function roundNumber(num) {
var dec = 3;
var result = Math.round(num*Math.pow(10,dec))/Math.pow(10,dec);
return result;
}
function watchCompass() {
debug.log("watchCompass");
var suc = function(a){
document.getElementById('compass_magnetic').innerHTML = roundNumber(a.magneticHeading);
document.getElementById('compass_true').innerHTML = roundNumber(a.trueHeading);
document.getElementById('compass_accuracy').innerHTML = roundNumber(a.headingAccuracy);
};
var fail = function(){};
var opt = {};
opt.frequency = 100;
timer = navigator.compass.watchHeading(suc,fail,opt);
}
<dl id="compass-data">
<dt>M:</dt><dd id="compass_magnetic"> </dd>
<dt>T:</dt><dd id="compass_true"> </dd>
<dt>A:</dt><dd id="compass_accuracy"> </dd>
</dl>
<a href="#" class="btn large" onclick="watchCompass();">Watch Compass</a>
