This article gives common guidelines for beacon placement, the first and most important step of new map design.
We provide detailed instructions and address frequent questions at the end of this article. Guidelines in this article apply to all common locations, for any specific issues and problems, please contact the support.
Technological fact: common WiFi /Beacon positioning services are based on RSSI measurements, that just allow to estimate distances, not direction.
Due to the fact that direction information is unavailable, to build accurate positioning services, we need to put some effort in beacon placement. Please, follow the instructions in this guide to achieve stable and accurate positioning.
First we define the area of interest - the part of location where we need navigation.
For example, we may need to navigate up to some room, but not inside it. Or we need to understand our position inside some exact rooms, corridors, stairways, etc. We equally distribute beacons over the area of interest (draw beacons expected location on map).
The figure below shows the example of beacon placement over the location.
Because of signal propagation properties, the calculated positions tend to be inside the convex hull of all visible transmitters at the moment. We highlighted the area that the user position will be likely projected into.
The user's position will be likely fit into the green region, because there are no signals coming from the outside of beacons placement. To overcome this geometrical restriction, we suggest the following steps for beacon placement. The algorithm helps to achieve a better location coverage, and thus get more stable and accurate positioning.
Figure 1 shows the example of the location plan. The room on the bottom side of the map is expected to appear in navigation, that’s why we plan to put the beacon there. Other rooms with no beacons inside will be blocked from entering
The rule of thumb for beacon placement is that each room will require 1 beacon at least. For larger rooms, more beacons might be needed.
We cannot localize inside the room if we have no beacons visible. We can enter and leave the room using dead reckoning, but no stable positioning is possible outside the convex hull of beacon positions.
Create a new location and upload your map. Follow the instruction for sublocations management.
We add the raw image to client:
Barriers are objects that prevent motion through it. We draw all static objects inside the location area as barriers (walls, tables, etc.). This step will prevent navigation from entering unexpected points, and moving through objects walls, etc.
The outer side of the map should also be drawn as a barrier (5-10 m wide to fully cover the outer border of the image).
For sublocation plan (Figure 1), we add barriers (Figure 4).
Rooms where no navigation is expected (no visible beacons inside) should be removed from the navigation area and covered with barriers.
Outside of this area there is no information and thus we can’t perform localization with the same accuracy.
We put barriers in areas where no beacons are placed and where no navigation is intended, barriers allow us to fully ignore and avoid some specific location during navigation.
There are two optional usage types for beacons depending on its visible range: work for the specific area (room, stairway, elevator) or cover as much area as possible.
The visible area of the beacon is controlled by its installation type (wall / ceiling, room / corridor, pointed to corridor or pointed to the room).
Combine both types of installation depending on its purpose:
Beacons should be placed with a 7-20m interval depending on the area importance and geometry. 7-10m interval in corridors. In halls and huge open spaces it's preferable to place beacons on the ceiling or use other types of positioning devices (locators, etc.).
Try to achieve equal and wide beacons distribution with room angles covered where possible:
Consider using the lattice pattern with emphasis on room corners as shown at figure below:
Figure 5 demonstrates the optimal settlement of beacons for several types of room geometry.
As the best navigation quality could be achieved inside the green area (the convex hull of beacons), to have a larger coverage area we need to put beacons wider (closer to borders and corners).
For better visibility we need to put sensors in the center of the halls.
For large locations (halls, conference rooms), beacons should be evenly distributed with emphasis on borders and corners of the location.
Placement on outer walls increases, thus increasing the navigation area.
Placing sensors on the ceiling in the center of corridors does not give us information about which side of the corridor the user walks, but this configuration has a good coverage overall.
If possible, try putting the beacons on the opposite sides of the corridor to increase the positioning accuracy. Check figure 3 for example.
As usually the number of beacons is limited, we start beacon placement from corridors and intersections. Increasing the beacon visible range increases the total coverage, so try to find the optimal place and direction for each beacon.
We evaluate on our current beacons placement:
To achieve better location coverage, we should distribute the beacons wider with emphasis on corners and walls.
Correct placement is presented on a figure above.
Criteria for a correct placements:
Point move through walls, enter the rooms nearby unexpectedly
Increase the nearby walls thickness up to 0.5-1m where possible, this will prevent the point from jumping into the room. If the room is not important for navigation, we can cover the whole room with a barrier - preferable.
Point is moving through walls
Huge mean position error
Point is shown on another part of the map
There might be several possible reasons:
Position shifted to the center of the map
Position never reach the outer wall, position is shifted to the closest beacons
Check beacon placement, try to install the beacons to cover the most possible area.