Function LatLonToUtm

libs/platform/utm_mgrs_utils.cpp:101–144

Main algorithm. Formulas source: https://github.com/Turbo87/utm

// Main algorithm. Formulas source: https://github.com/Turbo87/utm
UTMPoint LatLonToUtm(double lat, double lon)
{
  using std::sin, std::cos, std::sqrt;

  double const latRad = math::DegToRad(lat);
  double const latSin = sin(latRad);
  double const latCos = cos(latRad);

  double const latTan = latSin / latCos;
  double const latTan2 = latTan * latTan;
  double const latTan4 = latTan2 * latTan2;

  int const zoneNumber = LatLonToZoneNumber(lat, lon);
  auto const zoneLetter = LatitudeToZoneLetter(lat);
  ASSERT(zoneLetter, (lat));

  double const lonRad = math::DegToRad(lon);
  double const centralLon = ZoneNumberToCentralLon(zoneNumber);
  double const centralLonRad = math::DegToRad(centralLon);

  double const n = R / sqrt(1.0 - E * latSin * latSin);
  double const c = E_P2 * latCos * latCos;

  double const a = latCos * NormalizeAngle(lonRad - centralLonRad);
  double const a2 = a * a;
  double const a3 = a2 * a;
  double const a4 = a3 * a;
  double const a5 = a4 * a;
  double const a6 = a5 * a;

  double const m = R * (M1 * latRad - M2 * sin(2 * latRad) + M3 * sin(4 * latRad) - M4 * sin(6 * latRad));

  double const easting =
      K0 * n * (a + a3 / 6 * (1 - latTan2 + c) + a5 / 120 * (5 - 18 * latTan2 + latTan4 + 72 * c - 58 * E_P2)) +
      500000.0;

  double northing = K0 * (m + n * latTan *
                                  (a2 / 2 + a4 / 24 * (5 - latTan2 + 9 * c + 4 * c * c) +
                                   a6 / 720 * (61 - 58 * latTan2 + latTan4 + 600 * c - 330 * E_P2)));
  if (lat < 0.0)
    northing += 10000000.0;

  return {easting, northing, zoneNumber, zoneLetter};
}

// Generate UTM string from UTM point parameters.
std::string UTMtoStr(UTMPoint const & point)