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Geohash

From Rosetta Code
Geohash is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Geohashes are used to represent standard latitude and longitude coordinates as single values in the form of a simple string -- using the digits (0-9) and the letters (B-Z excluding I, L, O). They can vary in length, with more characters in the string representing more precision.


Task

Generate a Geohash with a desired precision from a coordinate represented as an array of two floating point numbers, latitude and longitude. (Ideally double precision).


Example 1:
print (encodeGeohash (for: [51.433718, -0.214126], withPrecision: 2))
// Result: "gc" (all of Ireland, most of England and Wales, small part of Scotland)
Example 2:
print (encodeGeohash (for: [51.433718, -0.214126], withPrecision: 9))
// Result: "gcpue5hp4" (the umpire's chair on Center Court at Wimbledon)


From the Wikipedia page, geohashes can be "useful in database systems where queries on a single index are much easier or faster than multiple-index queries."


Extra credit

Provide a decode function to convert a geohash code back to latitude and longitude, expressed either as ranges or in median +/- deviation format.


Reference


Factor[edit]

Factor comes with the geohash vocabulary. See the implementation here.

Works with: Factor version 0.99 2020-03-02
USING: formatting generalizations geohash io kernel sequences ;
 
: encode-geohash ( latitude longitude precision -- str )
[ >geohash ] [ head ] bi* ;
 
! Encoding
51.433718 -0.214126 2
51.433718 -0.214126 9
57.649110 10.407440 11
[
3dup encode-geohash
"geohash for [%f, %f], precision %2d = %s\n" printf
] 3 3 mnapply nl
 
! Decoding
"u4pruydqqvj" dup geohash>
"coordinates for %s ~= [%f, %f]\n" printf
Output:
geohash for [51.433718, -0.214126], precision  2 = gc
geohash for [51.433718, -0.214126], precision  9 = gcpue5hp4
geohash for [57.649110, 10.407440], precision 11 = u4pruydqqvj

coordinates for u4pruydqqvj ~= [57.649110, 10.407439]

F#[edit]

 
// Create a geoHash String. Nigel Galloway: June 26th., 2020
let fG n g=Seq.unfold(fun(α,β)->let τ=(α+β)/2.0 in Some(if τ>g then (0,(α,τ)) else (1,(τ,b)))) n
let fLat, fLon = fG (-90.0,90.0), fG (-180.0,180.0)
let fN n g z=Seq.zip(fLat n)(fLon g)|>Seq.collect(fun(n,g)->seq{yield g;yield n})|>Seq.take(z*5)|>Seq.splitInto z
let fI=Array.fold2 (fun Σ α β->Σ+α*β) 0 [|16; 8; 4; 2; 1|]
let geoHash n g z=let N="0123456789bcdefghjkmnpqrstuvwxyz" in [|for τ in fN n g z do yield N.[fI τ]|] |> System.String
printfn "%s\n%s\n%s" (geoHash 51.433718 -0.214126 2) (geoHash 51.433718 -0.214126 9) (geoHash 57.64911 10.40744 11)
 
Output:
gc
gcpue5hp4
u4pruydqqvj

Go[edit]

Translation of: Swift
package main
 
import (
"fmt"
"strings"
)
 
type Location struct{ lat, lng float64 }
 
func (loc Location) String() string { return fmt.Sprintf("[%f, %f]", loc.lat, loc.lng) }
 
type Range struct{ lower, upper float64 }
 
var gBase32 = "0123456789bcdefghjkmnpqrstuvwxyz"
 
func encodeGeohash(loc Location, prec int) string {
latRange := Range{-90, 90}
lngRange := Range{-180, 180}
var hash strings.Builder
hashVal := 0
bits := 0
even := true
for hash.Len() < prec {
val := loc.lat
rng := latRange
if even {
val = loc.lng
rng = lngRange
}
mid := (rng.lower + rng.upper) / 2
if val > mid {
hashVal = (hashVal << 1) + 1
rng = Range{mid, rng.upper}
if even {
lngRange = Range{mid, lngRange.upper}
} else {
latRange = Range{mid, latRange.upper}
}
} else {
hashVal <<= 1
if even {
lngRange = Range{lngRange.lower, mid}
} else {
latRange = Range{latRange.lower, mid}
}
}
even = !even
if bits < 4 {
bits++
} else {
bits = 0
hash.WriteByte(gBase32[hashVal])
hashVal = 0
}
}
return hash.String()
}
 
func main() {
locs := []Location{
{51.433718, -0.214126},
{51.433718, -0.214126},
{57.64911, 10.40744},
}
precs := []int{2, 9, 11}
 
for i, loc := range locs {
geohash := encodeGeohash(loc, precs[i])
fmt.Printf("geohash for %v, precision %-2d = %s\n", loc, precs[i], geohash)
}
}
Output:
geohash for [51.433718, -0.214126], precision 2  = gc
geohash for [51.433718, -0.214126], precision 9  = gcpue5hp4
geohash for [57.649110, 10.407440], precision 11 = u4pruydqqvj

Julia[edit]

Translation of: Python
const ch32 = "0123456789bcdefghjkmnpqrstuvwxyz"
const bool2ch = Dict(string(i-1, base=2, pad=5) => ch for (i, ch) in enumerate(ch32))
const ch2bool = Dict(v => k for (k, v) in bool2ch)
 
function bisect(val, mn, mx, bits)
mid = (mn + mx) / 2
if val < mid
bits <<= 1 # push 0
mx = mid # range lower half
else
bits = (bits << 1) | 1 # push 1
mn = mid # range upper half
end
return mn, mx, bits
end
 
function encoder(lat, lng, pre)
latmin, latmax = -90, 90
lngmin, lngmax = -180, 180
bits = Int128(0)
for i in 0:5*pre-1
if i % 2 != 0
# odd bit: bisect latitude
latmin, latmax, bits = bisect(lat, latmin, latmax, bits)
else
# even bit: bisect longitude
lngmin, lngmax, bits = bisect(lng, lngmin, lngmax, bits)
end
end
# Bits to characters
b = string(bits, base=2, pad=5*pre)
geo = [bool2ch[b[i*5+1:i*5+5]] for i in 0:pre-1]
return prod(geo)
end
 
function decoder(geo)
minmaxes, latlong = [[-90.0, 90.0], [-180.0, 180.0]], 2
for c in geo, bit in ch2bool[c]
minmaxes[latlong][bit == '1' ? 1 : 2] = sum(minmaxes[latlong]) / 2
latlong = 3 - latlong
end
return minmaxes
end
 
for ((lat, lng), pre) in [([51.433718, -0.214126], 2),
([51.433718, -0.214126], 9),
([57.64911, 10.40744] , 11),
([57.64911, 10.40744] , 22)]
encoded = encoder(lat, lng, pre)
println("encoder(lat=$lat, lng=$lng, pre=$pre) = ", encoded)
println("decoded = ", decoder(encoded))
end
 
Output:
encoder(lat=51.433718, lng=-0.214126, pre=2) = gc
decoded = [[50.625, 56.25], [-11.25, 0.0]]
encoder(lat=51.433718, lng=-0.214126, pre=9) = gcpue5hp4
decoded = [[51.43369674682617, 51.43373966217041], [-0.21414756774902344, -0.21410465240478516]]
encoder(lat=57.64911, lng=10.40744, pre=11) = u4pruydqqvj
decoded = [[57.649109959602356, 57.64911130070686], [10.407439023256302, 10.40744036436081]]
encoder(lat=57.64911, lng=10.40744, pre=22) = u4pruydqqvj8pr9yc27rjr
decoded = [[57.64911, 57.64911000000001], [10.407439999999998, 10.407440000000008]]

Perl[edit]

Translation of: Raku
use strict;
use warnings;
use feature 'say';
use List::AllUtils qw<sum max natatime>;
 
my @Geo32 = <0 1 2 3 4 5 6 7 8 9 b c d e f g h j k m n p q r s t u v w x y z>;
 
sub geo_encode {
my( $latitude, $longitude, $precision ) = @_;
my @coord = ($latitude, $longitude);
my @range = ([-90, 90], [-180, 180]);
my($which,$value) = (1, '');
while (length($value) < $precision * 5) {
my $mid = sum(@{$range[$which]}) / 2;
$value .= my $upper = $coord[$which] <= $mid ? 0 : 1;
$range[$which][$upper ? 0 : 1] = $mid;
$which = $which ? 0 : 1;
}
my $enc;
my $iterator = natatime 5, split '', $value;
while (my @n = $iterator->()) {
$enc .= $Geo32[ord pack 'B8', '000' . join '', @n]; # binary to decimal, very specific to the task
}
$enc
}
 
sub geo_decode {
my($geo) = @_;
my @range = ([-90, 90], [-180, 180]);
my(%Geo32,$c); $Geo32{$_} = $c++ for @Geo32;
my $which = 1;
for ( split '', join '', map { sprintf '%05b', $_ } @Geo32{split '', $geo} ) {
$range[$which][$_] = sum(@{$range[$which]}) / 2;
$which = $which ? 0 : 1;
}
@range
}
 
for ([51.433718, -0.214126, 2, 'Ireland, most of England and Wales, small part of Scotland'],
[51.433718, -0.214126, 9, "the umpire's chair on Center Court at Wimbledon"],
[51.433718, -0.214126, 17, 'likely an individual molecule of the chair'],
[57.649110, 10.407440, 11, 'Wikipedia test value - Råbjerg Mile in Denmark'],
[59.115800, -151.687312, 7, 'Perl Island, Alaska'],
[38.743586, -109.499336, 8, 'Delicate Arch, Utah'],
) {
my($lat, $long, $precision, $description) = @$_;
my $enc = geo_encode($lat, $long, $precision);
say "\n$lat, $long, $precision ($description):" .
"\ngeo-encoded: $enc\n" .
'geo-decoded: ' . join ', ',
map { sprintf("%[email protected]{[max(3,$precision-3)]}f", ( -($$_[0] + $$_[1]) / 2)) .
' ± ' . sprintf('%.3e', (abs($$_[0] - $$_[1]) / 2))
} geo_decode($enc);}
Output:
51.433718, -0.214126, 2 (Ireland, most of England and Wales, small part of Scotland):
geo-encoded: gc
geo-decoded: 53.438 ± 2.812e+00,  -5.625 ± 5.625e+00

51.433718, -0.214126, 9 (the umpire's chair on Center Court at Wimbledon):
geo-encoded: gcpue5hp4
geo-decoded: 51.433718 ± 2.146e-05,  -0.214126 ± 2.146e-05

51.433718, -0.214126, 17 (likely an individual molecule of the chair):
geo-encoded: gcpue5hp4ebnf8unc
geo-decoded: 51.43371800000523 ± 2.046e-11,  -0.21412600000303 ± 2.046e-11

57.64911, 10.40744, 11 (Wikipedia test value - Råbjerg Mile in Denmark):
geo-encoded: u4pruydqqvj
geo-decoded: 57.64911063 ± 6.706e-07,  10.40743969 ± 6.706e-07

59.1158, -151.687312, 7 (Perl Island, Alaska):
geo-encoded: bds0k38
geo-decoded: 59.1154 ± 6.866e-04,  -151.6875 ± 6.866e-04

38.743586, -109.499336, 8 (Delicate Arch, Utah):
geo-encoded: 9wfhkm11
geo-decoded: 38.74354 ± 8.583e-05,  -109.49919 ± 1.717e-04

Phix[edit]

constant gBase32 = "0123456789bcdefghjkmnpqrstuvwxyz"
 
function encode_geohash(sequence location, integer precision)
sequence r = {{-90,90},{-180,180}} -- lat/long
integer ll = 2, -- " " "
hashval = 0, bits = 0
string hash = ""
while length(hash) < precision do
atom mid = sum(r[ll])/2,
gt = location[ll]>mid
hashval = hashval*2+gt
r[ll][2-gt] = mid
bits += 1
if bits=5 then
hash &= gBase32[hashval+1]
{hashval,bits} = {0,0}
end if
ll = 3-ll -- (1 <==> 2)
end while
return hash
end function
 
function decode_geohash(string hash)
-- output is {{lat_lo,lat_hi},{long_lo,long_hi}}
sequence r = {{-90,90},{-180,180}} -- lat/long
integer ll = 2 -- " " "
for h=1 to length(hash) do
string b = sprintf("%05b",find(hash[h],gBase32)-1)
for it=1 to 5 do
r[ll][2-(b[it]='1')] = sum(r[ll])/2
ll = 3-ll -- (1 <==> 2)
end for
end for
return r
end function
 
sequence tests = {{{51.433718, -0.214126}, 2},
{{51.433718, -0.214126}, 9},
{{57.64911, 10.40744 }, 11},
{{57.64911, 10.40744 }, 22}}
 
for i=1 to length(tests) do
{sequence location, integer precision} = tests[i]
string geohash = encode_geohash(location, precision)
printf(1,"geohash for %v, precision %d = %s\n",{location, precision, geohash})
tests[i] = geohash
end for
 
printf(1,"\ndecode tests:\n")
tests = append(tests,"ezs42")
for i=1 to length(tests) do
printf(1,"%-22s ==> %v\n",{tests[i],decode_geohash(tests[i])})
end for
Output:
geohash for {51.433718,-0.214126}, precision 2 = gc
geohash for {51.433718,-0.214126}, precision 9 = gcpue5hp4
geohash for {57.64911,10.40744}, precision 11 = u4pruydqqvj
geohash for {57.64911,10.40744}, precision 22 = u4pruydqqvj8pr9yc27rjr

decode tests:
gc                     ==> {{50.625,56.25},{-11.25,0}}
gcpue5hp4              ==> {{51.43369675,51.43373966},{-0.2141475677,-0.2141046524}}
u4pruydqqvj            ==> {{57.64910996,57.6491113},{10.40743902,10.40744036}}
u4pruydqqvj8pr9yc27rjr ==> {{57.64911,57.64911},{10.40744,10.40744}}
ezs42                  ==> {{42.58300781,42.62695312},{-5.625,-5.581054688}}

Not surprisingly, given the area it covers, "gc" is not even accurate to one significant digit, but a precision of 9 is accurate to 5 or 6 significant decimal digits, 11 to 6 or 7 digits, and 22 exceeds the natural 10 sig digs of %v. Note that 32-bit gives a last character of 'q' for the precision 22 test, for obvious reasons. The above results are from using the 64-bit interpreter.

PicoLisp[edit]

(scl 20)
(setq *GBASE32 (chop "0123456789bcdefghjkmnpqrstuvwxyz"))
(de encode (Lat Lng Prec)
(let
(Base (circ (list -180.0 180.0) (list -90.0 90.0))
Curr (circ Lng Lat)
Lst
(make
(do (* 5 Prec)
(let
(B (++ Base)
C (++ Curr)
M (/ (sum prog B) 2) )
(if (> C M)
(prog (set B M) (link 1))
(set (cdr B) M)
(link 0) ) ) ) ) )
(pack
(make
(for (L Lst L)
(link
(get
*GBASE32
(inc (bin (pack (cut 5 'L)))) ) ) ) ) ) ) )
(println (encode 51.433718 -0.214126 2))
(println (encode 51.433718 -0.214126 9))
(println (encode 57.649110 10.407440 11))
Output:
"gc"
"gcpue5hp4"
"u4pruydqqvj"

Python[edit]

ch32 = "0123456789bcdefghjkmnpqrstuvwxyz"
bool2ch = {f"{i:05b}": ch for i, ch in enumerate(ch32)}
ch2bool = {v : k for k, v in bool2ch.items()}
 
def bisect(val, mn, mx, bits):
mid = (mn + mx) / 2
if val < mid:
bits <<= 1 # push 0
mx = mid # range lower half
else:
bits = bits << 1 | 1 # push 1
mn = mid # range upper half
 
return mn, mx, bits
 
def encoder(lat, lng, pre):
latmin, latmax = -90, 90
lngmin, lngmax = -180, 180
bits = 0
for i in range(pre * 5):
if i % 2:
# odd bit: bisect latitude
latmin, latmax, bits = bisect(lat, latmin, latmax, bits)
else:
# even bit: bisect longitude
lngmin, lngmax, bits = bisect(lng, lngmin, lngmax, bits)
# Bits to characters
b = f"{bits:0{pre * 5}b}"
geo = (bool2ch[b[i*5: (i+1)*5]] for i in range(pre))
 
return ''.join(geo)
 
def decoder(geo):
minmaxes, latlong = [[-90.0, 90.0], [-180.0, 180.0]], True
for c in geo:
for bit in ch2bool[c]:
minmaxes[latlong][bit != '1'] = sum(minmaxes[latlong]) / 2
latlong = not latlong
 
return minmaxes
 
if __name__ == '__main__':
for (lat, lng), pre in [([51.433718, -0.214126], 2),
([51.433718, -0.214126], 9),
([57.64911, 10.40744] , 11),
([57.64911, 10.40744] , 22)]:
print("encoder(lat=%f, lng=%f, pre=%i) = %r"
 % (lat, lng, pre, encoder(lat, lng, pre)))
Output:
encoder(lat=51.433718, lng=-0.214126, pre=2) = 'gc'
encoder(lat=51.433718, lng=-0.214126, pre=9) = 'gcpue5hp4'
encoder(lat=57.649110, lng=10.407440, pre=11) = 'u4pruydqqvj'
encoder(lat=57.649110, lng=10.407440, pre=22) = 'u4pruydqqvj8pr9yc27rjr'

Note: The precision can be increased but would need lattitude and longitude expressed with more precision than floats, e.g. fractions or decimals for more accurate results. (but the encoder function would not need changing due to Duck Typing).

Raku[edit]

Module based[edit]

Reference: Used this for verification.

#20200615 Raku programming solution
 
use Geo::Hash;
 
# task example 1 : Ireland, most of England and Wales, small part of Scotland
say geo-encode(51.433718e0, -0.214126e0, 2);
 
# task example 2 : the umpire's chair on Center Court at Wimbledon
say geo-encode(51.433718e0, -0.214126e0, 9);
 
# Lake Raku is an artificial lake in Tallinn, Estonia
# https://goo.gl/maps/MEBXXhiFbN8WMo5z8
say geo-encode(59.358639e0, 24.744778e0, 4);
 
# Village Raku is a development committee in north-western Nepal
# https://goo.gl/maps/33s7k2h3UrHCg8Tb6
say geo-encode(29.2021188e0, 81.5324561e0, 4);
Output:
gc
gcpue5hp4
ud99
tv1y

Roll your own[edit]

Alternately, a roll-your-own version that will work with any Real coordinate, not just floating point values, and thus can return ridiculous precision. The geo-decode routine returns the range in which the actual value will be found; converted here to the mid-point with the interval size. Probably better to specify an odd precision so the error interval ends up the same for both latitude and longitude.

my @Geo32 = <0 1 2 3 4 5 6 7 8 9 b c d e f g h j k m n p q r s t u v w x y z>;
 
sub geo-encode ( Rat(Real) $latitude, Rat(Real) $longitude, Int $precision = 9 ) {
my @coord = $latitude, $longitude;
my @range = [-90, 90], [-180, 180];
my $which = 1;
my $value = '';
while $value.chars < $precision * 5 {
my $mid = @range[$which].sum / 2;
$value ~= my $upper = +(@coord[$which] > $mid);
@range[$which][not $upper] = $mid;
$which = not $which;
}
@Geo32[$value.comb(5)».parse-base(2)].join;
}
 
sub geo-decode ( Str $geo ) {
my @range = [-90, 90], [-180, 180];
my $which = 1;
my %Geo32 = @Geo32.antipairs;
for %Geo32{$geo.comb}».fmt('%05b').join.comb {
@range[$which][$_] = @range[$which].sum / 2;
$which = not $which;
}
@range
}
 
# TESTING
 
for 51.433718, -0.214126, 2, # Ireland, most of England and Wales, small part of Scotland
51.433718, -0.214126, 9, # the umpire's chair on Center Court at Wimbledon
51.433718, -0.214126, 17, # likely an individual molecule of the chair
57.649110, 10.407440, 11, # Wikipedia test value - Råbjerg Mile in Denmark
59.358639, 24.744778, 7, # Lake Raku in Estonia
29.2021188, 81.5324561, 7 # Village Raku in Nepal
-> $lat, $long, $precision {
say "$lat, $long, $precision:\ngeo-encoded: ",
my $enc = geo-encode $lat, $long, $precision;
say 'geo-decoded: ', geo-decode($enc).map( {-.sum/2 ~ ' ± ' ~
(abs(.[0]-.[1])/2).Num.fmt('%.3e')} ).join(', ') ~ "\n";
}
51.433718, -0.214126, 2:
geo-encoded: gc
geo-decoded: 53.4375 ± 2.813e+00,  -5.625 ± 5.625e+00

51.433718, -0.214126, 9:
geo-encoded: gcpue5hp4
geo-decoded: 51.4337182 ± 2.146e-05,  -0.21412611 ± 2.146e-05

51.433718, -0.214126, 17:
geo-encoded: gcpue5hp4ebnf8unc
geo-decoded: 51.43371800000523 ± 2.046e-11,  -0.21412600000303 ± 2.046e-11

57.64911, 10.40744, 11:
geo-encoded: u4pruydqqvj
geo-decoded: 57.64911063 ± 6.706e-07,  10.407439694 ± 6.706e-07

59.358639, 24.744778, 7:
geo-encoded: ud99ejf
geo-decoded: 59.358444 ± 6.866e-04,  24.744644 ± 6.866e-04

29.2021188, 81.5324561, 7:
geo-encoded: tv1ypk4
geo-decoded: 29.202347 ± 6.866e-04,  81.532974 ± 6.866e-04

Swift[edit]

let base32 = "0123456789bcdefghjkmnpqrstuvwxyz" // no "a", "i", "l", or "o"
 
extension String {
subscript(i: Int) -> String {
String(self[index(startIndex, offsetBy: i)])
}
}
 
struct Coordinate {
var latitude: Double
var longitude: Double
 
func toString() -> String {
var latitudeHemisphere = ""
var longitudeHemisphere = ""
 
latitudeHemisphere = latitude < 0 ? " S" : " N"
longitudeHemisphere = longitude < 0 ? " W" : " E"
 
return "\(abs(latitude))\(latitudeHemisphere), \(abs(longitude))\(longitudeHemisphere)"
}
}
 
func encodeGeohash (for coordinate: Coordinate, withPrecision precision: Int = 9) -> String {
var latitudeRange = -90.0...90.0
var longitudeRange = -180...180.0
 
var hash = ""
var hashVal = 0
var bits = 0
var even = true
 
while (hash.count < precision) {
let val = even ? coordinate.longitude: coordinate.latitude
var range = even ? longitudeRange : latitudeRange
let mid = (range.lowerBound + range.upperBound) / 2
 
if (val > mid) {
hashVal = (hashVal << 1) + 1
range = mid...range.upperBound
 
if even { longitudeRange = mid...longitudeRange.upperBound }
else { latitudeRange = mid...latitudeRange.upperBound }
} else {
hashVal = (hashVal << 1) + 0
range = range.lowerBound...mid
 
if even { longitudeRange = longitudeRange.lowerBound...mid }
else { latitudeRange = latitudeRange.lowerBound...mid }
}
 
even = !even
 
if (bits < 4) {
bits += 1
} else {
bits = 0
hash += base32[hashVal]
hashVal = 0
}
}
return hash
}
 
let coordinate1 = Coordinate(latitude: 51.433718, longitude: -0.214126)
let coordinate2 = Coordinate(latitude: 57.649110, longitude: 10.407440)
 
print ("Geohash for: \(coordinate1.toString()), precision = 5 : \(encodeGeohash(for: coordinate, withPrecision: 5))")
print ("Geohash for: \(coordinate1.toString()), precision = 9 : \(encodeGeohash(for: coordinate))")
print ("Geohash for: \(coordinate2.toString()), precision = 11 : \(encodeGeohash(for: coordinate, withPrecision: 11))")
 
 
Output:
Geohash for: 51.433718 N, 0.214126 W, precision = 5 : gcpue
Geohash for: 51.433718 N, 0.214126 W, precision = 9 : gcpue5hp4
Geohash for: 57.64911 N, 10.40744 E, precision = 11 : u4pruydqqvj

Wren[edit]

Translation of: Swift
Library: Wren-fmt
import "/fmt" for Fmt
 
var gBase32 = "0123456789bcdefghjkmnpqrstuvwxyz"
 
var encodeGeohash = Fn.new { |location, prec|
var latRange = -90..90
var lngRange = -180..180
var hash = ""
var hashVal = 0
var bits = 0
var even = true
while (hash.count < prec) {
var val = even ? location[1] : location[0]
var rng = even ? lngRange : latRange
var mid = (rng.from + rng.to) / 2
if (val > mid) {
hashVal = hashVal*2 + 1
rng = mid..rng.to
if (even) lngRange = mid..lngRange.to else latRange = mid..latRange.to
} else {
hashVal = hashVal * 2
if (even) lngRange = lngRange.from..mid else latRange = latRange.from..mid
}
even = !even
if (bits < 4) {
bits = bits + 1
} else {
bits = 0
hash = hash + gBase32[hashVal]
hashVal = 0
}
}
return hash
}
 
var data = [
[[51.433718, -0.214126], 2],
[[51.433718, -0.214126], 9],
[[57.64911, 10.40744 ], 11]
]
 
for (d in data) {
var geohash = encodeGeohash.call(d[0], d[1])
var loc = "[%(Fmt.f(9, d[0][0], 6)), %(Fmt.f(9, d[0][1], 6))]"
System.print("geohash for %(loc), precision %(Fmt.d(-2, d[1])) = %(geohash)")
}
Output:
geohash for [51.433718, -0.214126], precision 2  = gc
geohash for [51.433718, -0.214126], precision 9  = gcpue5hp4
geohash for [57.649110, 10.407440], precision 11 = u4pruydqqvj