SunTrack - UV tracking

SunTrack — UV Protection Assistant

Overview

SunTrack is a full-featured UV (Ultraviolet) tracking iOS application that helps users understand current UV intensity, receive personalized sun protection advice, and track sun exposure time. The app uses an offline solar position algorithm to calculate UV index estimates — no third-party API keys required.

Features

Real-Time UV Dashboard

• Large circular UV gauge with dynamic color transitions (green → yellow → orange → red → purple)
• UV level classification: Low / Moderate / High / Very High / Extreme
• Safe exposure countdown based on your skin type
• Full-day UV forecast chart with hourly predictions
• Sunrise / sunset / solar noon times and sun elevation angle

Smart Sun Timer

• Start/stop exposure timer with automatic logging
• Real-time safety progress ring with color warnings
• Activity type selection (Commute, Sport, Beach, Hiking, etc.)
• SPF-adjusted safe time calculation
• Today's cumulative exposure summary

Exposure Log

• Calendar heatmap showing daily exposure intensity
• 7-day / 30-day exposure trends
• Activity type distribution chart
• Detailed log entries with UV dose tracking
• Swipe-to-delete record management

Protection Advice

• Personalized protection level based on UV index + skin type
• Dynamic recommendation checklist (sunscreen, sunglasses, hat, clothing, shade)
• Sunscreen reapply timer (configurable interval)
• UV health facts and educational cards

Settings

• Fitzpatrick skin type selection (Type I–VI) with visual color display
• Default SPF value configuration
• Sunscreen reapply interval setting
• Optional OpenUV API key for enhanced real-time data
• Data management (export / reset)

Technical Highlights

Offline UV Calculation Engine

Since Apple's WeatherKit requires iOS 16+, SunTrack implements a solar elevation angle algorithm for fully offline UV index estimation:

UV_estimated = 12.0 × sin(solar_elevation)^1.3 × altitude_factor × ozone_factor

Where:
  solar_elevation = f(latitude, longitude, date, time)  // Astronomical calculation
  altitude_factor = 1 + 0.06 × altitude_km
  ozone_factor ≈ 0.9 (global average)

Accuracy: ±1–2 UV index under clear-sky conditions.

Fitzpatrick Safe Exposure Formula

Personalized burn time calculation based on the internationally recognized Fitzpatrick scale:

Safe Time (minutes) = (200 × skin_multiplier) / (3 × UV_index)

Skin Multipliers:
  Type I   → 2.5   (Very fair, always burns)
  Type II  → 3.0   (Fair, burns easily)
  Type III → 4.0   (Medium, sometimes burns)
  Type IV  → 5.0   (Olive, rarely burns)
  Type V   → 8.0   (Brown, very rarely burns)
  Type VI  → 15.0  (Dark brown/black, never burns)