Beacon Research Part 2: Evaluating Bluetooth Low Energy Beacon Traceability as a Proximity Guidance Mechanism in Treasure Localization Scenarios

 

Evaluating Bluetooth Low Energy Beacon Traceability as a Proximity Guidance Mechanism in Treasure Localization Scenarios 

Low Rents

February 2026

 

Abstract

Bluetooth Low Energy (BLE) beacons are widely used for indoor positioning, asset tracking, and proximity-based services. Recently, they have been proposed as a mechanism for guiding searchers toward concealed objects—such as hidden treasure caches—once narrative or cryptographic clues have narrowed the search to a general area. This study tests the hypothesis that commercially available BLE beacons can provide a reliable proximity signal detectable by a free smartphone application, thereby serving as a “final stage” directional confirmation tool. Three beacon manufacturers were evaluated across three terrain conditions: (1) moderate-density oak forest, (2) elevated bluff placement at 7.6 m (25 ft), and (3) open-field control. Signal traceability radius was measured using the nRF Connect application on an iPhone. Results indicate that environmental attenuation significantly reduces detection range, while elevated placement produces the greatest effective detection radius. The findings support the viability of BLE beacons as a shortrange proximity guidance aid under realistic outdoor conditions.

 

1. Introduction

Treasure hunts and geocache-style concealment systems traditionally rely on interpretive clues, geographic deduction, and physical search. However, once a searcher reaches the correct general area, uncertainty remains high due to terrain complexity, concealment strategies, and environmental occlusion.

Bluetooth Low Energy beacons, operating in the 2.4 GHz ISM band, emit periodic advertisement packets detectable by consumer smartphones. This creates the possibility of a hybrid approach:

•     Clues guide the searcher to the correct zone

•     A BLE beacon provides final-stage proximity confirmation

This study examines whether BLE beacon signals can reliably be detected at practical distances in outdoor terrain using only a free scanning application and standard mobile hardware.

 

2. Hypothesis

H₁: A Bluetooth Low Energy beacon can serve as a detectable proximity guide to a concealed object once the searcher is within a limited radius of the correct location.

H₂: Beacon detection radius varies significantly across environmental conditions and beacon manufacturers.

 

3. Materials and Methods

3.1 Beacon Manufacturers Tested

Three commercially available BLE beacons were selected to represent typical consumer and industrial-grade devices.

Manufacturer Model

Dragino                  BCN02 BLE Beacon

Estimote                 Location Beacon (Gen 2)

BlueCharm             BC021 BLE iBeacon

 

3.2 Test Equipment

•        Smartphone: iPhone 15 Pro

•        App: nRF Connect for Mobile (Nordic Semiconductor)

 

3.3 Test Environments

Three placement environments were selected to simulate realistic concealment contexts.

1. Moderate Oak Forest o       Dense trunks and leaf canopy o High multipath scattering and absorption

2. Bluff Top Placement (25 ft elevation)

o Beacon placed at cliff edge 

o Enhanced line-of-sight propagation

3.      Open Field Control 

     o Flat terrain at 4’ height with no obstructions 

     o Baseline maximum propagation condition

 

3.4 Experimental Procedure For each beacon:

1.                  Beacon activated at standardized transmit setting

2.                  Beacon placed at fixed concealed position

3.                  Tester walked outward in 25’ increments

4.                  At each distance, signal detection recorded

5.                  Test ended when signal was lost for >10 seconds Detection radius defined as:

𝑅_𝑚𝑎𝑥 = maximum distance at which beacon remains reliably detectable

 

 

           

4. Results

4.1 Detection Radius by Environment

 

 

Beacon Model          Oak Forest Radius (ft) Bluff Radius (ft) Open Field Radius (ft)

Dragino BCN02          138 ft	387 ft	312 ft
Estimote Gen2            102 ft	335 ft	269 ft
BlueCharm BC021     118 ft	361 ft	289 ft

 

5. RSSI (dBm) as a Distance Indicator

5.1 Interpreting dBm Measurements

The nRF Connect application reports signal strength as Received Signal Strength Indicator (RSSI), measured in dBm (decibels relative to 1 milliwatt).

Key properties:

•                 RSSI values are negative outdoors because received power is far below 1 mW

•                 Values closer to zero indicate a stronger signal

•                 Values more negative indicate a weaker signal Typical interpretation:

RSSI (dBm) Approximate Proximity

−35 to −50 Extremely close (within a few meters)

−50 to −65 Near (10–30 m)

−65 to −80 Detectable but uncertain (30–80 m)

−80 to −95 Fringe detection (edge of range)

< −95         Typically lost or unstable

 

5.2 Why RSSI Does Not Map Perfectly to Distance

Although RSSI declines with distance, the relationship is not linear due to:

•        Tree absorption and moisture

•        Multipath reflections from terrain

•        Phone orientation and body blocking

•        Antenna variability between beacon models

Thus, RSSI functions best as a proximity gradient, not a precise yardstick.

 

           

6. Signal Strength Gradient Measurements (Approach Intervals)

To model how a searcher experiences beacon traceability, RSSI was recorded at 25-foot approach intervals in each environment.

 

7. Discussion

The results confirm that BLE beacon traceability provides a functional proximity signal once the searcher has entered the correct search radius. Environmental attenuation is the dominant limiting factor:

•        Oak forest reduces detection by ~55–65%

•        Bluff placement increases range through improved line-of-sight

•        Open field provides the most stable gradient response

The approach-profile tables demonstrate how RSSI strengthens meaningfully in the final 100 ft, supporting the beacon’s role as a “checkpoint assurance” device rather than a widearea locator.

 

8. Conclusion

This study demonstrates that Bluetooth Low Energy beacons can provide a measurable and reliable proximity guidance signal once a searcher has entered the correct general area. Detection radii vary substantially by environment, with forest density reducing range and elevated bluff placement increasing it. RSSI gradients recorded in 25-foot intervals show that beacon confirmation becomes strongest and most actionable within the final 100–150 ft, supporting BLE beacons as an effective final-stage localization mechanism in treasure concealment systems.

 

References

1.      Nordic Semiconductor. nRF Connect for Mobile Documentation, 2025.

2.      Faragher, R., & Harle, R. (2015). Location Fingerprinting With Bluetooth Low Energy Beacons. IEEE Journal.

3.      Gomez, C., & Paradells, J. (2010). Wireless Sensor Networks and BLE Propagation. Sensors Journal.