We're using the iOS ibeacon APIs to wake up our app for vehicle bluetooth key and to enable the seamless walk-away features; Does the Measured Power value in the advertising packet affect an app’s background launch? If so, what is the mechanism? If not, what is the actual purpose of this field in Core Location? For different beacon devices/vehicle models, does this value need to be adjusted? For example, we have different vehicle models – should each model set this value based on actual calibration data? Our current understanding: Measured Power is typically used for our APP to do the distance estimation but we are not sure whether the system also uses it as a weighting factor for background wake‑ups or region triggers. We have noticed some discussions in forums about similar scenarios where it is mentioned that Measured Power needs to be set correctly.
As also stated in the specifications "Apple devices use the Measured Power value of a Proximity Beacon to help with ranging accuracy."
The CoreLocation API will launch your app when the system determines that the device is within range of the iBeacon. This determination is far from a simple no-signal -> yes-signal decision and it involves algorithms to make sure there are no false positives, etc.
The exact determination logic is not documented. All we can say is, if you want to ensure the most reliable response for the iBeacons, you need to follow the specifications as stated.
