PositionMe — Indoor Positioning System

An Android indoor positioning application developed for the University of Edinburgh's Embedded Wireless (EWireless) course, Assignment 2. The app fuses multiple sensor sources through a particle filter to provide real-time indoor navigation with metre-level accuracy.

Key Features

Positioning Fusion

• 500-particle SIR Particle Filter combining PDR, WiFi API, GNSS, and local calibration database
• Weighted K-Nearest Neighbours (WKNN) fingerprint matching against 395 collected reference points (K=10, floor-aware)
• 10-second initial calibration using multi-source weighted averaging (CalDB × 3.0, WiFi × 1.0, GNSS × 1.0)
• Adaptive heading bias correction with early-phase (15 steps, ±5°/step) and normal-phase (EMA α=0.10) modes
• ENU coordinate system (CoordinateTransform) for all fusion computations

Map Matching

• Wall constraint enforcement via axis-aligned segments from Floorplan API GeoJSON data
• Stairs step reduction (×0.5 horizontal displacement) when inside stairs polygons
• Floor change spatial gating — transitions only allowed within 5m of stairs/lift areas
• Elevator vs stairs classification using barometric elevation change rate
• 3-second debounce on floor transitions to prevent jitter

Data Display

• Three trajectory paths: PDR (red), Fused (purple), Smooth (green, moving average window=40)
• Colour-coded observation markers: GNSS (cyan, last 3), WiFi (green, last 3), Fused (red, last 10)
• Estimated position marker (grey) showing forward-120° reference point weighted average
• WiFi signal quality indicator (3-bar, based on CalDB match quality)
• Compass and weather overlays
• Collapsible toolbar with 10 toggle switches and map style selector (Hybrid/Normal-Pink/Satellite)

Indoor Positioning Mode

• One-tap entry from home screen with auto building detection
• Auto trajectory naming, auto start location, auto recording
• Indoor-optimised defaults (compass, weather, smooth path, auto floor, navigating ON)
• forceSetBuilding() bypasses polygon detection for immediate indoor map loading

Recording & Upload

• Protobuf trajectory with IMU, PDR, WiFi, GNSS, BLE, barometer, and test points
• IMU timestamp rescaling for server frequency compliance (≥50Hz)
• Sensor info fields (max_range, frequency) included in protobuf
• Post-recording correction screen with trajectory review and map type toggle

Technical Details

• Target SDK: 35
• Min SDK: 28
• Language: Java 17
• Code Style: Google Java Style Guide
• Unit Tests: 32 JVM-based tests (JUnit 4)
• Debug Control: Compile-time BuildConstants.DEBUG flag eliminates all debug logging in release

Building

1. Clone the repository
2. Add your API keys to secrets.properties:

   MAPS_API_KEY=your_google_maps_key
   OPENPOSITIONING_API_KEY=your_openpositioning_key
   OPENPOSITIONING_MASTER_KEY=your_master_key
   

3. Open in Android Studio and sync Gradle
4. Build and run on a physical device (sensors required)

Architecture

See Programmers_Guide.md for detailed system architecture, data flow diagrams, and design decisions.