1

2# -*- coding: utf-8 -*-

3

4 u'''I{Global Area Reference System} (GARS) en-/decoding.

5

6 Class L{Garef} and several functions to encode, decode and inspect

7 GARS references.

8

9 Transcoded from I{Charles Karney}'s C++ class U{GARS

10<https://GeographicLib.SourceForge.io/C++/doc/classGeographicLib_1_1GARS.html>}.

11

12@see: U{Global Area Reference System

13 <https://WikiPedia.org/wiki/Global_Area_Reference_System>} and U{NGA

14 (GARS)<https://Earth-Info.NGA.mil/GandG/coordsys/grids/gars.html>}.

15'''

16

17# from pygeodesy.basics import isstr # from .named

18 from pygeodesy.constants import _off90, _1_over, _0_5, \

19 _1_0 # PYCHOK used!

20 from pygeodesy.errors import _ValueError, _xkwds, _xStrError

21 from pygeodesy.interns import NN, _0to9_, _AtoZnoIO_, _COMMA_, \

22 _INV_, _SPACE_

23 from pygeodesy.lazily import _ALL_DOCS, _ALL_LAZY

24 from pygeodesy.named import _name__, Fmt, isstr, Property_RO

25 from pygeodesy.namedTuples import LatLon2Tuple, LatLonPrec3Tuple

26# from pygeodesy.props import Property_RO # from .named

27# from pygeodesy.streprs import Fmt # from .named

28 from pygeodesy.units import Int_, Lat, Lon, Precision_, Scalar_, Str

29

30 from math import floor

31

32__all__ = _ALL_LAZY.gars

33__version__ = '24.08.13'

34

35_Digits = _0to9_

36_LatLen = 2

37_LatOrig = -90

38_Letters = _AtoZnoIO_

39_LonLen = 3

40_LonOrig = -180

41_MaxPrec = 2

42

43_MinLen = _LonLen + _LatLen

44_MaxLen = _MinLen + _MaxPrec

45

46_M1 = _M2 = 2

47_M3 = 3

48_M4 = _M1 * _M2 * _M3

49

50_LatOrig_M4 = _LatOrig * _M4

51_LatOrig_M1 = _LatOrig * _M1

52_LonOrig_M4 = _LonOrig * _M4

53_LonOrig_M1_1 = _LonOrig * _M1 - 1

54

55_Resolutions = _1_over(_M1), _1_over(_M1 * _M2), _1_over(_M4)

56

57

58 def _2divmod2(ll, _Orig_M4):

59 x = int(floor(ll * _M4)) - _Orig_M4

60 i = (x * _M1) // _M4

61 x -= i * _M4 // _M1

62 return i, x

63

64

65 def _2fll(lat, lon, *unused):

66 '''(INTERNAL) Convert lat, lon.

67 '''

68 # lat, lon = parseDMS2(lat, lon)

69 return (Lat(lat, Error=GARSError),

70 Lon(lon, Error=GARSError))

71

72

73# def _2Garef(garef):

74# '''(INTERNAL) Check or create a L{Garef} instance.

75# '''

76# if not isinstance(garef, Garef):

77# try:

78# garef = Garef(garef)

79# except (TypeError, ValueError):

80# raise _xStrError(Garef, Str, garef=garef)

81# return garef

82

83

84 def _2garstr2(garef):

85 '''(INTERNAL) Check a garef string.

86 '''

87 try:

88 n, garstr = len(garef), garef.upper()

89 if n < _MinLen or n > _MaxLen \

90 or garstr.startswith(_INV_) \

91 or not garstr.isalnum():

92 raise ValueError()

93 return garstr, _2Precision(n - _MinLen)

94

95 except (AttributeError, TypeError, ValueError) as x:

96 raise GARSError(Garef.__name__, garef, cause=x)

97

98

99 def _2Precision(precision):

100 '''(INTERNAL) Return a L{Precision_} instance.

101 '''

102 return Precision_(precision, Error=GARSError, low=0, high=_MaxPrec)

103

104

105 class GARSError(_ValueError):

106 '''Global Area Reference System (GARS) encode, decode or other L{Garef} issue.

107 '''

108 pass

109

110

111 class Garef(Str):

112 '''Garef class, a named C{str}.

113 '''

114 # no str.__init__ in Python 3

115 def __new__(cls, lat_gll, lon=None, precision=1, **name):

116 '''New L{Garef} from an other L{Garef} instance or garef C{str}

117 or from a lat- and longitude.

118

119 @arg lat_gll: Latitude (C{degrees90}), a garef (L{Garef},

120 C{str}) or a location (C{LatLon}, C{LatLon*Tuple}).

121 @kwarg lon: Logitude (C{degrees180)}, required if B{C{lat_gll}}

122 is C{degrees90}, ignored otherwise.

123 @kwarg precision: The desired garef resolution and length (C{int}

124 0..2), see L{encode<pygeodesy.gars.encode>}.

125 @kwarg name: Optional C{B{name}=NN} (C{str}).

126

127 @return: New L{Garef}.

128

129 @raise GARSError: INValid B{C{lat_gll}}.

130

131 @raise RangeError: Invalid B{C{lat_gll}} or B{C{lon}}.

132

133 @raise TypeError: Invalid B{C{lat_gll}} or B{C{lon}}.

134 '''

135 if lon is None:

136 if isinstance(lat_gll, Garef):

137 g, ll, p = str(lat_gll), lat_gll.latlon, lat_gll.precision

138 elif isstr(lat_gll):

139 ll = lat_gll.replace(_COMMA_, _SPACE_).split()

140 if len(ll) > 1:

141 g, ll, p = _encode3(ll[0], ll[1], precision)

142 else:

143 g, ll = lat_gll.upper(), None

144 _, p = _2garstr2(g) # validate

145 else: # assume LatLon

146 try:

147 g, ll, p = _encode3(lat_gll.lat, lat_gll.lon, precision)

148 except AttributeError:

149 raise _xStrError(Garef, gll=lat_gll, Error=GARSError)

150 else:

151 g, ll, p = _encode3(lat_gll, lon, precision)

152

153 self = Str.__new__(cls, g, name=_name__(name, _or_nameof=lat_gll))

154 self._latlon = ll

155 self._precision = p

156 return self

157

158 @Property_RO

159 def decoded3(self):

160 '''Get this garef's attributes (L{LatLonPrec3Tuple}).

161 '''

162 lat, lon = self.latlon

163 return LatLonPrec3Tuple(lat, lon, self.precision, name=self.name)

164

165 @Property_RO

166 def _decoded3(self):

167 '''(INTERNAL) Initial L{LatLonPrec3Tuple}.

168 '''

169 return decode3(self)

170

171 @Property_RO

172 def latlon(self):

173 '''Get this garef's (center) lat- and longitude (L{LatLon2Tuple}).

174 '''

175 lat, lon = self._latlon or self._decoded3[:2]

176 return LatLon2Tuple(lat, lon, name=self.name)

177

178 @Property_RO

179 def precision(self):

180 '''Get this garef's precision (C{int}).

181 '''

182 p = self._precision

183 return self._decoded3.precision if p is None else p

184

185 def toLatLon(self, LatLon=None, **LatLon_kwds):

186 '''Return (the center of) this garef cell as an instance

187 of the supplied C{LatLon} class.

188

189 @kwarg LatLon: Class to use (C{LatLon} or C{None}).

190 @kwarg LatLon_kwds: Optional, additional B{C{LatLon}}

191 keyword arguments.

192

193 @return: This garef location as B{C{LatLon}} or if

194 C{B{LatLon} is None} as L{LatLonPrec3Tuple}.

195 '''

196 return self.decoded3 if LatLon is None else LatLon(

197 *self.latlon, **_xkwds(LatLon_kwds, name=self.name))

198

199

200 def decode3(garef, center=True, **name):

201 '''Decode a C{garef} to lat-, longitude and precision.

202

203 @arg garef: To be decoded (L{Garef} or C{str}).

204 @kwarg center: If C{True}, use the garef's center, otherwise

205 the south-west, lower-left corner (C{bool}).

206

207 @return: A L{LatLonPrec3Tuple}C{(lat, lon, precision)}.

208

209 @raise GARSError: Invalid B{C{garef}}, INValid, non-alphanumeric

210 or bad length B{C{garef}}.

211 '''

212 def _Error(i):

213 return GARSError(garef=Fmt.SQUARE(repr(garef), i))

214

215 def _ll(chars, g, i, j, lo, hi):

216 ll, b = 0, len(chars)

217 for i in range(i, j):

218 d = chars.find(g[i])

219 if d < 0:

220 raise _Error(i)

221 ll = ll * b + d

222 if ll < lo or ll > hi:

223 raise _Error(j)

224 return ll

225

226 def _ll2(lon, lat, g, i, m):

227 d = _Digits.find(g[i])

228 if d < 1 or d > m * m:

229 raise _Error(i)

230 d, r = divmod(d - 1, m)

231 lon = lon * m + r

232 lat = lat * m + (m - 1 - d)

233 return lon, lat

234

235 g, precision = _2garstr2(garef)

236

237 lon = _ll(_Digits, g, 0, _LonLen, 1, 720) + _LonOrig_M1_1

238 lat = _ll(_Letters, g, _LonLen, _MinLen, 0, 359) + _LatOrig_M1

239 if precision > 0:

240 lon, lat = _ll2(lon, lat, g, _MinLen, _M2)

241 if precision > 1:

242 lon, lat = _ll2(lon, lat, g, _MinLen + 1, _M3)

243

244 if center: # ll = (ll * 2 + 1) / 2

245 lon += _0_5

246 lat += _0_5

247

248 n = _name__(name, _or_nameof=garef)

249 r = _Resolutions[precision] # == 1.0 / unit

250 return LatLonPrec3Tuple(Lat(lat * r, Error=GARSError),

251 Lon(lon * r, Error=GARSError),

252 precision, name=n)

253

254

255 def encode(lat, lon, precision=1):

256 '''Encode a lat-/longitude as a C{garef} of the given precision.

257

258 @arg lat: Latitude (C{degrees}).

259 @arg lon: Longitude (C{degrees}).

260 @kwarg precision: Optional, the desired C{garef} resolution

261 and length (C{int} 0..2).

262

263 @return: The C{garef} (C{str}).

264

265 @raise RangeError: Invalid B{C{lat}} or B{C{lon}}.

266

267 @raise GARSError: Invalid B{C{precision}}.

268

269 @note: The C{garef} length is M{precision + 5} and the C{garef}

270 resolution is B{30′} for B{C{precision}} 0, B{15′} for 1

271 and B{5′} for 2, respectively.

272 '''

273 g, _, _ = _encode3(lat, lon, precision)

274 return g

275

276

277 def _encode3(lat, lon, precision): # MCCABE 14

278 '''Return 3-tuple C{(garef, (lat, lon), p)}.

279 '''

280 def _digit(x, y, m):

281 return _Digits[m * (m - y - 1) + x + 1],

282

283 def _str(chars, x, n):

284 s, b = [], len(chars)

285 for i in range(n):

286 x, i = divmod(x, b)

287 s.append(chars[i])

288 return tuple(reversed(s))

289

290 p = _2Precision(precision)

291

292 lat, lon = _2fll(lat, lon)

293

294 ix, x = _2divmod2( lon, _LonOrig_M4)

295 iy, y = _2divmod2(_off90(lat), _LatOrig_M4)

296

297 g = _str(_Digits, ix + 1, _LonLen) + \

298 _str(_Letters, iy, _LatLen)

299 if p > 0:

300 ix, x = divmod(x, _M3)

301 iy, y = divmod(y, _M3)

302 g += _digit(ix, iy, _M2)

303 if p > 1:

304 g += _digit(x, y, _M3)

305

306 return NN.join(g), (lat, lon), p

307

308

309 def precision(res):

310 '''Determine the L{Garef} precision to meet a required (geographic)

311 resolution.

312

313 @arg res: The required resolution (C{degrees}).

314

315 @return: The L{Garef} precision (C{int} 0..2).

316

317 @raise ValueError: Invalid B{C{res}}.

318

319 @see: Function L{gars.encode} for more C{precision} details.

320 '''

321 r = Scalar_(res=res)

322 for p in range(_MaxPrec):

323 if resolution(p) <= r:

324 return p

325 return _MaxPrec

326

327

328 def resolution(prec):

329 '''Determine the (geographic) resolution of a given L{Garef} precision.

330

331 @arg prec: The given precision (C{int}).

332

333 @return: The (geographic) resolution (C{degrees}).

334

335 @raise GARSError: Invalid B{C{prec}}.

336

337 @see: Function L{gars.encode} for more C{precision} details.

338 '''

339 p = Int_(prec=prec, Error=GARSError, low=-1, high=_MaxPrec + 1)

340 return _Resolutions[max(0, min(p, _MaxPrec))]

341

342

343__all__ += _ALL_DOCS(decode3, # functions

344 encode, precision, resolution)

345

346# **) MIT License

347#

348# Copyright (C) 2016-2025 -- mrJean1 at Gmail -- All Rights Reserved.

349#

350# Permission is hereby granted, free of charge, to any person obtaining a

351# copy of this software and associated documentation files (the "Software"),

352# to deal in the Software without restriction, including without limitation

353# the rights to use, copy, modify, merge, publish, distribute, sublicense,

354# and/or sell copies of the Software, and to permit persons to whom the

355# Software is furnished to do so, subject to the following conditions:

356#

357# The above copyright notice and this permission notice shall be included

358# in all copies or substantial portions of the Software.

359#

360# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS

361# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

362# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL

363# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR

364# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,

365# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR

366# OTHER DEALINGS IN THE SOFTWARE.