🧲
Magnetometer
Heading reference
Provides absolute heading (north/south) via geomagnetic field. Corrects gyro drift.
UPDATED · 2026-05-06
🗺 Space Scan · Indoor Mapping (FREE)
Walk through unknown space (cave, basement, tunnel) and the app auto-maps your path, detects anomalies, and shows your way back — WITHOUT GPS and WITHOUT charging tokens. 100% local (passive WiFi/BT scan + IMU dead-reckoning).
📡
No GPS Needed
Pure PDR with magnetometer + accelerometer + gyroscope fusion. Works underground.
⏺
One-tap REC
Tap ⏺ button in Room Scanner. Everything auto-saves as a "Survey".
🧭
Back to Entrance
Reverse PDR path with arrow + distance counter. Never get lost.
How the scan works
Top-down view of an underground space with walls + hidden anomalies. Tap ⏺ REC and watch the PDR walk record the path + reveal METAL/VOID anomalies as you walk.
Status IDLE
Path Length 0 m
Anomaly Pins 0
Duration 00:00
You (current position)
PDR path (1 Hz samples)
METAL anomaly
VOID anomaly
Breadcrumbs return arrow
How PDR works
PDR (Pedestrian Dead Reckoning) combines 3 phone sensors in real-time. Result: accurate mapping without GPS.
📐
Accelerometer
Step detection
Detects peak/trough on vertical axis (Az) with low-pass filter at 2 Hz. Each step = ~0.7m.
🌀
Gyroscope
Rotation rate
Integrates angular velocity to compute heading change. Drift fused with magnetometer.
🛰
GPS (if available)
Outdoor anchor
When outdoor and signal available, GPS becomes absolute reference for PDR path. Underground: GPS = NaN, PDR only.
4 Recording steps
01
⏺
Start Recording
In Room Scanner, tap ⏺ red button top-right. Pulsing red dot + live banner shows name/time/samples/pins.
02
🚶
Walk & Scan
PDR captures position/heading/velocity every 1 sec. AI findings from AR Scanner auto-pin with verdict + depth + confidence.
03
🎤
Voice Annotations
Long-press 🎤 button → speak (up to 30s) → auto-transcription → auto-pin in Survey as anomaly with your voice description.
04
💾
Auto-Save
Stop recording → Survey saved with id, name, duration, path, pins, notes. Available in 📋 Surveys list.
Real-world applications
🪨
Speleology
Cave mapping with topology, metal deposit detection, return-to-light navigation.
🏺
Underground Archaeology
Recording of crypts, Byzantine corridors, Roman cisterns. With GPS lat/lon when available.
🎯
Tactical Indoor Ops
Mapping clearing operations in unknown indoor space. Breadcrumbs for quick exit.
⛏
Mining Tunnels
Safe exploration of abandoned mine shafts. Anomaly detection for metals/voids.
🚑
Disaster Response
Search & rescue in damaged buildings without power/signal. PDR + breadcrumbs saves lives.
🔧
Utilities Survey
Mapping basement infrastructure (cables, pipes) with depth/position annotations.
Algorithms
PDR Algorithm
Pedestrian Dead Reckoning fusion with 3 sensors. Step detection at 2 Hz, heading drift correction per step, position update at 1 Hz.
step_detection: peak/trough on Az with low-pass 2 Hz
heading: gyro integration + magnetometer correction
position: dead-reckoning at 1 Hz, x/y in meters
Multi-Survey Merge (ICP)
Iterative Closest Point algorithm to combine multiple Surveys in same space. Auto-aligns with translation+rotation.
SessionMerger.icp(survey_a, survey_b) → translation+rotation
Treasure Probability (KDE)
Kernel Density Estimation over all anomaly pins → probability heatmap for aggregate hot-spots.
TreasureProbabilityAI.kdeMap(pins, σ=2m) → heatmap