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Geosyl.js – Convert Latitude longitude Pairs to Readable Words
// Geosyl.js – Convert Latitude longitude Pairs to Readable Words.
// based on David Troy's https://github.com/davetroy/hash-js
// also see: http://www.movable-type.co.uk/scripts/hash.html
// Distributed under the MIT License
geosyl = (function(){
var bits = [32, 16, 8, 4, 2, 1],
vocals = 'aeiou'.split(''),
consonants = 'kgsztdnhfpmyr'.split(''),
syllables = [];
vocals.forEach(function(vocal){
consonants.forEach(function(consonant) {
syllables.push(consonant + vocal);
});
});
function refine_interval(interval, cd, mask) {
var mid = (interval[0] + interval[1]) / 2;
interval[cd & mask ? 0 : 1] = mid;
}
return {
decode: function (hash) {
hash = hash
.replace(/\W/g, '')
.toLowerCase()
.match(/\w{2}/g);
var isEven = 1,
lat = [-90, 90],
lng = [-180, 180],
mask,
part,
i;
for (i = 0; i < hash.length; i++) {
part = hash[i];
index = syllables.indexOf(part);
for (j = 0; j < bits.length; j++) {
mask = bits[j];
if (isEven) {
refine_interval(lng, index, mask);
} else {
refine_interval(lat, index, mask);
}
isEven = !isEven;
}
}
return [lat[0], lng[0], lat[1], lng[1]];
},
encode: function(latitude, longitude, precision) {
var isEven = true,
lat = [-90, 90],
lng = [-180, 180],
bit = 0,
index = 0,
hash = [],
mid;
precision = precision || 9;
while (hash.length < precision) {
if (isEven) {
mid = (lng[0] + lng[1]) / 2;
if (longitude > mid) {
index |= bits[bit];
lng[0] = mid;
} else
lng[1] = mid;
} else {
mid = (lat[0] + lat[1]) / 2;
if (latitude > mid) {
index |= bits[bit];
lat[0] = mid;
} else
lat[1] = mid;
}
isEven = !isEven;
if (bit < bits.length-1) {
bit++;
} else {
hash.push(syllables[index]);
bit = 0;
index = 0;
}
}
return hash.map(function(syllable, index) {
return syllable + ((
index % 3 == 2 &&
index < hash.length - 1
) ? ' ' : '');
}).join('');
}
}
})();
var lat = 51.5,
lng = 10,
hash = geosyl.encode(lat, lng),
bounds = geosyl.decode(hash);
console.log(lat, lng);
console.log(hash);
console.log(bounds);
console.log(Math.abs(bounds[0] - lat))
console.log(Math.abs(bounds[1] - lng))
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