It’s the ability of the Crownstones to know where you are when carrying a smart device with you. Your smart device measures the Bluetooth Low Energy signals emitted by the Crownstones. This makes it possible for the Crownstones to react to your presence and proximity.
To enable indoor positioning the following is required:
Every Crownstone in the sphere broadcasts its unique identifier a certain number of times per second.
While walking around a room, your phone records how strong each Crownstone is “heard” in different places of the room. This is what we call the fingerprint of a room.
Every second your phone will make a list of all the Crownstones it senses in that second, and how loud it perceives them.
Based on what the smartphone sensed, the Crownstone system will find the room that most closely matches that.
Several factors should be considered when placing Crownstones. A brief explanation of some of these factors is mentioned below:
Absorbance of signals
The strength of the received signals gets reduced when the signals need to travel through other high density or conducting materials. For example, metal appliances that block and reflect wireless signals such as fridges, ovens, washing machines, dryers, etc. Increasing the number of Crownstones will diminish these effects.
Coverage
Placing the Crownstones behind ceiling lights is of great help to increase the area covered by the Crownstones and diminish the absorbance of the broadcasted signals. This translates into better performance of the indoor localization.
Areas vs Rooms
The indoor localization has difficulty with multiple areas (i.e. no wall is separating the areas) in the same room (i.e. a space delimited by walls). This is because the difference in the measured signal in these areas can be very small. Therefore, it is preferred to have walls in between so that the signal strength can be better differentiated.
Symmetry
For indoor positioning, Crownstones should not only be placed along a single axis because not enough information will be provided to identify in which room you are. For example, in the setting shown above, the Crownstones will have trouble identifying in which room you are because the strength of the signals at the intersection on the left is the same as on the right.
You sit on the couch and it is getting dark
The lights in the room where you are can be turned on automatically. Presence information is needed to avoid lights going on even if you are not there!
Go to bed with peace of mind
A small delay doesn’t matter when turning things off. The only thing that matters is that you no longer have to do it manually! No more rounds of checking if everything has turned off!
Neighboring rooms are also turned on
Some people don’t like to peer into or walk into a dark hallway or another room. If you turn on the lights in all neighboring rooms a small delay doesn’t matter.
Four Crownstones at home is the absolute minimum. The more Crownstones are present, the more information becomes available to know someone’s location. Since the Crownstones in other rooms also contribute to the positioning accuracy, two Crownstones per room is often sufficient. Depending on the house, if there are heavy reinforced concrete ceilings and walls, the signals won’t travel as far and you might need more Crownstones.
For a Crownstone to detect your presence it might take up to 10 seconds. For example, when walking along the hallway to get to another room, the lights in the hallway won’t automatically turn on. However, they will do it if you stay in the hallway for a longer time.
Crownstones detect that you leave the house after not hearing from you for 5 minutes. After that time, they will think that you have left home (the sphere). Once a room is no longer occupied by anyone, a five-minute grace period starts. The five-minute grace is to avoid turning lights (or devices) off and on when you are still at home, but there is a long delay when your smartphone advertises your location to the Crownstones.
To improve the quality of the training, we give the following recommendations:
It’s difficult to put a number (in meters) for this answer as the accuracy depends on several factors such as the number of Crownstones present, how the training was done, the presence of metal appliances or the presence of people, etc. A more detailed explanation of this topic can be found in this post.
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