Once an app finds a beacon is possible to show both in a map (the device that found the beacon and the beacon itself)? If so how can i do that? I tried work with the distance bit with no success so far.
Unfortunately, you can't just find the exact location of an iBeacon once it's detected. You can only estimate its distance away from the device.
The proximity property tells you the relative distance (far, immediate, or close) that the beacon is away from the device while the accuracy property tells you how accurate that value is; so you can use proximity in combination with accuracy to get a general approximation of the distance. You could also potentially use these properties in combination with the RSSI, i.e. the received signal strength of the beacon, to further approximate the relative distance.
The device on the other hand can be mapped easily by turning on the map's showsUserLocation property.
I suppose your map is a MKMapView. If you know the precise location of the beacon (by having use a GPS to get the coordinates of the beacon when you have installed it) you can add an annotation on your MKMapView.
Take a look at MKMapView - (void)addAnnotation:(id < MKAnnotation >)annotation method for that.
If you don't have a database where to fetch the GPS coordinates of your beacons, there is no way to display them on a map as a beacon knows nothing about its surroundings.
By the way the accuracy property of a CLBeacon object isn't reliable enough for positioning.
Related
I want to locate an object position inside a house( one floor).
The object will have a iBeacon on it.
What are the best approach.
With api, i can get distance from the iBeacon, but this doesn't reflect position.
One idea was to have 4 fixed iBeacon on the floor, but seem's i can't get the distance from the moving iBeacon to a fixed.
Any idea?
iBeacon isn't the right technology for this - at least not with a single receiver.
iBeacon only gives you an approximate distance. If you have multiple beacons in known locations then you can try and triangulate the receiver's position but you can't use this information to determine the location of another transmitter in an unknown location - only estimate its distance from the receiver.
Even using known, fixed transmitters it is difficult to locate the receiver with any accuracy due to the nature of the Bluetooth signals.
If you had multiple iBeacon receivers on the floor at known locations then it might be possible to determine the location of the transmitter.
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.
I am using an iBeacon, and using triangulation and trilateration (or something similar), want to be able to locate an exact (or fairly accurate) distance between the iBeacon and user's device (in feet/metres/e.t.c). What is the best way to do this, and how would I do this?
I forgot to mention: I understand that it is possible to find proximity (i.e near, immediate, far, etc.), however as mentioned, ideally I am looking to find an accurate distance (maybe by combining RSSI, accuracy, and proximity values).
For this you should use RSSI (Received Signal Strength Indication) of an iBeacon. The signal strength determines how close or far it is from you. But the problem is that:
Every beacon's RSSI might differ distance, accuracy.
If beacon is behind the wall or any static obstacle the RSSI-Distance-Ratio will not work.
Therefore instead of Triangulation or Trilateration you should go for Fingerprinting. This will work better then rest of the techniques.
Place obstacles all around you.
Make reference points on your map.
Calibrate your app with that location i.e. Get the signal strengths from atleast 3 nearest iBeacons and save it against that reference points.
Do this for all other reference points.
(If you can) Do this twice or thrice and take average and store in database.
Now you have laid map of calibrated reference points. (This will handle all different RSSI-DIstance-Ratios of all the beacons)
Now whenever you are at any position compare it with the nearest point and you will get to know the closest location of your reference point.
If you are using google maps, the lat long they provide is upto six decimal place i.e. 0.11 meters which i think is preety much accurate in a room as well.
I guess this helps :)
Please mark this the right answer if it works.
In iOS the Core Location beacon information you get when you range a beacon includes both a "proximity" value (far/near/immediate) and an "accuracy" reading, which is actually approximate distance, in meters.
In order for the distance reading to be as accurate as possible, you should really calibrate your beacons. To do that, you put the beacon exactly 1 meter from the receiver and take a reading. The receiver gives you a "measured power" reading, which you then set on the transmitter. The measured power reading is used in calculating the distance reading.
Distance readings are very approximate, and are subject to interference from the surroundings.
The Apple sample app "AirLocate" shows working code for calibrating a beacon, and I believe it also displays
I've been working on a location based app recently and am noticing some strange values for CLLocation. I often get a horizontalAccuracy of 1414 and a verticalAccuracy of -1. Any clue what this indicates? As far as I can tell, these points are often very accurate. What is the difference between verticalAccuracy and horizontalAccuracy?
The -1 for verticalAccuracy indicates that the altitude in the CLLocation is not valid. You only get altitude with a 3D GPS position.
The 1414 for horizontalAccuracy indicates that the horizontal (lat/lon) position could be up to 1414m off (this is just an estimated error). This is probably a location determined by cell tower triangulation or WiFi location data. GPS locations usually report 100m or better.
To get a higher accuracy location (300m or better) you need to set desiredAccuracy and wait for the GPS receiver to lock onto at least 3 satellites (or 4 for a 3D fix). Until that happens CLLocationManager will give you the best it has which is WiFi or Cell tower triangulation results.
With a 3G GPS device (i.e. iPad 3G) is there a way to know if a reported CLLocation is based on a GPS signal, and not the inaccurate cellular data?
The CLLocation class has a method called -horizontalAccuracy:. This will give you some idea of the radius of accuracy of that measurement. This is probably better than asking just "is it GPS" because GPS readings can also be pretty inaccurate, depending on receiving conditions and satellite visibility.