Tide Table Generator

A Python tool for generating printable hourly tide tables from daily tide prediction data. Converts CSV tide extrema to interpolated hourly values and produces professional PDF tables.

Features

• 📊 Converts tide prediction data from CSV format (daily high/low tide times) to hourly interpolated values
• 📄 Generates printable PDFs formatted for A4 paper with professional layout
• 🌊 Half-sine interpolation between tide extrema for accurate hourly predictions
• ✅ Data validation to ensure tide levels are within reasonable ranges
• 📅 Auto-detects time period - handles single month or multi-month data automatically
• 🖨️ Print-ready format optimized for easy reading

Requirements

pip install reportlab

Python 3.6+ required (uses standard library for other dependencies)

Quick Start

1. Install dependencies

pip install -r requirements.txt

2. Prepare your CSV file

Create a CSV file with tide prediction data:

Date,Time1,Height1,Time2,Height2,Time3,Height3,Time4,Height4
EXAMPLE-2025-12-01,0545,2.1,1215,0.7,1830,2.8,,
EXAMPLE-2025-12-02,0015,0.6,0630,2.2,1300,0.8,1915,2.7
2025-12-01,0107,1.1,0746,2.7,1400,1.1,2018,2.6
2025-12-02,0213,1.2,0826,2.8,1452,0.8,2128,2.7

Format details:

• Date: YYYY-MM-DD format
• Time1-4: High/low tide times in HHMM format (e.g., 0545 = 05:45)
• Height1-4: Tide heights in meters
• Example rows (starting with "EXAMPLE-") are ignored
• Empty columns for days with fewer than 4 tide extrema

3. Convert to hourly JSON

python convert_tide_data.py your_data.csv tide_data.json

This will:

• Read your CSV file
• Interpolate hourly tide levels using half-sine curves
• Validate the data
• Output JSON with 24 hourly values per day

4. Generate PDF

python generate_tide_pdf.py tide_data.json tide_table.pdf

Or specify a custom location:

python generate_tide_pdf.py tide_data.json tide_table.pdf "SENTOSA ISLAND"

This creates a print-ready PDF with:

• One month per page (portrait A4 layout)
• Day rows and hourly columns (00-23)
• Professional formatting optimized for readability
• Automatic detection of single or multi-month data

How It Works

1. CSV Parsing

The converter reads daily tide extrema (high and low tides) from your CSV file.

2. Half-Sine Interpolation

Between consecutive tide extrema, the tool uses half-sine interpolation to estimate hourly tide levels:

s = 0.5 * (1 + sin(π * x - π / 2))
height = h0 + (h1 - h0) * s

Where:

• x is the position between extrema (0 to 1)
• h0 is the height at the previous extremum
• h1 is the height at the next extremum
• s is the interpolation factor

This method provides smooth, realistic tide curves between known high and low points.

3. Validation

The tool validates:

• All 24 hours are present for each day
• Tide levels are within reasonable range (-0.5m to 4m)
• Data continuity across days

4. PDF Generation

Uses ReportLab to create professional tables with:

• Compact font sizing (6-6.5pt) to fit all data on one page
• Grid lines and section separators for readability
• Minimal margins to maximize data density
• Automatic pagination for multi-month datasets

Example Output

The generated PDF includes:

• Header: Location name and month/year
• Table: Day numbers (rows) × Hours 00-23 (columns)
• Footer: Data source information

Single month data generates 1 page. Multi-month data generates 1 page per month.

Data Sources

This tool works with tide prediction data from official sources such as:

• National hydrographic offices
• Port authorities
• Maritime and Port Authority of Singapore (MPA)
• NOAA (US)
• UK Hydrographic Office

Note: Always use official tide predictions for operational planning. This tool is for formatting and presentation only.

File Structure

tide-table-generator/
├── README.md                  # This file
├── convert_tide_data.py       # CSV to JSON converter
├── generate_tide_pdf.py       # JSON to PDF generator
├── template_example.csv       # Sample CSV format
├── requirements.txt           # Python dependencies
└── .gitignore                # Git ignore rules

Command Line Arguments

convert_tide_data.py

python convert_tide_data.py <input.csv> <output.json>

generate_tide_pdf.py

python generate_tide_pdf.py <input.json> <output.pdf> [location]

• location is optional (default: "TANJONG PAGAR")

Tips

• Use consistent date formats (YYYY-MM-DD) in your CSV
• Include example rows at the top of your CSV for reference
• Tide times should be in 24-hour HHMM format (e.g., 1430 not 2:30 PM)
• The tool automatically handles missing tide extrema (days with 2-4 tides)
• Output PDFs are optimized for A4 paper size

License

MIT License - Free to use for personal and commercial purposes.

Contributing

Contributions welcome! Feel free to:

• Report bugs
• Suggest features
• Submit pull requests
• Share your use cases

Author

Created for marine operations and coastal management workflows.

Acknowledgments

• ReportLab library for PDF generation
• Half-sine interpolation method commonly used in tidal analysis