GeographicLib  1.52
GARS.cpp
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1 /**
2  * \file GARS.cpp
3  * \brief Implementation for GeographicLib::GARS class
4  *
5  * Copyright (c) Charles Karney (2015-2020) <charles@karney.com> and licensed
6  * under the MIT/X11 License. For more information, see
7  * https://geographiclib.sourceforge.io/
8  **********************************************************************/
9 
10 #include <GeographicLib/GARS.hpp>
12 
13 namespace GeographicLib {
14 
15  using namespace std;
16 
17  const char* const GARS::digits_ = "0123456789";
18  const char* const GARS::letters_ = "ABCDEFGHJKLMNPQRSTUVWXYZ";
19 
20  void GARS::Forward(real lat, real lon, int prec, string& gars) {
21  using std::isnan; // Needed for Centos 7, ubuntu 14
22  if (abs(lat) > 90)
23  throw GeographicErr("Latitude " + Utility::str(lat)
24  + "d not in [-90d, 90d]");
25  if (isnan(lat) || isnan(lon)) {
26  gars = "INVALID";
27  return;
28  }
29  lon = Math::AngNormalize(lon);
30  if (lon == 180) lon = -180; // lon now in [-180,180)
31  if (lat == 90) lat *= (1 - numeric_limits<real>::epsilon() / 2);
32  prec = max(0, min(int(maxprec_), prec));
33  int
34  x = int(floor(lon * m_)) - lonorig_ * m_,
35  y = int(floor(lat * m_)) - latorig_ * m_,
36  ilon = x * mult1_ / m_,
37  ilat = y * mult1_ / m_;
38  x -= ilon * m_ / mult1_; y -= ilat * m_ / mult1_;
39  char gars1[maxlen_];
40  ++ilon;
41  for (int c = lonlen_; c--;) {
42  gars1[c] = digits_[ ilon % baselon_]; ilon /= baselon_;
43  }
44  for (int c = latlen_; c--;) {
45  gars1[lonlen_ + c] = letters_[ilat % baselat_]; ilat /= baselat_;
46  }
47  if (prec > 0) {
48  ilon = x / mult3_; ilat = y / mult3_;
49  gars1[baselen_] = digits_[mult2_ * (mult2_ - 1 - ilat) + ilon + 1];
50  if (prec > 1) {
51  ilon = x % mult3_; ilat = y % mult3_;
52  gars1[baselen_ + 1] = digits_[mult3_ * (mult3_ - 1 - ilat) + ilon + 1];
53  }
54  }
55  gars.resize(baselen_ + prec);
56  copy(gars1, gars1 + baselen_ + prec, gars.begin());
57  }
58 
59  void GARS::Reverse(const string& gars, real& lat, real& lon,
60  int& prec, bool centerp) {
61  int len = int(gars.length());
62  if (len >= 3 &&
63  toupper(gars[0]) == 'I' &&
64  toupper(gars[1]) == 'N' &&
65  toupper(gars[2]) == 'V') {
66  lat = lon = Math::NaN();
67  return;
68  }
69  if (len < baselen_)
70  throw GeographicErr("GARS must have at least 5 characters " + gars);
71  if (len > maxlen_)
72  throw GeographicErr("GARS can have at most 7 characters " + gars);
73  int prec1 = len - baselen_;
74  int ilon = 0;
75  for (int c = 0; c < lonlen_; ++c) {
76  int k = Utility::lookup(digits_, gars[c]);
77  if (k < 0)
78  throw GeographicErr("GARS must start with 3 digits " + gars);
79  ilon = ilon * baselon_ + k;
80  }
81  if (!(ilon >= 1 && ilon <= 720))
82  throw GeographicErr("Initial digits in GARS must lie in [1, 720] " +
83  gars);
84  --ilon;
85  int ilat = 0;
86  for (int c = 0; c < latlen_; ++c) {
87  int k = Utility::lookup(letters_, gars[lonlen_ + c]);
88  if (k < 0)
89  throw GeographicErr("Illegal letters in GARS " + gars.substr(3,2));
90  ilat = ilat * baselat_ + k;
91  }
92  if (!(ilat < 360))
93  throw GeographicErr("GARS letters must lie in [AA, QZ] " + gars);
94  real
95  unit = mult1_,
96  lat1 = ilat + latorig_ * unit,
97  lon1 = ilon + lonorig_ * unit;
98  if (prec1 > 0) {
99  int k = Utility::lookup(digits_, gars[baselen_]);
100  if (!(k >= 1 && k <= mult2_ * mult2_))
101  throw GeographicErr("6th character in GARS must [1, 4] " + gars);
102  --k;
103  unit *= mult2_;
104  lat1 = mult2_ * lat1 + (mult2_ - 1 - k / mult2_);
105  lon1 = mult2_ * lon1 + (k % mult2_);
106  if (prec1 > 1) {
107  k = Utility::lookup(digits_, gars[baselen_ + 1]);
108  if (!(k >= 1 /* && k <= mult3_ * mult3_ */))
109  throw GeographicErr("7th character in GARS must [1, 9] " + gars);
110  --k;
111  unit *= mult3_;
112  lat1 = mult3_ * lat1 + (mult3_ - 1 - k / mult3_);
113  lon1 = mult3_ * lon1 + (k % mult3_);
114  }
115  }
116  if (centerp) {
117  unit *= 2; lat1 = 2 * lat1 + 1; lon1 = 2 * lon1 + 1;
118  }
119  lat = lat1 / unit;
120  lon = lon1 / unit;
121  prec = prec1;
122  }
123 
124 } // namespace GeographicLib
Header for GeographicLib::GARS class.
Header for GeographicLib::Utility class.
static void Reverse(const std::string &gars, real &lat, real &lon, int &prec, bool centerp=true)
Definition: GARS.cpp:59
static void Forward(real lat, real lon, int prec, std::string &gars)
Definition: GARS.cpp:20
Exception handling for GeographicLib.
Definition: Constants.hpp:315
static T AngNormalize(T x)
Definition: Math.hpp:420
static T NaN()
Definition: Math.cpp:260
static int lookup(const std::string &s, char c)
Definition: Utility.hpp:461
static std::string str(T x, int p=-1)
Definition: Utility.hpp:276
Namespace for GeographicLib.
Definition: Accumulator.cpp:12