GARS.hpp

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#if !defined(GEOGRAPHICLIB_GARS_HPP)
#define GEOGRAPHICLIB_GARS_HPP 1

#include <GeographicLib/Constants.hpp>

#if defined(_MSC_VER)
// Squelch warnings about dll vs string
#  pragma warning (push)
#  pragma warning (disable: 4251)
#endif

namespace GeographicLib {

  class GEOGRAPHICLIB_EXPORT GARS {
  private:
    typedef Math::real real;
    static const char* const digits_;
    static const char* const letters_;
    enum {
      lonorig_ = -180,          // Origin for longitude
      latorig_ = -90,           // Origin for latitude
      baselon_ = 10,            // Base for longitude tiles
      baselat_ = 24,            // Base for latitude tiles
      lonlen_ = 3,
      latlen_ = 2,
      baselen_ = lonlen_ + latlen_,
      mult1_ = 2,               // base precision = 1/2 degree
      mult2_ = 2,               // 6th char gives 2x more precision
      mult3_ = 3,               // 7th char gives 3x more precision
      m_ = mult1_ * mult2_ * mult3_,
      maxprec_ = 2,
      maxlen_ = baselen_ + maxprec_,
    };
    GARS();                     // Disable constructor

  public:

    static void Forward(real lat, real lon, int prec, std::string& gars);

    static void Reverse(const std::string& gars, real& lat, real& lon,
                        int& prec, bool centerp = true);

    static Math::real Resolution(int prec) {
      return 1/real(prec <= 0 ? mult1_ : (prec == 1 ? mult1_ * mult2_ :
                                          mult1_ * mult2_ * mult3_));
    }

    static int Precision(real res) {
      using std::abs; res = abs(res);
      for (int prec = 0; prec < maxprec_; ++prec)
        if (Resolution(prec) <= res)
          return prec;
      return maxprec_;
    }

  };

} // namespace GeographicLib

#if defined(_MSC_VER)
#  pragma warning (pop)
#endif

#endif  // GEOGRAPHICLIB_GARS_HPP