mirror of
https://github.com/jiawanlong/Cesium-Examples.git
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116 lines
2.8 KiB
JavaScript
116 lines
2.8 KiB
JavaScript
/*!
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* Copyright© 2008 David Troy
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*
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* geohash.js
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* github: https://github.com/davetroy/geohash-js
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* license: MIT License
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*
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*/
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BITS = [16, 8, 4, 2, 1];
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BASE32 = "0123456789bcdefghjkmnpqrstuvwxyz";
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NEIGHBORS = { right : { even : "bc01fg45238967deuvhjyznpkmstqrwx" },
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left : { even : "238967debc01fg45kmstqrwxuvhjyznp" },
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top : { even : "p0r21436x8zb9dcf5h7kjnmqesgutwvy" },
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bottom : { even : "14365h7k9dcfesgujnmqp0r2twvyx8zb" } };
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BORDERS = { right : { even : "bcfguvyz" },
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left : { even : "0145hjnp" },
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top : { even : "prxz" },
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bottom : { even : "028b" } };
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NEIGHBORS.bottom.odd = NEIGHBORS.left.even;
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NEIGHBORS.top.odd = NEIGHBORS.right.even;
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NEIGHBORS.left.odd = NEIGHBORS.bottom.even;
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NEIGHBORS.right.odd = NEIGHBORS.top.even;
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BORDERS.bottom.odd = BORDERS.left.even;
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BORDERS.top.odd = BORDERS.right.even;
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BORDERS.left.odd = BORDERS.bottom.even;
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BORDERS.right.odd = BORDERS.top.even;
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function refine_interval(interval, cd, mask) {
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if (cd&mask)
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interval[0] = (interval[0] + interval[1])/2;
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else
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interval[1] = (interval[0] + interval[1])/2;
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}
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function calculateAdjacent(srcHash, dir) {
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srcHash = srcHash.toLowerCase();
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var lastChr = srcHash.charAt(srcHash.length-1);
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var type = (srcHash.length % 2) ? 'odd' : 'even';
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var base = srcHash.substring(0,srcHash.length-1);
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if (BORDERS[dir][type].indexOf(lastChr)!=-1)
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base = calculateAdjacent(base, dir);
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return base + BASE32[NEIGHBORS[dir][type].indexOf(lastChr)];
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}
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function decodeGeoHash(geohash) {
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var is_even = 1;
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var lat = []; var lon = [];
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lat[0] = -90.0; lat[1] = 90.0;
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lon[0] = -180.0; lon[1] = 180.0;
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lat_err = 90.0; lon_err = 180.0;
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for (i=0; i<geohash.length; i++) {
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c = geohash[i];
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cd = BASE32.indexOf(c);
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for (j=0; j<5; j++) {
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mask = BITS[j];
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if (is_even) {
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lon_err /= 2;
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refine_interval(lon, cd, mask);
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} else {
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lat_err /= 2;
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refine_interval(lat, cd, mask);
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}
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is_even = !is_even;
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}
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}
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lat[2] = (lat[0] + lat[1])/2;
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lon[2] = (lon[0] + lon[1])/2;
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return { latitude: lat, longitude: lon};
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}
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function encodeGeoHash(latitude, longitude) {
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var is_even=1;
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var i=0;
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var lat = []; var lon = [];
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var bit=0;
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var ch=0;
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var precision = 12;
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geohash = "";
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lat[0] = -90.0; lat[1] = 90.0;
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lon[0] = -180.0; lon[1] = 180.0;
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while (geohash.length < precision) {
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if (is_even) {
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mid = (lon[0] + lon[1]) / 2;
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if (longitude > mid) {
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ch |= BITS[bit];
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lon[0] = mid;
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} else
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lon[1] = mid;
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} else {
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mid = (lat[0] + lat[1]) / 2;
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if (latitude > mid) {
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ch |= BITS[bit];
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lat[0] = mid;
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} else
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lat[1] = mid;
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}
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is_even = !is_even;
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if (bit < 4)
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bit++;
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else {
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geohash += BASE32[ch];
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bit = 0;
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ch = 0;
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}
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}
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return geohash;
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}
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