Draw Smooth Curves on Real Maps with MapLineDraw

September 20, 2025 · View on GitHub

MapLineDraw lets you sketch corridors of railway lines or roads on an interactive map using smooth spline curves, ready to share with others.

Whether you're a transit enthusiast, a city planner, or just someone who loves to visualize infrastructure, MapLineDraw is a free and open source web application designed to let you draw smooth curves on a map provided by OpenStreetMap.

example

What Is MapLineDraw?

MapLineDraw is a free, open source web application that lets you draw smooth spline curves directly on an interactive map (using OpenStreetMap tiles). The tool is ideal for:

  • Sketching railway lines, highways, race tracks, or other paths
  • Measuring real-world infrastructure curves
  • Visualizing concepts for future public transport
  • Sharing your ideas with others using simple, link-based projects

Typically line-drawing tools rely on connected straight segments. MapLineDraw uses cubic B-splines, which means it can represent curves with continuous curvature — an important feature in real-world rail or road design.

Key Features

The most important features of MapLineDraw are:

  • 🎯 Interactive Spline Drawing
    Click to place control points, drag them to adjust, and instantly see the resulting curve update in real time.

  • 🧩 Cubic B-splines (Degree 3)
    Smooth paths with continuous curvature.

  • 📏 Automatic Geometry Analysis
    The app calculates total curve length, minimum radius, and estimated maximum speed using typical comfort-based acceleration thresholds used in railway engineering.

  • 🔄 Open or Closed Curves
    Usable for both routes and loops — you can do track modeling, circular paths, and more.

  • 📝 Project Metadata
    Add a name, author, and description for your design ideas.

  • 📂 Download and Share
    Save your projects to a custom .json file, which includes all curve geometry and metadata. Or, use shareable URLs to send your project directly to others.

  • 🎨 Customizable Legends
    Color-coded curves, editable via the project JSON file to help clarify your visualizations.

Use Cases

Infrastructure design is no longer the exclusive domain of specialized, expensive CAD tools. With MapLineDraw, anyone can:

  • Draft hypothetical rail corridors across regions
  • Analyze existing road or rail curves for speed feasibility
  • Trace real-world routes for measurement or export
  • Sketch race track concepts, nature trails, or even fantasy transit systems

It's a tool built for hobbyists, students, planners, or open data advocates.

Export and Import

While MapLineDraw does not currently export GeoJSON or KML, it allows you to download your project in a custom JSON format. This includes:

  • Curve type (open or closed)
  • Degree of spline
  • Control point coordinates (lat/lon)
  • Project metadata and legend

Because the format is clean and structured, it's easy to convert into other formats using a simple script — or fork the project to add that feature.

Open Source

MapLineDraw is fully open source under the MIT license. You can:

Known Limitations

MapLineDraw is not a professional-grade design tool. Its goal is simplicity, accessibility, and visual clarity, not engineering validation.

  • No elevation (height) support (so no tunnels/bridges yet)
  • No mobile browser optimization (best used on desktop)
  • No built-in export to GIS formats (yet)

Conclusion

MapLineDraw provides a simple and free drawing tool for curves on a real map. Whether you're mapping out the next high-speed rail link or tracing an existing corridor for fun, it's a tool that helps ideas take shape — smoothly. Go to maplinedraw.com and start drawing.

If you like the tool or have suggestions how to improve it, feel free to contribute or open an issue on GitHub: https://github.com/patrsc/MapLineDraw.