# Features Research

**Domain:** Maritime Ship's Logbook PWA
**Researched:** 2026-05-26
**Confidence:** HIGH

## Feature Categories

### 1. Vessel & Crew Master Data (Stammdaten)
- **Vessel Profile**: Capture Yachtname, Heimathafen, Charterfirma, Eigner, Kennzeichen/Zulassungsnummer, Funk-Rufzeichen, ATIS-Nr, MMSI-Nr.
- **Crew Registry**: Skipper and crew profiles (up to 6 members) with Name, Anschrift, Geburtstag, Tel-Nr, Nationalität, Pass-Nr, Blutgruppe, Allergien, Krankheiten.
- **Deviation Table (Steuertafel)**: Standard magnetic compass deviation table mapping Compass Heading (MgK) from 000° to 360° (in 10° increments) to Deviation (Ablenkung).

### 2. Journey Logbook (Logbucheintrag)
- **General Journey Info**: Date, Day of Travel (. Reisetag), Departure (Reise von) & Destination (nach).
- **Hourly/Event Entry**: Time, Compass Course (MgK), Chart Course (rwK/KüG), Wind (pressure hPa, direction, strength), Sea State (Seegang), Weather (icons/symbols), Current (Strom), Heel (Lage), Sail Configuration (G, F, S, StF) or Motor run hours, Log reading, Distance, and GPS Coordinate with custom remarks.
- **Daily Summaries**: Position morning & evening, freshwater/fuel stock checks (morning stock, refilled, evening stock, daily consumption).
- **Sign-off**: Signatures of Skipper and Crew (names in block letters + signature).

### 3. Smart Integrations (Assistance)
- **OpenWeatherMap Integration**: Automatically query and pre-fill wind direction/strength, pressure, and weather state based on geographical coordinates.
- **GPS Coordinates Capture**: Fetch current latitude/longitude via device GPS and pre-fill coordinates into log entries.

### 4. Data Management, Auth & Cryptography
- **Passkey Accounts (WebAuthn)**: Passwordless user registration and login using device authenticators (biometrics, secure keys).
- **Client-Side E2E Cryptography**: Transparent client-side AES-GCM-256 encryption. WebAuthn PRF and BIP39 recovery word helpers for zero-knowledge key derivation.
- **Multi-Logbook Manager**: Dashboard interface allowing skippers to create and switch between multiple ship logbooks under one account.
- **Offline-First Synchronization**: Sync local changes (IndexedDB cache) to remote PostgreSQL via transaction logs and delta packet exchanges, offering conflict resolution markers.
- **CSV Data Export**: Generate and download unencrypted CSV logbooks compiled on-the-fly client-side (after decrypting entries), or trigger local email/message sharing.
- **Offline Assets & Service Worker**: Cache all HTML, JS, CSS, and assets so the application runs completely disconnected.

## Feature Scoping: Table Stakes vs Differentiators

| Feature | Category | Type | Complexity | Notes |
|---------|----------|------|------------|-------|
| Vessel Profile | Stammdaten | Table Stake | Low | Form entry with validation. |
| Crew Registry | Stammdaten | Table Stake | Low | Up to 6 profiles, standard fields. |
| Logbook Form | Logbuch | Table Stake | Medium | Complex form containing wind, course, and sails. |
| Deviation Table | Stammdaten | Table Stake | Low | Grid mapping MgK to Abl. |
| CSV Export | Data | Table Stake | Medium | Client-side decryption and CSV download trigger. |
| Passkey Auth | Auth | Table Stake | Medium | WebAuthn biometrics setup (SimpleWebAuthn). |
| E2E Cryptography | Crypto | Table Stake | High | Web Crypto API, PRF derivation & recovery fallback. |
| Sync Manager | Data | Table Stake | High | Local queue processing, background pushes, conflict management. |
| Multi-Logbook UI | UI | Table Stake | Medium | Dashboard to create, delete, and switch logbooks. |
| Offline PWA | System | Table Stake | Medium | Service Worker configuration. |
| GPS Fetching | Assistance | Differentiator | Low | HTML5 Geolocation API integration. |
| OpenWeather API | Assistance | Differentiator | Medium | Needs API key, coordinates, and fallback for offline. |
| Adaptive OS UI | UI/UX | Differentiator | High | Modifying UI based on UserAgent/OS detection. |

## Anti-Features (Do Not Build)

- **Cleartext Server-Side Storage / Sync**: The server must never store unencrypted vessel, crew, deviation, or journal entry data.
- **Classic Username / Password Login**: Passwords introduce security risks and weak encryption bases. Enforce biometric/hardware Passkeys (WebAuthn) instead.
- **Server-Side Data Analytics**: The backend has zero visibility into user logs, avoiding tracking.

## Dependencies & Risk Analysis

1. **Weather API Dependency**: OpenWeatherMap API requires internet access. If the user is offline (common at sea), the API will fail. 
   - *Risk Mitigation*: Implement clean offline fallback. Inform the user they are offline and allow manual weather entry.
2. **GPS Geolocation Dependency**: Requires browser permissions. Device GPS can be slow to lock or unavailable on some tablets without GPS chips.
   - *Risk Mitigation*: Allow manual entry of latitude and longitude as fallback.
3. **PWA Storage Cleared by OS**: iOS Safari sometimes purges IndexedDB for apps not added to the home screen if they are unused for 7+ days.
   - *Risk Mitigation*: Display a warning prompting the user to install the app to the home screen (PWA installation protects storage) and encourage regular backups using the CSV export.

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*Features research for: Kapteins Daagbox PWA*
*Researched: 2026-05-26*