Quick tutorial

Follow these steps to get measuring area quickly!

1. Upload an image or take one using your phone on the mobile site. Ensure it has either a ruler or rectangle with known edge lengths in frame.
2. Set the scale using either the Calibration Ruler or Correct Perspective tool.
3. Draw one or more polygons on the image using the Draw Polygon tool. Click anywhere with the tool selected to draw the next vertex.
4. Choose units and other display options, then share and export the image using the tools on the sidebar.

About

This project was created for NCEA Level 3 Computer Science and as a submission for NZQA Scholarship Technology.

Area is calculated through Gauss' shoelace formula. Perspective transformations are calculated through homography techniques and computational linear algebra. This project is built in Javascript with a Flask web server for the backend.

© planimeter.nz 2025

Video tutorial

Key bindings

• P – Create Polygon
• R – Toggle ruler tool
• T – Toggle perspective correction tool
• C – Erase All
• Enter – Close tool / complete current operation
• Backspace / Delete – Delete selected object
• Escape – Close tool
• Ctrl + O – Open file
• Ctrl + Z – Undo
• Ctrl + Y / Ctrl + Shift + Z – Redo