First of all, Hello I am working on node.js javascript on interior positioning with Ibeacon. As a helper in my work: I use Evothings Studio. I'm transferring my codes to Evothings studio and viewing my work from my android and ios mobile phone. Now I want to tell you the problem I've had. According to RSSI Signal level, I find the distance is not very accurate in the calculations. I want to use Kalman Filter to clear the noises of this signal level (RSSI). This article describes the use of the kalman filter in Javascript. It is said to be easy to implement but I could not start practicing. "" Kalman Filter library: "https://github.com/wouterbulten/kalmanjs". How do I clear the noise from RSSI signals with this kalman filter? How do I apply the Kalman filter to these codes?
var app = (function()
{
// Application object.
var app = {};
// History of enter/exit events.
var mRegionEvents = [];
// Nearest ranged beacon.
var mNearestBeacon = null;
// Timer that displays nearby beacons.
var mNearestBeaconDisplayTimer = null;
// Background flag.
var mAppInBackground = false;
// Background notification id counter.
var mNotificationId = 0;
// Mapping of region event state names.
// These are used in the event display string.
var mRegionStateNames =
{
'CLRegionStateInside': 'Enter',
'CLRegionStateOutside': 'Exit'
};
// Here monitored regions are defined.
// TODO: Update with uuid/major/minor for your beacons.
// You can add as many beacons as you want to use.
var mRegions =
[
{
id: 'BEACON1',
uuid: 'fda50693-a4e2-4fb1-afcf-c6eb07647825',
major: 10035,
minor: 56498
},
{
id: 'region2',
uuid: 'f7826da6-4fa2-4e98-8024-bc5b71e0893e',
major: 60378,
minor: 22122
}
];
// Region data is defined here. Mapping used is from
// region id to a string. You can adapt this to your
// own needs, and add other data to be displayed.
// TODO: Update with major/minor for your own beacons.
var mRegionData =
{
'BEACON1': 'WGX_BEACON1',
'region2': 'Region Two'
};
app.initialize = function()
{
document.addEventListener('deviceready', onDeviceReady, false);
document.addEventListener('pause', onAppToBackground, false);
document.addEventListener('resume', onAppToForeground, false);
};
function onDeviceReady()
{
startMonitoringAndRanging();
startNearestBeaconDisplayTimer();
displayRegionEvents();
}
function onAppToBackground()
{
mAppInBackground = true;
stopNearestBeaconDisplayTimer();
}
function onAppToForeground()
{
mAppInBackground = false;
startNearestBeaconDisplayTimer();
displayRegionEvents();
}
function startNearestBeaconDisplayTimer()
{
mNearestBeaconDisplayTimer = setInterval(displayNearestBeacon, 1000);
}
function stopNearestBeaconDisplayTimer()
{
clearInterval(mNearestBeaconDisplayTimer);
mNearestBeaconDisplayTimer = null;
}
function startMonitoringAndRanging()
{
function onDidDetermineStateForRegion(result)
{
saveRegionEvent(result.state, result.region.identifier);
displayRecentRegionEvent();
}
function onDidRangeBeaconsInRegion(result)
{
updateNearestBeacon(result.beacons);
}
function onError(errorMessage)
{
console.log('Monitoring beacons did fail: ' + errorMessage);
}
// Request permission from user to access location info.
cordova.plugins.locationManager.requestAlwaysAuthorization();
// Create delegate object that holds beacon callback functions.
var delegate = new cordova.plugins.locationManager.Delegate();
cordova.plugins.locationManager.setDelegate(delegate);
// Set delegate functions.
delegate.didDetermineStateForRegion = onDidDetermineStateForRegion;
delegate.didRangeBeaconsInRegion = onDidRangeBeaconsInRegion;
// Start monitoring and ranging beacons.
startMonitoringAndRangingRegions(mRegions, onError);
}
function startMonitoringAndRangingRegions(regions, errorCallback)
{
// Start monitoring and ranging regions.
for (var i in regions)
{
startMonitoringAndRangingRegion(regions[i], errorCallback);
}
}
function startMonitoringAndRangingRegion(region, errorCallback)
{
// Create a region object.
var beaconRegion = new cordova.plugins.locationManager.BeaconRegion(
region.id,
region.uuid,
region.major,
region.minor);
// Start ranging.
cordova.plugins.locationManager.startRangingBeaconsInRegion(beaconRegion)
.fail(errorCallback)
.done();
// Start monitoring.
cordova.plugins.locationManager.startMonitoringForRegion(beaconRegion)
.fail(errorCallback)
.done();
}
function saveRegionEvent(eventType, regionId)
{
// Save event.
mRegionEvents.push(
{
type: eventType,
time: getTimeNow(),
regionId: regionId
});
// Truncate if more than ten entries.
if (mRegionEvents.length > 10)
{
mRegionEvents.shift();
}
}
function getBeaconId(beacon)
{
return beacon.uuid + ':' + beacon.major + ':' + beacon.minor;
}
function isSameBeacon(beacon1, beacon2)
{
return getBeaconId(beacon1) == getBeaconId(beacon2);
}
function isNearerThan(beacon1, beacon2)
{
return beacon1.accuracy > 0
&& beacon2.accuracy > 0
&& beacon1.accuracy < beacon2.accuracy;
}
function updateNearestBeacon(beacons)
{
for (var i = 0; i < beacons.length; ++i)
{
var beacon = beacons[i];
if (!mNearestBeacon)
{
mNearestBeacon = beacon;
}
else
{
if (isSameBeacon(beacon, mNearestBeacon) ||
isNearerThan(beacon, mNearestBeacon))
{
mNearestBeacon = beacon;
}
}
}
}
function displayNearestBeacon()
{
if (!mNearestBeacon) { return; }
// Clear element.
$('#beacon').empty();
// Update element.
var element = $(
'<li>'
+ '<strong>BEACON1</strong><br />'
+ 'UUID: ' + mNearestBeacon.uuid + '<br />'
+ 'Major: ' + mNearestBeacon.major + '<br />'
+ 'Minor: ' + mNearestBeacon.minor + '<br />'
+ 'Distance: ' + mNearestBeacon.accuracy + '<br />'
+ 'RSSI: ' + mNearestBeacon.rssi + '<br />'
+ '</li>'
);
$('#beacon').append(element);
}
function displayRecentRegionEvent()
{
if (mAppInBackground)
{
// Set notification title.
var event = mRegionEvents[mRegionEvents.length - 1];
if (!event) { return; }
var title = getEventDisplayString(event);
// Create notification.
cordova.plugins.notification.local.schedule({
id: ++mNotificationId,
title: title });
}
else
{
displayRegionEvents();
}
}
function displayRegionEvents()
{
// Clear list.
$('#events').empty();
// Update list.
for (var i = mRegionEvents.length - 1; i >= 0; --i)
{
var event = mRegionEvents[i];
var title = getEventDisplayString(event);
var element = $(
'<li>'
+ '<strong>' + title + '</strong>'
+ '</li>'
);
$('#events').append(element);
}
// If the list is empty display a help text.
if (mRegionEvents.length <= 0)
{
var element = $(
'<li>'
+ '<strong>'
+ 'İbeacon Taramasi Yapiliyor.'
+ '</strong>'
+ '</li>'
);
$('#events').append(element);
}
}
function getEventDisplayString(event)
{
return event.time + ': '
+ mRegionStateNames[event.type] + ' '
+ mRegionData[event.regionId];
}
function getTimeNow()
{
function pad(n)
{
return (n < 10) ? '0' + n : n;
}
function format(h, m, s)
{
return pad(h) + ':' + pad(m) + ':' + pad(s);
}
var d = new Date();
return format(d.getHours(), d.getMinutes(), d.getSeconds());
}
return app;
})();
app.initialize();After you complete experimenting with a Kalman Filter, you will likely find that the error in your distance estimates is still too high. This is because of the other sources of error besides random noise in your RSSI measurement, many of which can be a function of other variables (e.g. reflection, obstruction, antenna pattern variations) that affect the radio signal level as measured by the receiver.
In general, using direct distance calculations based on RSSI is at best accurate enough to estimate 0.5-2 meters at a true distance of 1 meter, and much lower accuracy at greater distances. This is true even after filtering out noise with a Kalman filter or running average. (Note iOS distance estimates use a 20 second running average on RSSI and RSSI field values on CLBeacon are averaged over one second.)
If using trilateration or similar approaches to calculate position, you will find that you can only get workable results at very short distances of no more than 1-2 meters.