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# -*- coding: utf-8 -*- 

 

u'''Classes L{Geohash} and L{GeohashError} and several functions to 

encode, decode and inspect I{geohashes}. 

 

Transcribed from JavaScript originals by I{(C) Chris Veness 2011-2015} 

and published under the same MIT Licence**, see U{Geohashes 

<https://www.Movable-Type.co.UK/scripts/geohash.html>}. 

 

See also U{Geohash<https://WikiPedia.org/wiki/Geohash>}, 

U{Geohash<https://GitHub.com/vinsci/geohash>}, 

U{PyGeohash<https://PyPI.org/project/pygeohash>} and 

U{Geohash-Javascript<https://GitHub.com/DaveTroy/geohash-js>}. 

 

@newfield example: Example, Examples 

''' 

 

from pygeodesy.basics import isstr, map2, property_RO, _xkwds 

from pygeodesy.dms import parse3llh # parseDMS2 

from pygeodesy.errors import _ValueError 

from pygeodesy.fmath import favg 

from pygeodesy.formy import equirectangular, equirectangular_, haversine_ 

from pygeodesy.interns import EPS, NN, R_M, _E_, _N_, _NE_, _NW_, _S_, \ 

_SE_, _SW_, _W_, _0_5, _90_0, _180_0, _360_0 

from pygeodesy.lazily import _ALL_DOCS, _ALL_LAZY, _ALL_OTHER 

from pygeodesy.named import _NamedDict 

from pygeodesy.namedTuples import Bounds2Tuple, Bounds4Tuple, LatLon2Tuple 

from pygeodesy.streprs import fstr 

from pygeodesy.units import Int, Lat, Lon, Precision_, Radius, \ 

Scalar_, Str, _xStrError 

from pygeodesy.utily import unrollPI 

 

from math import ldexp, log10, radians 

 

__all__ = _ALL_LAZY.geohash 

__version__ = '20.10.02' 

 

_Border = dict( 

N=('prxz', 'bcfguvyz'), 

S=('028b', '0145hjnp'), 

E=('bcfguvyz', 'prxz'), 

W=('0145hjnp', '028b')) 

 

_Bounds4 = -_90_0, -_180_0, _90_0, _180_0 

_MaxPrec = 12 

 

_Neighbor = dict( 

N=('p0r21436x8zb9dcf5h7kjnmqesgutwvy', 'bc01fg45238967deuvhjyznpkmstqrwx'), 

S=('14365h7k9dcfesgujnmqp0r2twvyx8zb', '238967debc01fg45kmstqrwxuvhjyznp'), 

E=('bc01fg45238967deuvhjyznpkmstqrwx', 'p0r21436x8zb9dcf5h7kjnmqesgutwvy'), 

W=('238967debc01fg45kmstqrwxuvhjyznp', '14365h7k9dcfesgujnmqp0r2twvyx8zb')) 

 

# lat-, longitudinal and radial cell size (in meter) 

_Sizes = ( # radius = sqrt(latHeight * lonWidth / PI) 

(20032e3, 20000e3, 11292815.096), # 0 

( 5003e3, 5000e3, 2821794.075), # 1 

( 650e3, 1225e3, 503442.397), # 2 

( 156e3, 156e3, 88013.575), # 3 

( 19500, 39100, 15578.683), # 4 

( 4890, 4890, 2758.887), # 5 

( 610, 1220, 486.710), # 6 

( 153, 153, 86.321), # 7 

( 19.1, 38.2, 15.239), # 8 

( 4.77, 4.77, 2.691), # 9 

( 0.596, 1.19, 0.475), # 10 

( 0.149, 0.149, 0.084), # 11 

( 0.0186, 0.0372, 0.015)) # 12 _MaxPrec 

 

# Geohash-specific base32 map 

_GeohashBase32 = '0123456789bcdefghjkmnpqrstuvwxyz' # no a, i, j and o 

# ... and the inverse map 

_DecodedBase32 = dict((c, i) for i, c in enumerate(_GeohashBase32)) 

c = i = None 

del c, i 

 

 

def _2bounds(LatLon, LatLon_kwds, s, w, n, e): 

'''(INTERNAL) Return SW and NE bounds. 

''' 

return Bounds4Tuple(s, w, n, e) if LatLon is None else ( 

Bounds2Tuple(LatLon(s, w, **LatLon_kwds), 

LatLon(n, e, **LatLon_kwds))) # PYCHOK inconsistent 

 

 

def _2center(bounds): 

'''(INTERNAL) Return the C{bounds} center. 

''' 

return (favg(bounds.latN, bounds.latS), 

favg(bounds.lonE, bounds.lonW)) 

 

 

def _2fll(lat, lon, *unused): 

'''(INTERNAL) Convert lat, lon to 2-tuple of floats. 

''' 

# lat, lon = parseDMS2(lat, lon) 

return (Lat(lat, Error=GeohashError), 

Lon(lon, Error=GeohashError)) 

 

 

def _2Geohash(geohash): 

'''(INTERNAL) Check or create a Geohash instance. 

''' 

return geohash if isinstance(geohash, Geohash) else \ 

Geohash(geohash) 

 

 

def _2geostr(geohash): 

'''(INTERNAL) Check a geohash string. 

''' 

try: 

if not (0 < len(geohash) <= _MaxPrec): 

raise ValueError 

geostr = geohash.lower() 

for c in geostr: 

if c not in _DecodedBase32: 

raise ValueError 

return geostr 

except (AttributeError, TypeError, ValueError) as x: 

raise GeohashError(Geohash.__name__, geohash, txt=str(x)) 

 

 

class Geohash(Str): 

'''Geohash class, a named C{str}. 

''' 

_bounds = None # cached bounds property 

_latlon = None # cached latlon property 

 

_N = None # cached neighbors properties 

_E = None 

_S = None 

_W = None 

 

# no str.__init__ in Python 3 

def __new__(cls, cll, precision=None, name=NN): 

'''New L{Geohash} from an other L{Geohash} instance or C{str} 

or from a C{LatLon} instance or C{str}. 

 

@arg cll: Cell or location (L{Geohash} or C{str}, C{LatLon} 

or C{str}). 

@kwarg precision: Optional, the desired geohash length (C{int} 

1..12), see function L{geohash.encode} for 

some examples. 

@kwarg name: Optional name (C{str}). 

 

@return: New L{Geohash}. 

 

@raise TypeError: Invalid B{C{cll}}. 

 

@raise GeohashError: INValid or non-alphanumeric B{C{cll}}. 

''' 

if isinstance(cll, Geohash): 

gh = _2geostr(str(cll)) 

self = Str.__new__(cls, gh) 

 

elif isstr(cll): 

if ',' in cll: 

lat, lon = _2fll(*parse3llh(cll)) 

gh = encode(lat, lon, precision=precision) 

self = Str.__new__(cls, gh) 

self._latlon = lat, lon 

else: 

gh = _2geostr(cll) 

self = Str.__new__(cls, gh) 

 

else: # assume LatLon 

try: 

lat, lon = _2fll(cll.lat, cll.lon) 

except AttributeError: 

raise _xStrError(Geohash, cll=cll) # Error=GeohashError 

gh = encode(lat, lon, precision=precision) 

self = Str.__new__(cls, gh) 

self._latlon = lat, lon 

 

if name: 

self.name = name 

return self 

 

@property_RO 

def ab(self): 

'''Get the lat- and longitude of (the approximate center of) 

this geohash as a 2-tuple (lat, lon) in C{radians}. 

''' 

return map2(radians, self.latlon) 

 

def adjacent(self, direction): 

'''Determine the adjacent cell in given compass direction. 

 

@arg direction: Compass direction ('N', 'S', 'E' or 'W'). 

 

@return: Geohash of adjacent cell (L{Geohash}). 

 

@raise GeohashError: Invalid geohash or B{C{direction}}. 

''' 

# based on <https://GitHub.com/DaveTroy/geohash-js> 

 

d = direction[:1].upper() 

if d not in _Neighbor: 

raise GeohashError(direction=direction) 

 

e = len(self) & 1 # % 2 

 

c = self[-1:] # last hash char 

i = _Neighbor[d][e].find(c) 

if i < 0: 

raise GeohashError(geohash=self) 

 

p = self[:-1] # hash without last char 

# check for edge-cases which don't share common prefix 

if p and (c in _Border[d][e]): 

p = Geohash(p).adjacent(d) 

 

# append letter for direction to parent 

return Geohash(p + _GeohashBase32[i]) 

 

def bounds(self, LatLon=None, **LatLon_kwds): 

'''Return the lower-left SW and upper-right NE bounds of this 

geohash cell. 

 

@kwarg LatLon: Optional class to return I{bounds} (C{LatLon}) 

or C{None}. 

@kwarg LatLon_kwds: Optional keyword arguments for B{{LatLon}}. 

 

@return: A L{Bounds2Tuple}C{(latlonSW, latlonNE)} of B{C{LatLon}}s 

or if B{C{LatLon}} is C{None}, a L{Bounds4Tuple}C{(latS, 

lonW, latN, lonE)}. 

''' 

if not self._bounds: 

self._bounds = bounds(self) 

return _2bounds(LatLon, LatLon_kwds, *self._bounds) 

 

def distance1(self, other): # PYCHOK no cover 

'''DEPRECATED, use method C{distance1To}. 

''' 

return self.distance1To(other) 

 

def distance1To(self, other): 

'''Estimate the distance between this and an other geohash 

(from the cell sizes). 

 

@arg other: The other geohash (L{Geohash}). 

 

@return: Approximate distance (C{meter}). 

 

@raise TypeError: The B{C{other}} is not a L{Geohash}, 

C{LatLon} or C{str}. 

''' 

other = _2Geohash(other) 

 

n = min(len(self), len(other), len(_Sizes)) 

for n in range(n): 

if self[n] != other[n]: 

break 

return float(_Sizes[n][2]) 

 

def distance2(self, other, radius=R_M, adjust=False, wrap=False): # PYCHOK no cover 

'''DEPRECATED, use method C{distance2To}. 

''' 

return self.distance2To(other, radius=radius, adjust=adjust, wrap=wrap) 

 

def distance2To(self, other, radius=R_M, adjust=False, wrap=False): 

'''Compute the distance between this and an other geohash 

using the U{Equirectangular Approximation / Projection 

<https://www.Movable-Type.co.UK/scripts/latlong.html>}. 

 

@arg other: The other geohash (L{Geohash}). 

@kwarg radius: Mean earth radius (C{meter}) or C{None}. 

@kwarg adjust: Adjust the wrapped, unrolled longitudinal 

delta by the cosine of the mean latitude 

C{bool}). 

@kwarg wrap: Wrap and unroll longitudes (C{bool}). 

 

@return: Approximate distance (C{meter}, same units as I{radius}) 

or distance squared (C{degrees squared}) if I{radius} 

is C{None} or 0. 

 

@raise TypeError: The I{other} is not a L{Geohash}, C{LatLon} 

or C{str}. 

 

@see: U{Local, flat earth approximation 

<https://www.EdWilliams.org/avform.htm#flat>}, functions 

''' 

other = _2Geohash(other) 

 

a1, b1 = self.latlon 

a2, b2 = other.latlon 

if radius: 

return equirectangular(a1, b1, a2, b2, radius=radius, 

adjust=adjust, limit=None, wrap=wrap) 

else: 

return equirectangular_(a1, b1, a2, b2, 

adjust=adjust, limit=None, wrap=wrap)[0] 

 

def distance3(self, other, radius=R_M, wrap=False): # PYCHOK no cover 

'''DEPRECATED, use method C{distance3To}. 

''' 

return self.distance3To(other, radius=radius, wrap=wrap) 

 

def distance3To(self, other, radius=R_M, wrap=False): 

'''Compute the great-circle distance between this and an other 

geohash using the U{Haversine 

<https://www.Movable-Type.co.UK/scripts/latlong.html>} formula. 

 

@arg other: The other geohash (L{Geohash}). 

@kwarg radius: Mean earth radius (C{meter}). 

@kwarg wrap: Wrap and unroll longitudes (C{bool}). 

 

@return: Great-circle distance (C{meter}, same units as I{radius}). 

 

@raise TypeError: The I{other} is not a L{Geohash}, C{LatLon} 

or C{str}. 

 

@raise ValueError: Invalid B{C{radius}}. 

''' 

other = _2Geohash(other) 

 

a1, b1 = self.ab 

a2, b2 = other.ab 

 

db, _ = unrollPI(b1, b2, wrap=wrap) 

return haversine_(a2, a1, db) * Radius(radius) 

 

@property_RO 

def latlon(self): 

'''Get the lat- and longitude of (the approximate center of) 

this geohash as a L{LatLon2Tuple}C{(lat, lon)} in C{degrees}. 

 

B{Example:} 

 

>>> geohash.Geohash('geek').latlon # 65.478515625, -17.75390625 

>>> geohash.decode('geek') # '65.48', '-17.75' 

''' 

# B{Example:} not @example: since that causes Epydoc error 

if not self._latlon: 

lat, lon = _2center(self.bounds()) 

self._latlon = LatLon2Tuple(lat, lon) 

return self._latlon 

 

@property_RO 

def neighbors(self): 

'''Get all 8 adjacent cells as a L{Neighbors8Dict}C{(N, NE, 

E, SE, S, SW, W, NW)} of L{Geohash}es. 

 

B{JSname:} I{neighbours}. 

''' 

r = Neighbors8Dict(N=self.N, NE=self.NE, E=self.E, SE=self.SE, 

S=self.S, SW=self.SW, W=self.W, NW=self.NW) 

return self._xnamed(r) 

 

@property_RO 

def precision(self): 

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

''' 

return len(self) 

 

@property_RO 

def sizes(self): 

'''Get the lat- and longitudinal size of this cell as 

a L{LatLon2Tuple}C{(lat, lon)} with the latitudinal 

height and longitudinal width in (C{meter}). 

''' 

n = min(len(_Sizes) - 1, self.precision or 1) 

return LatLon2Tuple(*map2(float, _Sizes[n][:2])) # XXX Height, Width 

 

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

'''Return (the approximate center of) this geohash cell 

as an instance of the supplied C{LatLon} class. 

 

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

@kwarg LatLon_kwds: Optional keyword arguments for B{C{LatLon}}, 

ignored if C{B{LatLon}=None}. 

 

@return: This geohash location (B{C{LatLon}}). 

 

@raise TypeError: Invalid B{C{LatLon}} or B{C{LatLon_kwds}}. 

 

@example: 

 

>>> from sphericalTrigonometry import LatLon 

>>> ll = Geohash('u120fxw').toLatLon(LatLon) 

>>> print(repr(ll)) # LatLon(52°12′17.9″N, 000°07′07.64″E) 

>>> print(ll) # 52.204971°N, 000.11879°E 

''' 

r = self.latlon 

if LatLon: 

r = LatLon(*r, **LatLon_kwds) 

return self._xnamed(r) 

 

@property_RO 

def N(self): 

'''Get the cell North of this (L{Geohash}). 

''' 

if self._N is None: 

self._N = self.adjacent(_N_) 

return self._N 

 

@property_RO 

def S(self): 

'''Get the cell South of this (L{Geohash}). 

''' 

if self._S is None: 

self._S = self.adjacent(_S_) 

return self._S 

 

@property_RO 

def E(self): 

'''Get the cell East of this (L{Geohash}). 

''' 

if self._E is None: 

self._E = self.adjacent(_E_) 

return self._E 

 

@property_RO 

def W(self): 

'''Get the cell West of this (L{Geohash}). 

''' 

if self._W is None: 

self._W = self.adjacent(_W_) 

return self._W 

 

@property_RO 

def NE(self): 

'''Get the cell NorthEast of this (L{Geohash}). 

''' 

return self.N.E 

 

@property_RO 

def NW(self): 

'''Get the cell NorthWest of this (L{Geohash}). 

''' 

return self.N.W 

 

@property_RO 

def SE(self): 

'''Get the cell SouthEast of this (L{Geohash}). 

''' 

return self.S.E 

 

@property_RO 

def SW(self): 

'''Get the cell SouthWest of this (L{Geohash}). 

''' 

return self.S.W 

 

 

class GeohashError(_ValueError): 

'''Geohash encode, decode or other L{Geohash} issue. 

''' 

pass 

 

 

class Neighbors8Dict(_NamedDict): # replacing Neighbors8Dict 

'''8-Dict C{(N, NE, E, SE, S, SW, W, NW)} of L{Geohash}es, 

providing key I{and} attribute access to the items. 

''' 

_Keys_ = (_N_, _NE_, _E_, _SE_, _S_, _SW_, _W_, _NW_) 

 

def __init__(self, **kwds): # PYCHOK no *args 

kwds = _xkwds(kwds, **_Neighbors8Defaults) 

_NamedDict.__init__(self, **kwds) # name=... 

 

 

_Neighbors8Defaults = dict(zip(Neighbors8Dict._Keys_, (None,) * 

len(Neighbors8Dict._Keys_))) # XXX frozendict 

 

 

def bounds(geohash, LatLon=None, **LatLon_kwds): 

'''Returns the lower-left SW and upper-right NE corners of a geohash. 

 

@arg geohash: To be bound (L{Geohash}). 

@kwarg LatLon: Optional class to return the bounds (C{LatLon}) 

or C{None}. 

@kwarg LatLon_kwds: Optional keyword arguments for B{C{LatLon}}. 

 

@return: A L{Bounds2Tuple}C{(latlonSW, latlonNE)} of B{C{LatLon}}s 

or if B{C{LatLon}} is C{None}, a L{Bounds4Tuple}C{(latS, 

lonW, latN, lonE)}. 

 

@raise TypeError: The B{C{geohash}} is not a L{Geohash}, C{LatLon} 

or C{str} or invalid B{C{LatLon}} or invalid 

B{C{LatLon_kwds}}. 

 

@raise GeohashError: Invalid or C{null} B{C{geohash}}. 

 

@example: 

 

>>> geohash.bounds('u120fxw') # 52.20428467, 0.11810303, 

# 52.20565796, 0.11947632 

>>> geohash.decode('u120fxw') # '52.205', '0.1188' 

''' 

gh = _2Geohash(geohash) 

if len(gh) < 1: 

raise GeohashError(geohash=geohash) 

 

s, w, n, e = _Bounds4 

 

d = True 

for c in gh: # .lower(): 

try: 

i = _DecodedBase32[c] 

except KeyError: 

raise GeohashError(geohash=geohash) 

 

for m in (16, 8, 4, 2, 1): 

if d: # longitude 

if i & m: 

w = favg(w, e) 

else: 

e = favg(w, e) 

else: # latitude 

if i & m: 

s = favg(s, n) 

else: 

n = favg(s, n) 

d = not d 

 

return _2bounds(LatLon, LatLon_kwds, s, w, n, e) 

 

 

def decode(geohash): 

'''Decode a geohash to lat-/longitude of the (approximate 

centre of) geohash cell, to reasonable precision. 

 

@arg geohash: To be decoded (L{Geohash}). 

 

@return: 2-Tuple C{"(latStr, lonStr)"} in (C{str}). 

 

@raise TypeError: The B{C{geohash}} is not a L{Geohash}, 

C{LatLon} or C{str}. 

 

@raise GeohashError: Invalid or null B{C{geohash}}. 

 

@example: 

 

>>> geohash.decode('u120fxw') # '52.205', '0.1188' 

>>> geohash.decode('sunny') # '23.708', '42.473' Saudi Arabia 

>>> geohash.decode('fur') # '69.6', '-45.7' Greenland 

>>> geohash.decode('reef') # '-24.87', '162.95' Coral Sea 

>>> geohash.decode('geek') # '65.48', '-17.75' Iceland 

''' 

b = bounds(geohash) 

lat, lon = _2center(b) 

 

# round to near centre without excessive precision 

# ⌊2-log10(Δ°)⌋ decimal places, strip trailing zeros 

return (fstr(lat, prec=int(2 - log10(b.latN - b.latS))), 

fstr(lon, prec=int(2 - log10(b.lonE - b.lonW)))) # strings 

 

 

def decode_error(geohash): 

'''Return the relative lat-/longitude decoding errors for 

this geohash. 

 

@arg geohash: To be decoded (L{Geohash}). 

 

@return: A L{LatLon2Tuple}C{(lat, lon)} with the lat- and 

longitudinal errors in (C{degrees}). 

 

@raise TypeError: The B{C{geohash}} is not a L{Geohash}, 

C{LatLon} or C{str}. 

 

@raise GeohashError: Invalid or null B{C{geohash}}. 

 

@example: 

 

>>> geohash.decode_error('u120fxw') # 0.00068665, 0.00068665 

>>> geohash.decode_error('fur') # 0.703125, 0.703125 

>>> geohash.decode_error('fu') # 2.8125, 5.625 

>>> geohash.decode_error('f') # 22.5, 22.5 

''' 

b = bounds(geohash) 

return LatLon2Tuple((b.latN - b.latS) * _0_5, # Height 

(b.lonE - b.lonW) * _0_5) # Width 

 

 

def distance1(geohash1, geohash2): 

'''Estimate the distance between two geohash (from the cell sizes). 

 

@arg geohash1: First geohash (L{Geohash}). 

@arg geohash2: Second geohash (L{Geohash}). 

 

@return: Approximate distance (C{meter}). 

 

@raise TypeError: If B{C{geohash1}} or B{C{geohash2}} is not a 

L{Geohash}, C{LatLon} or C{str}. 

 

@example: 

 

>>> geohash.distance1('u120fxwsh', 'u120fxws0') # 15.239 

''' 

return _2Geohash(geohash1).distance1(geohash2) 

 

 

def distance2(geohash1, geohash2, radius=R_M): 

'''Approximate the distance between two geohashes (with 

Pythagoras' theorem). 

 

@arg geohash1: First geohash (L{Geohash}). 

@arg geohash2: Second geohash (L{Geohash}). 

@kwarg radius: Mean earth radius (C{meter}) or C{None}. 

 

@return: Approximate distance (C{meter}, same units as B{C{radius}}). 

 

@raise TypeError: If B{C{geohash1}} or B{C{geohash2}} is not a 

L{Geohash}, C{LatLon} or C{str}. 

 

@example: 

 

>>> geohash.distance2('u120fxwsh', 'u120fxws0') # 19.0879 

''' 

return _2Geohash(geohash1).distance2(geohash2, radius=radius) 

 

 

def distance3(geohash1, geohash2, radius=R_M): 

'''Compute the great-circle distance between two geohashes 

(using the Haversine formula). 

 

@arg geohash1: First geohash (L{Geohash}). 

@arg geohash2: Second geohash (L{Geohash}). 

@kwarg radius: Mean earth radius (C{meter}). 

 

@return: Great-circle distance (C{meter}, same units as B{C{radius}}). 

 

@raise TypeError: If B{C{geohash1}} or B{C{geohash2}} is not a 

L{Geohash}, C{LatLon} or C{str}. 

 

@example: 

 

>>> geohash.distance3('u120fxwsh', 'u120fxws0') # 11.6978 

''' 

return _2Geohash(geohash1).distance3(geohash2, radius=radius) 

 

 

def encode(lat, lon, precision=None): 

'''Encode a lat-/longitude as a C{geohash}, either to the specified 

precision or if not provided, to an automatically evaluated 

precision. 

 

@arg lat: Latitude (C{degrees}). 

@arg lon: Longitude (C{degrees}). 

@kwarg precision: Optional, the desired geohash length (C{int} 

1..12). 

 

@return: The C{geohash} (C{str}). 

 

@raise GeohashError: Invalid B{C{lat}}, B{C{lon}} or B{C{precision}}. 

 

@example: 

 

>>> geohash.encode(52.205, 0.119, 7) # 'u120fxw' 

>>> geohash.encode(52.205, 0.119, 12) # 'u120fxwshvkg' 

>>> geohash.encode(52.205, 0.1188, 12) # 'u120fxws0jre' 

>>> geohash.encode(52.205, 0.1188) # 'u120fxw' 

>>> geohash.encode( 0, 0) # 's00000000000' 

''' 

lat, lon = _2fll(lat, lon) 

 

if precision is None: 

# Infer precision by refining geohash until 

# it matches precision of supplied lat/lon. 

for p in range(1, _MaxPrec + 1): 

gh = encode(lat, lon, p) 

ll = map2(float, decode(gh)) 

if abs(lat - ll[0]) < EPS and \ 

abs(lon - ll[1]) < EPS: 

return gh 

p = _MaxPrec 

else: 

p = Precision_(precision, Error=GeohashError, low=1, high=_MaxPrec) 

 

s, w, n, e = _Bounds4 

 

b = i = 0 

d, gh = True, [] 

 

while len(gh) < p: 

i += i 

if d: # bisect longitude 

m = favg(e, w) 

if lon < m: 

e = m 

else: 

w = m 

i += 1 

else: # bisect latitude 

m = favg(n, s) 

if lat < m: 

n = m 

else: 

s = m 

i += 1 

d = not d 

 

b += 1 

if b == 5: 

# 5 bits gives a character: 

# append it and start over 

gh.append(_GeohashBase32[i]) 

b = i = 0 

 

return NN.join(gh) 

 

 

def neighbors(geohash): 

'''Return the L{Geohash}es for all 8 adjacent cells. 

 

@arg geohash: Cell for which neighbors are requested 

(L{Geohash} or C{str}). 

 

@return: A L{Neighbors8Dict}C{(N, NE, E, SE, S, SW, W, NW)} 

of L{Geohash}es. 

 

@raise TypeError: The B{C{geohash}} is not a L{Geohash}, 

C{LatLon} or C{str}. 

 

@JSname: I{neighbours}. 

''' 

return _2Geohash(geohash).neighbors 

 

 

def precision(res1, res2=None): 

'''Determine the L{Geohash} precisions to meet a given (geographic) 

resolutions. 

 

@arg res1: The required, primary (longitudinal) resolution (C{degrees}). 

@kwarg res2: Optional, required, secondary (latitudinal resolution (C{degrees}). 

 

@return: The L{Geohash} precision or length (C{int} 1..12). 

 

@raise ValueError: Invalid B{C{res1}} or B{C{res2}}. 

 

@see: C++ class U{Geohash 

<https://GeographicLib.SourceForge.io/html/classGeographicLib_1_1Geohash.html>}. 

''' 

r1 = Scalar_(res1, name='res1') 

r2 = r1 if res2 is None else Scalar_(res2, name='res2') 

for p in range(1, _MaxPrec): 

if resolution2(p, None if res2 is None else p) <= (r1, r2): 

return p 

return _MaxPrec 

 

 

def resolution2(prec1, prec2=None): 

'''Determine the (geographic) resolutions of given L{Geohash} 

precisions. 

 

@arg prec1: The given primary (longitudinal) precision 

(C{int} 1..12). 

@kwarg prec2: Optional, secondary (latitudinal) precision 

(C{int} 1..12). 

 

@return: 2-Tuple (C{res1, res2}) with the (geographic) resolutions 

(C{degrees}) where C{res2} is C{res1} if no I{prec2} is 

given. 

 

@raise ValueError: Invalid B{C{prec1}} or B{C{prec2}}. 

 

@see: C++ class U{Geohash 

<https://GeographicLib.SourceForge.io/html/classGeographicLib_1_1Geohash.html>}. 

''' 

res1, res2 = _360_0, _180_0 

 

if prec1: 

p = 5 * max(0, min(Int(prec1, name='prec1', Error=GeohashError), _MaxPrec)) 

res1 = res2 = ldexp(res1, -(p - p // 2)) 

 

if prec2: 

p = 5 * max(0, min(Int(prec2, name='prec2', Error=GeohashError), _MaxPrec)) 

res2 = ldexp(res2, -(p // 2)) 

 

return res1, res2 

 

 

def sizes(geohash): 

'''Return the lat- and longitudinal size of this L{Geohash} cell. 

 

@arg geohash: Cell for which size are required (L{Geohash} or 

C{str}). 

 

@return: A L{LatLon2Tuple}C{(lat, lon)} with the latitudinal 

height and longitudinal width in (C{meter}). 

 

@raise TypeError: The B{C{geohash}} is not a L{Geohash}, 

C{LatLon} or C{str}. 

''' 

return _2Geohash(geohash).sizes 

 

 

__all__ += _ALL_OTHER(bounds, # functions 

decode, decode_error, distance1, distance2, distance3, 

encode, neighbors, precision, resolution2, 

sizes) + _ALL_DOCS(Neighbors8Dict) 

 

# **) MIT License 

# 

# Copyright (C) 2016-2020 -- mrJean1 at Gmail -- All Rights Reserved. 

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

# 

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