AirLog: Store-Level Indoor Life Logging Made Easy
Organizations: University of Georgia Athens, Georgia, USA · University College London London, United Kingdom · University of Toronto Mississauga Mississauga, Ontario, Canada · University of Pittsburgh Pittsburgh, Pennsylvania, USA
Abstract
This paper presents AirLog, a smartphone-based life journaling system that automatically reconstructs users' store visits in shopping malls and summarizes them into human-readable journals. Unlike conventional indoor localization systems, AirLog avoids labor-intensive radio-map construction and dedicated wireless localization infrastructure and algorithm calibrations. Instead, it repurposes two cues already available in commercial spaces: semantic information exposed by ambient Wi-Fi SSIDs and indoor directory images. AirLog converts directory images into spatial maps and fuses Wi-Fi semantic anchors with inertial dead reckoning to recover store-level trajectories, which are then summarized into journals by an LLM. Such store-level life logs can support applications such as personal memory recall, activity reflection, and automated diary generation without requiring users to manually record where they have been. We implement AirLog on commodity smartphones and evaluate it on both a large-scale public dataset and a self-collected dataset. The results demonstrate that AirLog substantially improves store-level region recovery, semantic matching, trajectory reconstruction, and journal quality over existing baselines. A human evaluation further shows that the generated journals are coherent and faithful to users' visits.
Figures & tables
| Method | Area F1 | Region Purity | Matched Label F1 |
|---|---|---|---|
| Color Filling | 0.277 | 0.510 | 0.523 |
| Su et al.-style Boundary Detection | 0.144 | 0.468 | 0.506 |
| SAM 3 | 0.037 | 0.306 | 0.155 |
| AirLog w/o semantic subagent | 0.705 | 0.767 | 0.734 |
| AirLog w/ semantic subagent | 0.705 | 0.767 | 0.814 |
| Model | Input | Calls | Tokens (I/O) | Time (s) | Label F1 |
|---|---|---|---|---|---|
| GPT-5.5 | Full map | 24/24 | 127.4k/137.0k | 1,984.0 | 0.734 |
| GPT-4o | Region crop | 1,920/1,927 | 524.2k/24.6k | 1,815.9 | 0.814 |
| Method | Hall. Rate | chrF | BERTScore | ||
|---|---|---|---|---|---|
| P | R | F1 | |||
| SenLLM | 0.667 | 0.331 | 0.263 | 0.403 | 0.330 |
| AutoLife | 0.636 | 0.381 | 0.363 | 0.458 | 0.409 |
| AirLog | 0.000 | 0.420 | 0.485 | 0.529 | 0.506 |
| Module | Input | Output | Cost (USD) | Calls |
|---|---|---|---|---|
| Spatial description | 22.3k | 1.2k | 6.8 /hr | 1 per floor |
| Wi-Fi semantic agent | 118.7k | 13.2k | 4.3 /hr | |
| Trajectory validation | 62.8k | 26.9k | 4.3 /hr | 1 per session |
| Behavior inference | 1.9k | 0.8k | 1.3 /hr | 1 per session |
| Journal generation | 3.0k | 1.3k | 2.1 /hr | 1 per session |
| Total per session | 208.7k | 43.4k | 9.6 /hr | All modules |
Appendix figures & tables13 assets
Supplementary material from the paper’s appendix.
Appendix
| Method | Region [email protected] | [email protected] |
|---|---|---|
| Color Filling | 0.229 | 0.199 |
| Boundary Detection / Su et al. | 0.095 | 0.075 |
| SAM 3 | 0.020 | 0.016 |
| AirLog | 0.590 | 0.475 |
| Metric | Hong Kong | Beijing | Shanghai | Shenzhen | Dalian | Nanjing | Total |
|---|---|---|---|---|---|---|---|
| Active hours (h) | 59.3 | 5.8 | 208.4 | 225.5 | 2.6 | 101.3 | 603.0 |
| GPS points | 157,360 | 2,137 | 277,356 | 319,865 | 6,696 | 168,041 | 931,455 |
| Wi-Fi observations | 260,394 | 2,711 | 25,798 | 45,801 | 10,391 | 29,472 | 374,567 |
| Unique SSIDs (raw) | 21,303 | 984 | 1,730 | 2,125 | 1,604 | 1,274 | 29,020 |
| Unique BSSIDs (raw) | 56,615 | 1,742 | 2,541 | 3,199 | 2,832 | 1,922 | 68,851 |
| Avg. SSIDs per scan | 81.0 | 46.7 | 3.0 | 5.9 | 48.8 | 6.2 | 59.4 |
| Range | Cosine (Char) | Cosine (Word) | Cosine (TF-IDF) |
|---|---|---|---|
| 0.0 | 9,731 | 184,841 | 184,871 |
| 0.0–0.2 | 33,454 | 3 | 3 |
| 0.2–0.4 | 72,318 | 131 | 65 |
| 0.4–0.6 | 54,474 | 137 (34.3%) | 100 (9.0%) |
| 0.6–0.8 | 14,516 | 17 (58.8%) | 61 (44.3%) |
| 0.8–1.0 | 647 (52.2%) | 11 (100%) | 40 (90.0%) |
| Wi-Fi SSID | POI | Best Sim. |
| SKH-SchoolDevice | SKH Holy Carpenter Church | 0.693 |
| Beauty | A Boutea | 0.833 |
| MNSGUEST | Monster Sushi | 0.820 |
| a SKH-SchoolDevice : SKH is a dominant institutional prefix of the Hong Kong Sheng Kung Hui; “SchoolDevice” identifies a campus device network, pointing to an affiliated lodging facility rather than the church itself. | ||
| b Beauty : “A Boutea” is a beverage brand whose name superficially resembles “Beauty” in spelling; the SSID more plausibly belongs to a cosmetics or personal-care venue. | ||
| c MNSGUEST : MNS follows a typical three-letter property code convention; combined with its location in the Miramar cluster in Tsim Sha Tsui, the network is better attributed to Miramar Shopping Centre’s guest Wi-Fi than to a restaurant abbreviation. | ||
Trajectory Inference
Trajectory inference reconstructs continuous paths and underlying dynamics from sparse, noisy, or incomplete observations.
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