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added project files
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David Troy committed May 30, 2008
1 parent f79174a commit 01a3a49
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216 changes: 216 additions & 0 deletions geohash.js
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var BASE32 = "0123456789bcdefghjkmnpqrstuvwxyz";
var NEIGHBORS = { right : { even : "bc01fg45238967deuvhjyznpkmstqrwx" },
left : { even : "238967debc01fg45kmstqrwxuvhjyznp" },
top : { even : "p0r21436x8zb9dcf5h7kjnmqesgutwvy" },
bottom : { even : "14365h7k9dcfesgujnmqp0r2twvyx8zb" } };
var BORDERS = { right : { even : "bcfguvyz" },
left : { even : "0145hjnp" },
top : { even : "prxz" },
bottom : { even : "028b" } };

NEIGHBORS.bottom.odd = NEIGHBORS.left.even;
NEIGHBORS.top.odd = NEIGHBORS.right.even;
NEIGHBORS.left.odd = NEIGHBORS.bottom.even;
NEIGHBORS.right.odd = NEIGHBORS.top.even;

BORDERS.bottom.odd = BORDERS.left.even;
BORDERS.top.odd = BORDERS.right.even;
BORDERS.left.odd = BORDERS.bottom.even;
BORDERS.right.odd = BORDERS.top.even;

var ZOOMLEVELS = { 3: 7, 4 : 10, 5 : 12, 6 : 15, 7 : 17, 8 : 17 };

BITS = [16, 8, 4, 2, 1];

function wheelZoom(a) { (a.detail || -a.wheelDelta) < 0 ? map.zoomIn() : map.zoomOut(); }

function sizeMap() {
map = new GMap2(document.getElementById("map"));

map.setCenter(new GLatLng(39.024,-76.51), 9);
map.addControl(new GSmallMapControl());
}

function refine_interval(interval, cd, mask) {
if (cd&mask)
interval[0] = (interval[0] + interval[1])/2;
else
interval[1] = (interval[0] + interval[1])/2;
}

function decodeGeoHash(geohash) {
var is_even = 1;
var lat = []; var lon = [];
lat[0] = -90.0; lat[1] = 90.0;
lon[0] = -180.0; lon[1] = 180.0;
lat_err = 90.0; lon_err = 180.0;

for (i=0; i<geohash.length; i++) {
c = geohash[i];
cd = BASE32.indexOf(c);
for (j=0; j<5; j++) {
mask = BITS[j];
if (is_even) {
lon_err /= 2;
refine_interval(lon, cd, mask);
} else {
lat_err /= 2;
refine_interval(lat, cd, mask);
}
is_even = !is_even;
}
}
lat[2] = (lat[0] + lat[1])/2;
lon[2] = (lon[0] + lon[1])/2;

return { latitude: lat, longitude: lon};
}

function encodeGeoHash(latitude, longitude) {
var is_even=1;
var i=0;
var lat = []; var lon = [];
var bit=0;
var ch=0;
var precision = 12;
geohash = "";

lat[0] = -90.0; lat[1] = 90.0;
lon[0] = -180.0; lon[1] = 180.0;

while (geohash.length < precision) {
if (is_even) {
mid = (lon[0] + lon[1]) / 2;
if (longitude > mid) {
ch |= BITS[bit];
lon[0] = mid;
} else
lon[1] = mid;
} else {
mid = (lat[0] + lat[1]) / 2;
if (latitude > mid) {
ch |= BITS[bit];
lat[0] = mid;
} else
lat[1] = mid;
}

is_even = !is_even;
if (bit < 4)
bit++;
else {
geohash += BASE32[ch];
bit = 0;
ch = 0;
}
}
return geohash;
}

function calculateHash(srcHash, dir) {
srcHash = srcHash.toLowerCase();
var lastChr = srcHash.charAt(srcHash.length-1);
var type = (srcHash.length % 2) ? 'odd' : 'even';
var base = srcHash.substring(0,srcHash.length-1);
if (BORDERS[dir][type].indexOf(lastChr)!=-1)
base = calculateHash(base, dir);
return base + BASE32[NEIGHBORS[dir][type].indexOf(lastChr)];
}

GeoHashBox.prototype.centerMap = function () {
map.setCenter(new GLatLng(this.centerPoint[0], this.centerPoint[1]), ZOOMLEVELS[this.geohash.length]);
}

GeoHashBox.prototype.showNeighbors = function () {
var geohashPrefix = this.geohash.substring(0,this.geohash.length-1);

this.neighbors.top = new GeoHashBox(calculateHash(this.geohash, 'top'));
this.neighbors.bottom = new GeoHashBox(calculateHash(this.geohash, 'bottom'));
this.neighbors.right = new GeoHashBox(calculateHash(this.geohash, 'right'));
this.neighbors.left = new GeoHashBox(calculateHash(this.geohash, 'left'));
this.neighbors.topleft = new GeoHashBox(calculateHash(this.neighbors.left.geohash, 'top'));
this.neighbors.topright = new GeoHashBox(calculateHash(this.neighbors.right.geohash, 'top'));
this.neighbors.bottomright = new GeoHashBox(calculateHash(this.neighbors.right.geohash, 'bottom'));
this.neighbors.bottomleft = new GeoHashBox(calculateHash(this.neighbors.left.geohash, 'bottom'));
}

GeoHashBox.prototype.plot = function () {
var polyline = new GPolygon([
this.corners.topleft,
this.corners.topright,
this.corners.bottomright,
this.corners.bottomleft,
this.corners.topleft
], "#007799", 3, 0.7, "#003366", 0.5, {geodesic:true});
map.addOverlay(polyline);
var marker = new LabeledMarker(new GLatLng(this.box.latitude[2],this.box.longitude[2]), this.options );
map.addOverlay(marker);
}

function GeoHashBox (geohash) {
this.geohash = geohash;
this.box = decodeGeoHash(geohash);
this.corners = {};
this.corners.topleft = new GLatLng(this.box.latitude[0], this.box.longitude[0]);
this.corners.topright = new GLatLng(this.box.latitude[1], this.box.longitude[0]);
this.corners.bottomright = new GLatLng(this.box.latitude[1], this.box.longitude[1]);
this.corners.bottomleft = new GLatLng(this.box.latitude[0], this.box.longitude[1]);

this.centerPoint = [ (this.box.latitude[0] + this.box.latitude[1])/2, (this.box.longitude[0] + this.box.longitude[1])/2];
this.options = {labelText : geohash};
var lastChr = this.geohash.charAt(this.geohash.length-1);
this.selfPos = BASE32.indexOf(lastChr);
this.neighbors = {};
this.plot();
}

function geocodeAddress () {
var address = document.getElementById("address").value;
var geocoder = new GClientGeocoder();
geocoder.getLatLng(address, plotGeoHash);
}

function plotGeoHash (gLatLng) {
var geohash = encodeGeoHash(gLatLng.lat(), gLatLng.lng());
document.getElementById("geoHash").value = geohash;
var resolution = document.getElementById("hashResolution").value;
geohash = geohash.substr(0,resolution);
var geoHashBox = new GeoHashBox(geohash);
geoHashBox.centerMap();
geoHashBox.showNeighbors();

boxList = document.getElementById("boxList");
boxList.innerHTML = "LEFT(geohash," + resolution + ") IN (";
var boxes = [];
for (var n in geoHashBox.neighbors) {
boxes.push("'"+geoHashBox.neighbors[n].geohash+"'");
}
boxList.innerHTML += boxes.join(',') + ")";

searchInfo = document.getElementById("searchInfo");
var xdistance = geoHashBox.neighbors.topleft.corners.topleft.distanceFrom(geoHashBox.neighbors.topright.corners.topright);
var ydistance = geoHashBox.neighbors.topleft.corners.topleft.distanceFrom(geoHashBox.neighbors.bottomleft.corners.bottomleft);
var searcharea = parseInt((xdistance/1000) * (ydistance/1000)*100)/100;
if (xdistance>2000) {
xdistance = parseInt(xdistance/10)/100;
ydistance = parseInt(ydistance/10)/100;
units = "km";
} else {
xdistance = parseInt(xdistance+0.5);
ydistance = parseInt(ydistance+0.5);
units = "m";
}

searchInfo.innerHTML = "w:" + xdistance + units + ", h:" + ydistance + units + " (" + searcharea + "km2)";
}

window.onload = function () {
if (GBrowserIsCompatible()) {
sizeMap();
GEvent.addDomListener(document.getElementById('map'), "DOMMouseScroll", wheelZoom);
GEvent.addDomListener(document.getElementById('map'), "mousewheel", wheelZoom);
} else {
alert("Sorry, your browser is lame!")
}

}
47 changes: 47 additions & 0 deletions index.html
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<html>
<head>
<title>geohash demonstrator</title>
<script src="http://maps.google.com/maps?file=api&amp;v=2&amp;key=ABQIAAAAS-9BXlmhAxzk5tMQ6009tBQ60YHOa08tQ3Rk7kk6p9CpE9bRLhRgOlUOLYUPHsGwp_XgmEwZWB1hnA&amp;hl=" type="text/javascript"/>
<script src="./geohash.js" type="text/javascript"/>
<script src="./labeledmarker.js" type="text/javascript"/>
<style>
body {
font-family: 'Helvetica';
font-weight: Bold;
color: white;
margin: 0px;
}
input {
font-family: 'Helvetica';
font-weight: Normal;
}
.LabeledMarker_markerLabel {
color: white;
font-size: 13px;
font-family: "helvetica neue";
text-transform: uppercase;
}
</style>
</head>
<body>
<div style="width:100%; background: #000; height: 10%; padding: 15px;">
<input type="text" value="1600 Pennsylvania Ave, Washington, DC" id="address" name="address" size="50">
<input type="text" value="" id="geoHash" name="geoHash">
<select id="hashResolution" name="hashResolution">
<option>3
<option>4
<option selected>5
<option>6
<option>7
<option>8
</select>

<input type="button" value="plot" onClick="geocodeAddress();">
<input type="button" value="clear" onClick="map.clearOverlays();">
<br>
<span id="boxList"></span><br/>
<span id="searchInfo"></span>
</div>
<div id="map" style="width:100%; height:90%;">
</body>
</html>

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