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Coastline Length Calculator

Use our interactive map to automatically detect coastlines in any region or manually draw any path to accurately calculate its length in kilometers and miles.

How It Works

Auto Mode: Detect Coastline

  1. Navigate and zoom into a coastal area on the map (Zoom level 10+ is required).
  2. Click the "Detect Coastline" button to fetch all coastline data in the current view.
  3. Use the "Detail Level" slider to adjust the precision of the coastline measurement.
  4. Use the eraser tool to remove any unwanted lines for a precise calculation.

Manual Mode: Draw & Measure

  1. Switch to "Manual Mode" on the control panel.
  2. Click the "Draw" button to activate the drawing tool.
  3. Click on the map to start drawing your line or path. Double-click to finish.
  4. Your line's total length will be calculated and displayed instantly.

Understanding the Coastline Paradox

The coastline paradox is the observation that a coastline does not have a well-defined length. The measured length depends on the scale of measurement. As you use a smaller unit of measurement (like a smaller ruler), the measured length increases because you capture more intricate details like small bays and inlets.

This tool's "Auto Mode" demonstrates this concept perfectly. When you adjust the "Detail Level" slider, you are effectively changing the "ruler" used to simplify the coastline data. A higher detail level (a smaller ruler) results in a longer calculated length, while a lower detail level smooths out the line, resulting in a shorter length.

Frequently Asked Questions

What data source is used for auto-detection?

The automatic coastline detection uses real-time data from the OpenStreetMap (OSM) project via the Overpass API. Its accuracy depends on the quality of OSM data for that specific region.

Can I export the lines I have drawn or detected?

Yes. Once a coastline is on the map, an export button will appear above the length display. You can download the data as a standard GeoJSON file for use in other GIS applications.

Is this tool free to use?

Yes, this tool is completely free for all users. It is designed for educational purposes, hobbyists, and anyone with a curiosity for geography.