I am doing an Indoor Navigation using I Beacon. I want to know the current location of the user. Is there any property for beacon like proximity or accuracy where i will get the distance of the beacon from the userLocation. Please help me to get the distance of the beacon from the userLocation. According to my knowledge beacons have accuracy, proximity and Received Signal Strength (RSSI). So it will be helpful if i get a clear idea of what these accuracy, proximity and RSSI means and how i can calculate or get the distance of the beacon from the userlocation.
Thanks in advance.
The CLBeacon class contains three properties which are related to the distance between the beacon transmitter and the receiving device:
rssi: The Received Signal Strength Indicator, measured in dBm, tells how strong the beacon signal was as averaged over the last one second ranging cycle. It originates from the radio receiver on the Bluetooth LE chip, and has a large amount of variation due to radio noise.
accuracy: This field provides a distance estimate in meters between the beacon and the receiving device. It is calculated using a mathematical formula from a running average of the rssi over 20 seconds, combined with a reference measurement of what the rssi is expected to be for the beacon at a distance of 1 meter. This reference measurement is transmitted inside every iBeacon packet. The field also has quite a bit of variance and error due to radio noise, signal multipath and reflections.
proximity: This field is derived from accuracy, and puts that value into one of three "buckets" depending on a range of values. "Immediate" is for an accuracy under 0.5 meters, "Far" is for an accuracy of 3 meters or more, and "Near" is for any value in between.
None of these fields can be used by themselves for indoor positioning, which is a much more complex subject. However, the first two fields can be useful inputs depending on the technique used.
More details are available here: http://developer.radiusnetworks.com/2014/12/04/fundamentals-of-beacon-ranging.html
I am working on indoorpin, which is a ready to use framework for iBeacon management. You can integrate it to your mobile app (IOS or Android) and use it with any iBeacon device. It consists of a web based CMS and SDK for mobile app. In CMS, you can see the real-time location of the mobile app user or you can get a report for historical data as heat-map or bubble map.
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I am working on app which used to detect beacons in iOS device using objective c. I have successfully done the scanning of beacons using core bluetooth and core location framework i.e did range beacons which provides an array of scanned beacons.
Case - I have to discard beacon scanned which are of distance more than 10 meters. So I have used RSSI value for that and calculated distance using formula and not considering beacons above that distance.
Problem - did range beacon is not providing the beacons distance more than 5-6 meters sometimes it provide around 8 meter beacon also.
Question - is there any specific range after that iOS discard the scanned beacons automatically?
It is not unusual for mobile devices to not be able to detect beacons beyond 8-10 meters. This has nothing to do with the operating system and is caused by the radio signal level falling below the noise floor as detected by the receiver.
The maximum distance a beacon can be detected is typically 40-50 meters in ideal clear line of sight conditions, but this also relies on the bluetooth transmitter being set to the maximum radio signal level allowed by international regulations, and the transmitter's antenna being directed generally toward the receiver.
It also relies on the receiving mobile device having it's antenna oriented toward the beacon transmitter and not blocked by a case or other radio obstruction.
Typically conditions you describe are caused by a beacon transmitting a signal far weaker than allowed by law. This may be adjusted on some models. Check the instructions from the beacon manufacturer.
Some mobile device.models have poor Bluetooth receiver antennas, although Apple devices are generally good. (Huawei Android devices are notoriously poor receivers.). If in doubt, try another device.
I am sorry if this has been asked in one way shape or another. I have started working with beacons, and in Xcode (Swift) - using CoreLocation. I really need a more accurate determination between the device and a beacon though. So far I have been using the standard proximity region values (Far, Near, and Immediate), however this just isn't cutting it at all. It seems far too unstable for the solution I am looking for - which is a simple one at best.
My scenario;
I need to display notifications, adverts, images etc to the users device when they are approximately 4 meters away from the beacon. This sounds simple enough, but when I found out that the only real solutions there are for beacons are those aforementioned proximity regions, I started to get worried because I need to only display to devices that are 3-5 meters away, no more.
I am aware of the accuracy property of the CLBeacon class, however Apple state it should not be used for accurate positioning of beacons, which I believe is what I am trying to achieve.
Is there a solution to this? Any help is appreciated!
Thanks,
Olly
There are limitations of physics when it comes to estimating distance with Bluetooth radio signals. Radio noise, signal reflections, and obstructions all affect the ability to estimate distance based on radio signal strength. It's OK to use beacons for estimating distance, but you must set your expectations appropriately.
Apple's algorithms in CoreLocation take a running average of the measured signal strength over 20 seconds or so, then come up with a distance estimate in meters that is put into the CLBeacon accuracy field. The results of this field are then used to come up with the proximity field. (0.5 meters or less means immediate, 0.5-3 meters means near, etc.)
When Apple recommends against using the accuracy field, it is simply trying to protect you against unrealistic expectations. This will never be an exact estimate in meters. Best results will come with a phone out of a pocket, with no obstructions between the beacon and the phone, and the phone relatively stationary. Under best conditions, you might expect to get distance estimates of +/- 1 meter at close distances of 3 meters or less. The further you get away, the more variation you will see.
You have to decide if this is good enough for your use case. If you can control the beacons there are a few things you can do to make the results as good as possible:
Turn the beacon transmitter power setting up as high as possible. This gives you a higher signal to noise ratio, hence better distance estimates.
Turn the advertising rate up as high as possible. This gives you more statistical samples, hence better distance estimates.
Place your beacons in locations where there will be as few obstructions as possible.
Always calibrate your beacon after making the changes like above. Calibration involves measuring the signal level at 1 meter and storing this as a calibration constant inside the beacon. Consult your beacon manufacturer instructions for details of how to do this calibration.
I want to use iPhone running a beacon scanning app to detect iBeacon to measure my distance changing. However I found the scanning rate is 1 per second, which cannot satisfy my moving speed. Some documents show scanning 1 time per second is determined by API that cannot be changed.
So do I have chance to speed up scanning rate?
There are two issues with the ranging beacons with CoreLocation for fast moving mobile devices:
As you mention, updates come only once per second.
The distance estimate in the CLBeacon accuracy field is based on the running average of the RSSI over 20 seconds, so it effectively gives you the average distance over that interval.
Unfortunately, you cannot change this -- it is how the API works. An alternative is to use the CoreBluetooth APIs, which can give you a call back once for each Bluetooth packet -- 10 times per second for a beacon advertising at that rate. Three obstacles with this:
You do not get a distance estimate with CoireBluetooth callbacks, just an RSSI measurement, so you must calculate your own distance from RSSI.
There is a lot of noise on RSSI, so using only a single reading the calculated distance estimate will be very inaccurate.
An iBeacon transmission cannot be parsed by iOS using CoreBluetooth, so you must use an alternate beacon format like AltBeacon.
You have to decide if these obstacles are acceptable for your use case.
I'm trying to estimate the distance from an iOS device to an iBeacon. I am aware that distance estimation is not super accurate, and I am also aware of this formula:
https://electronics.stackexchange.com/questions/83354/calculate-distance-from-rssi
I have found, through some research, that an iBeacon's BLE advertisement in fact contains data that represents the calibration value. That is to say, the RSSI determined at 1 meter away is actually broadcast by the beacon for all to see.
Now, I think the iOS must internally use this information to determine the Near, Far, Immediate, and Unknown categorizations of distance but I am not aware of any way to access this 1-meter RSSI directly.
My question is simply: Is there a way to get the distance estimate between an iOS device and a beacon WITHOUT having the 1-meter calibration value saved on the iOS device beforehand?
Some people say that the 'accuracy' field of the CLBeacon class is, in fact, the distance measurement to the beacon. The documentation does not support this statement, here's what it says:
accuracy The accuracy of the proximity value, measured in meters from
the beacon. (read-only)
#property (readonly, nonatomic) CLLocationAccuracy accuracy;
Discussion Indicates the one sigma horizontal accuracy in meters. Use
this property to differentiate between beacons with the same proximity
value. Do not use it to identify a precise location for the beacon.
Accuracy values may fluctuate due to RF interference.
A negative value in this property signifies that the actual accuracy
could not be determined.
There is a new iBeacon Document released by Apple on June 2, 2014 that states:
When building an application that uses either GPS or
beacon, it is important to consider this accuracy. The values
reported by the Core Location objects (the
horizontalAccuracy property in the CLLocation class, or
the accuracy property in the CLBeacon class) indicate this
level of uncertainty, or the margin of error. Both are
measured in meters. The higher the value, the lower the
certainty of the position of the device or beacon. Keep in
mind that depending on the physical surroundings a low
accuracy may not be possible.
I suspect that's Apple's 'confidence' metric when reading their CLProximity values. I interpret that as obtaining something like:
CLProximityNear with an accuracy value of 5; Apple pinpoints your position within a 5m margin of error.
The general sentiment I'm getting from my general analysis of sources is that using beacon technology for distance approximation is probably not the strength of the technology.
EDIT: Chaise Hocking from Shine Technologies in Melbourne has an insightful blog post that has some experiments and results regarding the accuracy property.
Is there a way to get the distance estimate between an iOS device and a beacon WITHOUT having the 1-meter calibration value saved on the iOS device beforehand?
YES, you simply read the CLBeacon accuracy field as you suspected. This is an estimate of the distance to the beacon in meters.
This estimate uses an undocumented calculation that is based on the RSSI measurements (likely a 30 second running average, perhaps discarding outliers) combined with the 1-meter RSSI calibration value embedded in the iBeacon advertisement. A port of this calculation to Android is shown here.
And, no, there is no way to read the calibration value from an app. It is obscured by iOS, which disallows seeing the details of iBeacon Bluetooth LE advertisements. See here for a detailed explanation.
We are having a issue with iBeacons.
App makes wrong guess sometimes as to which proximity region its in before eventually correcting itself. It sometimes shows Far when the Proximity is Near. And then later it flips back to Near.
The problem actually occurs when we need to fire an event when we are in the Near/Far/Immediate region. This doest happen in that way. App is likely to lose range of beacons for brief instances.
Are there any other way to solve this Issue.
It is normal for the Proximity estimate to fluctuate with radio noise, but your experience sounds extreme. What iBeacon brand are you using?
Make sure you are using an iBeacon with as fast enough transmission rate. Different iBeacons transmit advertisements at different frequencies from 30 times per second to once per second or less. Generally, faster transmission rates give you less noisy distance estimates because they give iOS more radio signal strength measurements to work with.
If an iBeacon transmits less than once per sec, you may get intermittent exit/entry events.
For your testing, Try an iOS-based iBeacon like Locate for iBeacon or EZBeacon to see if it helps. It is known to transmit 30x per second.
The proximity issue can be effected by advertising frequency as David has already said. The reason for this is that iOS takes an average of the RSSI readings overtime and uses these to find a final value, if you hold an iOS device in an ideal location, (i.e. clear line of site to the beacon) the result settles down over a few seconds of holding the device still. Apple describes the averaging as: "This value is the average RSSI value of the samples received since the range of the beacon was last reported to your app."
However a bigger factor can be fluctuations in the environment, the RSSI will change dramatically if an obstruction appears between the iBeacon and the iOS device, if the iBeacon and iOS device are both at a low level, this could be a person walking past. I have published some initial results using Estimote iBeacons that show changes in distance based on the device operator rotating 360 degrees. A distance change of +/- 2m is not an uncommon change in this circumstance and could result in the behaviour you observed if the iOS device is near the proximity region boundary.
This is Wojtek Borowicz, I'm a community evangelist at Estimote.
Calculating the exact proximity of a Beacon is based solely on the radio waves it’s broadcasting an is really hard. You encounter factors like multipath propagation, wave diffraction, absorption or interference. That’s exactly why iBeacon standard does not try to calculate the exact distance between a Beacon and the receiving device. Instead, it uses a value called RSSI (received signal strength indicator), which allows to estimate the proximity based on signal power. For calibration purposes, there’s also included a metric called Measured Power - but it’s nothing more than just RSSI measured 1 meter away from the Beacon. Even calibrated, RSSI might fluctuate heavily, due to the factors mentioned above.
The stability of the Beacon’s signal is also based on two main factors. One of them is advertising interval (frequency - the lower, the better signal) and broadcasting power (the higher the better signal). Improving them will allow for much better proximity reading, but will also strongly affect battery life.