GeographicLib 2.3

GARS.cpp
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1/**
2 * \file GARS.cpp
3 * \brief Implementation for GeographicLib::GARS class
4 *
5 * Copyright (c) Charles Karney (2015-2022) <karney@alum.mit.edu> and licensed
6 * under the MIT/X11 License. For more information, see
7 * https://geographiclib.sourceforge.io/
8 **********************************************************************/
9
10#include <GeographicLib/GARS.hpp>
11#include <GeographicLib/Utility.hpp>
12
13#if defined(_MSC_VER)
14// Squelch warnings about enum-float expressions
15# pragma warning (disable: 5055)
16#endif
17
18 namespace GeographicLib {
19
20 using namespace std;
21
22 const char* const GARS::digits_ = "0123456789";
23 const char* const GARS::letters_ = "ABCDEFGHJKLMNPQRSTUVWXYZ";
24
25 void GARS::Forward(real lat, real lon, int prec, string& gars) {
26 using std::isnan; // Needed for Centos 7, ubuntu 14
27 if (fabs(lat) > Math::qd)
28 throw GeographicErr("Latitude " + Utility::str(lat)
29 + "d not in [-" + to_string(Math::qd)
30 + "d, " + to_string(Math::qd) + "d]");
31 if (isnan(lat) || isnan(lon)) {
32 gars = "INVALID";
33 return;
34 }
35 lon = Math::AngNormalize(lon);
36 if (lon == Math::hd) lon = -Math::hd; // lon now in [-180,180)
37 if (lat == Math::qd) lat *= (1 - numeric_limits<real>::epsilon() / 2);
38 prec = max(0, min(int(maxprec_), prec));
39 int
40 x = int(floor(lon * m_)) - lonorig_ * m_,
41 y = int(floor(lat * m_)) - latorig_ * m_,
42 ilon = x * mult1_ / m_,
43 ilat = y * mult1_ / m_;
44 x -= ilon * m_ / mult1_; y -= ilat * m_ / mult1_;
45 char gars1[maxlen_];
46 ++ilon;
47 for (int c = lonlen_; c--;) {
48 gars1[c] = digits_[ ilon % baselon_]; ilon /= baselon_;
49 }
50 for (int c = latlen_; c--;) {
51 gars1[lonlen_ + c] = letters_[ilat % baselat_]; ilat /= baselat_;
52 }
53 if (prec > 0) {
54 ilon = x / mult3_; ilat = y / mult3_;
55 gars1[baselen_] = digits_[mult2_ * (mult2_ - 1 - ilat) + ilon + 1];
56 if (prec > 1) {
57 ilon = x % mult3_; ilat = y % mult3_;
58 gars1[baselen_ + 1] = digits_[mult3_ * (mult3_ - 1 - ilat) + ilon + 1];
59 }
60 }
61 gars.resize(baselen_ + prec);
62 copy(gars1, gars1 + baselen_ + prec, gars.begin());
63 }
64
65 void GARS::Reverse(const string& gars, real& lat, real& lon,
66 int& prec, bool centerp) {
67 int len = int(gars.length());
68 if (len >= 3 &&
69 toupper(gars[0]) == 'I' &&
70 toupper(gars[1]) == 'N' &&
71 toupper(gars[2]) == 'V') {
72 lat = lon = Math::NaN();
73 return;
74 }
75 if (len < baselen_)
76 throw GeographicErr("GARS must have at least 5 characters " + gars);
77 if (len > maxlen_)
78 throw GeographicErr("GARS can have at most 7 characters " + gars);
79 int prec1 = len - baselen_;
80 int ilon = 0;
81 for (int c = 0; c < lonlen_; ++c) {
82 int k = Utility::lookup(digits_, gars[c]);
83 if (k < 0)
84 throw GeographicErr("GARS must start with 3 digits " + gars);
85 ilon = ilon * baselon_ + k;
86 }
87 if (!(ilon >= 1 && ilon <= 2 * Math::td))
88 throw GeographicErr("Initial digits in GARS must lie in [1, 720] " +
89 gars);
90 --ilon;
91 int ilat = 0;
92 for (int c = 0; c < latlen_; ++c) {
93 int k = Utility::lookup(letters_, gars[lonlen_ + c]);
94 if (k < 0)
95 throw GeographicErr("Illegal letters in GARS " + gars.substr(3,2));
96 ilat = ilat * baselat_ + k;
97 }
98 if (!(ilat < Math::td))
99 throw GeographicErr("GARS letters must lie in [AA, QZ] " + gars);
100 real
101 unit = mult1_,
102 lat1 = ilat + latorig_ * unit,
103 lon1 = ilon + lonorig_ * unit;
104 if (prec1 > 0) {
105 int k = Utility::lookup(digits_, gars[baselen_]);
106 if (!(k >= 1 && k <= mult2_ * mult2_))
107 throw GeographicErr("6th character in GARS must [1, 4] " + gars);
108 --k;
109 unit *= mult2_;
110 lat1 = mult2_ * lat1 + (mult2_ - 1 - k / mult2_);
111 lon1 = mult2_ * lon1 + (k % mult2_);
112 if (prec1 > 1) {
113 k = Utility::lookup(digits_, gars[baselen_ + 1]);
114 if (!(k >= 1 /* && k <= mult3_ * mult3_ */))
115 throw GeographicErr("7th character in GARS must [1, 9] " + gars);
116 --k;
117 unit *= mult3_;
118 lat1 = mult3_ * lat1 + (mult3_ - 1 - k / mult3_);
119 lon1 = mult3_ * lon1 + (k % mult3_);
120 }
121 }
122 if (centerp) {
123 unit *= 2; lat1 = 2 * lat1 + 1; lon1 = 2 * lon1 + 1;
124 }
125 lat = lat1 / unit;
126 lon = lon1 / unit;
127 prec = prec1;
128 }
129
130} // namespace GeographicLib
GARS.hpp
Header for GeographicLib::GARS class.
Utility.hpp
Header for GeographicLib::Utility class.
GeographicLib::GARS::Reverse
static void Reverse(const std::string &gars, real &lat, real &lon, int &prec, bool centerp=true)
Definition: GARS.cpp:65
GeographicLib::GARS::Forward
static void Forward(real lat, real lon, int prec, std::string &gars)
Definition: GARS.cpp:25
GeographicLib::GeographicErr
Exception handling for GeographicLib.
Definition: Constants.hpp:316
GeographicLib::Math::AngNormalize
static T AngNormalize(T x)
Definition: Math.cpp:71
GeographicLib::Math::NaN
static T NaN()
Definition: Math.cpp:250
GeographicLib::Math::td
@ td
degrees per turn
Definition: Math.hpp:142
GeographicLib::Math::hd
@ hd
degrees per half turn
Definition: Math.hpp:141
GeographicLib::Math::qd
@ qd
degrees per quarter turn
Definition: Math.hpp:138
GeographicLib::Utility::lookup
static int lookup(const std::string &s, char c)
Definition: Utility.cpp:160
GeographicLib::Utility::str
static std::string str(T x, int p=-1)
Definition: Utility.hpp:161
GeographicLib
Namespace for GeographicLib.
Definition: Accumulator.cpp:12
std
Definition: NearestNeighbor.hpp:812