Function MGRStoLatLon

libs/platform/utm_mgrs_utils.cpp:397–434

Convert MGRS parameters to UTM parameters and then use UTM to lat,lon conversion.

// Convert MGRS parameters to UTM parameters and then use UTM to lat,lon conversion.
std::optional<ms::LatLon> MGRStoLatLon(int easting, int northing, int zoneCode, char zoneLetter, char squareCode[2])
{
  // Convert easting and northing according to zone_code and square_code
  if (zoneCode < 1 || zoneCode > 60)
    return {};

  if (zoneLetter <= 'B' || zoneLetter >= 'Y' || zoneLetter == 'I' || zoneLetter == 'O')
    return {};

  int const set = zoneCode % kSetOriginColumnLetters.size();

  auto const char1 = squareCode[0];
  auto const char2 = squareCode[1];

  if (char1 < 'A' || char2 < 'A' || char1 > 'Z' || char2 > 'Z' || char1 == 'I' || char2 == 'I' || char1 == 'O' ||
      char2 == 'O')
    return {};

  int const east100k = SquareCharToEasting(char1, set);
  if (east100k == kInvalidEastingNorthing)
    return {};

  int north100k = SquareCharToNorthing(char2, set);
  if (north100k == kInvalidEastingNorthing)
    return {};

  int const minNorthing = ZoneToMinNorthing(zoneLetter);
  if (minNorthing == kInvalidEastingNorthing)
    return {};

  while (north100k < minNorthing)
    north100k += 2000000;

  easting += east100k;
  northing += north100k;

  return UTMtoLatLon(easting, northing, zoneCode, zoneLetter);
}

// Convert lat,lon for WGS84 ellipsoid to MGRS string.
std::string FormatMGRS(double lat, double lon, int precision)