React Native GPS Accuracy Checker

A React Native application designed to test GPS geolocation accuracy against established USGS benchmarks. This single-screen app compares GPS readings against a benchmark location and provides comprehensive statistical analysis of location accuracy.

🎯 Project Overview

Built to test GPS accuracy against known surveyed benchmarks from the National Geodetic Survey (NGS). Successfully tested on two benchmarks in Marin County, CA with real-world accuracy validation.

Key Features

Single GPS reading: Get one-time location reading
Continuous tracking: Watch position changes in real-time
Distance calculation: Haversine formula implementation for precise distance calculations
Statistical analysis: Real-time statistics including mean, standard deviation, min/max distances
Cross-platform support: Handles iOS and Android location permissions
User-friendly interface: Clean, responsive design with coordinate input and real-time display

🏗️ Architecture

Core Architecture

Single-file app structure: The entire app logic is contained in App.tsx
No navigation library: Single screen application with all functionality on one view
State management: Uses React hooks (useState, useEffect) for local state management
No external API dependencies: All processing is done client-side

Key Dependencies

@react-native-community/geolocation: Core geolocation functionality
react-native-permissions: Handles location permission requests across platforms
react-native-safe-area-context: Safe area handling for different device types

Technical Stack

Languages: JavaScript/TypeScript, JSX
Framework: React Native with CLI (not Expo - chosen for full native access to precise GPS APIs)
Native APIs: iOS Location Services, Core Location
Tools: Xcode, Metro, npm, CocoaPods
Libraries: @react-native-community/geolocation
Platforms: iOS development and deployment (Android ready)

🚀 Getting Started

Note: Make sure you have completed the React Native Environment Setup guide before proceeding.

Prerequisites

Node.js >= 18
React Native CLI
iOS: Xcode and CocoaPods
Android: Android Studio and SDK

Installation

Clone the repository

git clone <repository-url>
cd react-native-geolocation-tester

Install dependencies

npm install

iOS setup (required on first clone or after native dependency changes)

bundle install
bundle exec pod install

Running the App

Start Metro bundler

npm start

Run on your target platform

iOS

npm run ios
# OR for device deployment
npx react-native run-ios --device

Android

npm run android

If everything is set up correctly, you should see the GPS Accuracy Checker running on your device or simulator.

Development Tools

# Run linting
npm run lint

# Run tests
npm test

📱 How to Use

Set Benchmark Coordinates: Enter the latitude and longitude of your known benchmark location
Choose Reading Mode:
- Single Reading: Get one GPS reading to test accuracy
- Continuous Tracking: Start real-time tracking for statistical analysis
View Results: See distance from benchmark, GPS accuracy, and statistical analysis
Analyze Data: Review recent readings and comprehensive statistics

🔧 Configuration

Benchmark Location

The benchmark coordinates can be set in the app interface or modified in App.tsx:

const [benchmarkLat, setBenchmarkLat] = useState('37.936722');
const [benchmarkLon, setBenchmarkLon] = useState('-122.534278');

GPS Configuration

The app uses high-accuracy GPS settings:

enableHighAccuracy: true
timeout: 15000ms
maximumAge: 0 (no cached readings)
distanceFilter: 0 (get all position updates)

📊 Testing Methodology

The app implements a comprehensive GPS accuracy testing framework:

Distance Calculation: Uses the Haversine formula to calculate precise distances between GPS readings and the benchmark location
Statistical Analysis: Provides real-time statistics including mean, standard deviation, min/max distances
Accuracy Tracking: Records both the GPS-reported accuracy and actual distance from known location
Historical Data: Maintains reading history with timestamps for analysis

🛠️ Development Insights

React Native Concepts Learned

Project Setup: CLI vs Expo trade-offs for native API access
State Management: React hooks for location data and UI state
Native Integration: iOS/Android permission handling differences
Performance: Location tracking cleanup and battery considerations

Mobile Development Best Practices

Permissions: Platform-specific location permission requirements
Real Device Testing: GPS functionality requires physical devices
User Experience: Input validation, error handling, responsive design
Performance: Proper cleanup of location watchers

Mathematical Implementation

Haversine Formula: Great-circle distance calculations
Statistical Analysis: Real-time computation of accuracy metrics
Coordinate Systems: DMS to decimal degree conversion support

🔍 Troubleshooting

Location Permissions

If location readings fail, check that:

Location permissions are granted in device settings
Location services are enabled on the device/emulator
The app has been granted "precise location" access (iOS 14+)

Metro/Build Issues

Clear Metro cache: npx react-native start --reset-cache
Clean build: Delete node_modules and run npm install
iOS: Clean Xcode build folder and re-run bundle exec pod install

Common Issues

Permission errors: Handling location access denied scenarios
GPS errors: Timeout, accuracy, and availability issues
Certificate/signing issues: Resolving Xcode keychain and provisioning problems
Metro bundler troubleshooting: Understanding when to restart vs reload

🎯 Success Metrics

✅ Functional app deployed to physical iPhone
✅ Real-world validation tested against two NGS benchmarks
✅ Accurate measurements confirmed GPS readings vs survey data
✅ User-friendly interface with coordinate input and real-time display
✅ Professional development workflow established

🚀 Next Steps for Enhancement

Android deployment: Extend to Android platform
Maps integration: Add visual maps showing GPS readings
Data persistence: Save readings to device storage
Bluetooth/external GPS: Connect to external GPS receivers
Background processing: Continue tracking when app backgrounded
UI polish: Custom icons, animations, better styling
Testing: Unit tests, integration tests for location functionality
V2: Integrate with NGS API to get benchmark data and allow user to enter benchmark number and receive information
V3: Integrate with NGS API to create a map of the area and allow user to find benchmarks and test accuracy

📚 Learn More

To learn more about React Native and GPS development:

React Native Website - learn more about React Native
React Native Geolocation - GPS API documentation
National Geodetic Survey - Find survey benchmarks for testing
Haversine Formula - Distance calculation methodology

📄 License

This project is built with React Native using @react-native-community/cli.

Name		Name	Last commit message	Last commit date
Latest commit History 5 Commits
.bundle		.bundle
__tests__		__tests__
android		android
docs		docs
ios		ios
.eslintrc.js		.eslintrc.js
.gitignore		.gitignore
.prettierrc.js		.prettierrc.js
.watchmanconfig		.watchmanconfig
App.tsx		App.tsx
Gemfile		Gemfile
Gemfile.lock		Gemfile.lock
README.md		README.md
app.json		app.json
babel.config.js		babel.config.js
index.js		index.js
jest.config.js		jest.config.js
metro.config.js		metro.config.js
package-lock.json		package-lock.json
package.json		package.json
styles.js		styles.js
tsconfig.json		tsconfig.json

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