacet = new boost::gregorian::date_facet("%d%m%y");
    smsg.imbue(std::locale(smsg.getloc(), tfacet));
    smsg.imbue(std::locale(smsg.getloc(), dfacet));
 
    smsg << "$GPRMC,";
    smsg << ptime << ","; // HHMMSS
    smsg << static_cast<char>(RMCStatus::Valid) << ",";
    smsg << latitude(wgs84) << "," << longitude(wgs84) << ",";
    smsg << std::setprecision(1) << ground_speed.value() << ","; // GG.G
    smsg << std::setprecision(1) << std::fmod(heading.value(), 360.0) << ","; // RR.R
    smsg << ptime.date() << ","; // DDMMYY
    smsg << std::setprecision(1) << magnetic_angle << "," << magnetic_direction << ","; // M.M, E/W
    smsg << static_cast<char>(FAAMode::Autonomous);
 
    return finish(smsg);
}
 
std::string gpgga(const time& ptime, const Wgs84Point& wgs84, Quality quality, Length hdop)
{
    const unsigned satellites = 6; // Arbitrary number of used GPS satellites
    const double height = 0.0; // SUMO map is flat
    const double separation = 0.0; // Geoidal separation, can it be calculated?
 
    std::stringstream smsg;
    smsg << std::uppercase << std::fixed;
    auto* facet = new boost::posix_time::time_facet("%H%M%s");
    smsg.imbue(std::locale(smsg.getloc(), facet));
 
    smsg << "$GPGGA,";
    smsg << ptime << ","; // HHMMSS.ss
    smsg << latitude(wgs84) << "," << longitude(wgs84) << ",";
    smsg << static_cast<std::underlying_type<Quality>::type>(quality) << ","; // Q
    smsg << std::setw(2) << std::setfill('0') << satellites << ","; // NN
    smsg << std::setprecision(1) << hdop.value() << ","; // D.D
    smsg << std::setprecision(1) << height << ",M,"; // H.H, h
    smsg << std::setprecision(1) << separation << ",M,"; // G.G, g
    smsg << ","; // AA, RRRR (both optional)
 
    return finish(smsg);
}
 
uint8_t checksum(std::string::const_iterator begin, std::string::const_iterator end)
{
    assert(begin <= end);
    uint8_t sum = 0;
    for (; begin != end; ++begin) {
        sum ^= *begin;
    }
    return sum;
}
 
} // namespace nmea
} // namespace vanetza