The physical conditions shaping the result
Site mapping, in the context of a beacon or indoor-navigation deployment, is the process of translating a physical space into a working plan for radio signals. It is not the same as obtaining a floor plan from facilities management. A floor plan shows walls, doors and room labels. A site map for proximity technology shows where signals will travel, where they will weaken, and where they will overlap in ways that either help or hinder your system.
Signal planning sits alongside that map. It is the deliberate decision-making about which beacon identifiers go where, what transmit power and advertising interval each unit should use, and how the resulting zones will behave when the space is occupied by people, stock, and moving objects. The two tasks are inseparable: you cannot finalise a signal plan without walking the space, and you cannot produce a useful site map without understanding the signal behaviour you are trying to achieve.
The output of this stage is not a decorative diagram. It is a documented reference that an installer can follow, a maintenance team can update, and a troubleshooting process can rely on when something stops working correctly. Without it, every subsequent decision about quantity, placement and calibration becomes guesswork.
Why a floor plan alone is insufficient
CAD drawings and architectural plans represent the space as it was built. They rarely reflect current reality: temporary partitions, stacked merchandise, metal shelving units, glass display cases, and ceiling-mounted projectors or ventilation ducts. These objects alter Bluetooth Low Energy (BLE) propagation in ways that a two-dimensional line drawing cannot capture.
Equally, a floor plan tells you nothing about what is on the other side of a wall. A partition that looks thin on paper might contain a metal-lined lift shaft, a dense services riser, or a row of commercial freezers. Only a physical survey reveals these conditions.
The relationship to deployment objectives
Your deployment objectives, defined in the preceding stage, dictate what the signal plan must achieve. If the objective is to trigger a notification when a visitor enters a specific gallery, the plan must ensure that the corresponding beacon's signal reaches the entrance but does not reliably reach the adjacent corridor. If the objective is indoor wayfinding, the plan must guarantee that overlapping beacon signals allow a positioning engine to resolve a location, rather than creating ambiguous readings. The site map is where those abstract objectives meet the physical constraints of the building.
Test the complete receiver path
Conducting the physical survey
Walk the space during operating hours and again when it is empty. The difference is often significant. A retail floor packed with stock and shoppers presents a very different radio environment to the same space before opening. Note the position and material of every major obstruction: metal racking, glass partitions, reinforced concrete columns, water features, and stacked goods. Record ceiling height at multiple points, since suspended ceilings, mezzanine levels and atriums change how signals propagate vertically as well as horizontally.
Take photographs at each planned beacon location, looking up at the ceiling and down at the floor. These images become invaluable during installation and future maintenance, particularly when the person doing the work was not involved in the original survey.
Mapping signal behaviour
With a small set of test beacons, take RSSI readings at a grid of points across the space. The grid spacing depends on the accuracy your application requires: tighter grids for wayfinding, coarser grids for simple zone detection. Record the readings at phone height, since that is where the receiver will typically be, not at ceiling height where the beacon sits.
Plot the results on your floor plan. You will quickly see where signals attenuate unexpectedly and where they bleed through walls or around corners. This is the signal map. It does not need to be pretty, but it does need to be accurate enough to inform placement decisions.
Environment-specific factors
In retail environments, plan around fixture changes. If a shop refits its floor layout quarterly, the signal map must account for the fact that a beacon mounted above one display might later find itself above a different material. Consider mounting beacons on fixed elements such as ceiling grids or structural columns rather than on movable shelving.
In museums, the challenge is often dense exhibit cases, many of which are metal-framed or glass-fronted. A beacon intended to serve one exhibit may be blocked by a large case placed between it and the visitor path. The survey must include exhibit positions, not just room geometry.
At events and temporary venues, the site map is a snapshot of a configuration that may last only days. The priority here is speed of deployment and predictable behaviour in an untested space. Pre-configured beacon groups with standardised power settings, combined with a rapid on-site RSSI check, are more practical than a detailed per-beacon calibration that cannot be completed in the available setup window.
Documenting the plan
The final site map should record, for each planned beacon position: the physical location described in unambiguous terms (for example, "ceiling tile grid reference B-7, north-east corner, 2.4 metres above finished floor level"), the intended identifier, the chosen transmit power and advertising interval, the expected RSSI at the nearest zone boundary, and any access constraints such as height, locked doors or restricted hours. This document becomes the installation specification and, later, the maintenance reference.
Thresholds, uncertainty and recalibration
Assuming uniform propagation
The most frequent error is treating BLE signals as if they spread evenly in all directions like light from a bare bulb. In practice, the antenna pattern of a typical beacon is not perfectly omnidirectional, and the surrounding structure distorts the pattern further. A beacon mounted flush against a metal ceiling panel will radiate more strongly downward than upward or sideways. Two beacons of the same model, mounted in identical-looking positions on different sides of the same room, can produce measurably different RSSI values because of hidden services or structural differences behind the ceiling.
Surveying in the wrong conditions
Surveying an empty venue and then deploying for a crowded one introduces a systematic error. The human body is largely water, and water attenuates 2.4 GHz signals significantly. A reading of -65 dBm in an empty corridor may become -75 dBm or lower when the same space is occupied. If your zone boundaries rely on a narrow RSSI window, that shift matters. Where possible, take readings in conditions that match expected operating conditions, or at least note the difference and factor it into your boundary thresholds.
Ignoring existing RF interference
Before committing to a signal plan, scan the environment for existing 2.4 GHz activity. Wi-Fi access points, Bluetooth audio devices, microwave ovens in staff kitchens, and legacy wireless equipment all share the same spectrum. Interference does not always prevent beacons from working, but it increases variance in RSSI readings, which in turn reduces the reliability of zone detection and positioning. If interference is severe in a particular area, the plan may need to adjust beacon density or transmit power to compensate, or accept reduced performance in that zone.
Not planning for maintenance access
A beacon mounted in an ideal signal position is useless if facilities staff cannot reach it without specialist access equipment or if doing so disrupts operations. During the survey, check how each position would be reached for a battery replacement. If a scissor lift is required, note that in the plan. If the position is above a display that cannot be moved, reconsider the location. Maintenance access is not a secondary concern; it directly determines whether the deployment remains operational beyond its first battery cycle.
Key checks before finalising the plan
- Has every planned beacon position been physically visited and photographed?
- Have RSSI readings been taken at phone height, not just at ceiling level?
- Does the plan show where signals from adjacent beacons overlap, and is that overlap intentional?
- Have you recorded the materials and thickness of every wall or obstruction between a beacon and its intended zone?
- Have you scanned for existing 2.4 GHz interference at each planned position?
- Is every position reachable for battery replacement without disrupting normal operations?
- Does the plan distinguish between fixed and movable obstructions, and has the impact of moved obstructions been considered?
- Has the plan been reviewed by someone who will not be present during installation, to check that the location descriptions are unambiguous?
Once these checks are satisfied, the site map and signal plan provide a sufficiently reliable foundation for the next stage: estimating how many beacons the plan requires and what that means for the budget. Without this groundwork, any quantity estimate is an assumption rather than a calculation.
