Map Area Tool

Measure the area of rooftops and regions from Google Maps screenshots.

Setup

pip install -r requirements.txt

Run

# Open with file dialog
python main.py

# Open a specific image directly
python main.py /path/to/screenshot.png

How to Use

Step 1 — Calibrate the Scale

Google Maps always shows a scale bar at the bottom-left of the map.

1. Press R (or click "Measure Scale Bar")
2. Click the left end of the scale bar in your screenshot
3. Click the right end of the scale bar
4. In the sidebar, enter the real distance shown on that scale bar (e.g. 50 for "50 m")

Step 2 — Draw Your Polygon

1. Press P (or click "Draw Polygon")
2. Click around the edges of the roof/region
3. Press Enter or double-click to close — or click near the first point (it snaps)

Step 3 — Read Results

Area, bounding box dimensions, and perimeter are shown in the sidebar. Switch units (m², ft², yd², km², acre) from the dropdown.

Step 4 — Export (optional)

Press Ctrl+E or click "Export Results" to save as JSON, CSV, or TXT.

Shortcuts

Key	Action
P	Polygon mode
R	Ruler mode
Enter	Close polygon
Ctrl+Z	Undo last point
Esc	Clear all
Scroll	Zoom in/out
Middle drag	Pan
Ctrl+O	Open image
Ctrl+E	Export results

Accuracy

Accuracy depends on how precisely you measure the scale bar. Zoom in on the scale bar before measuring for best results. The tool uses the Shoelace formula for polygon area calculation.

Project Structure

map_area_tool/
├── main.py           # Entry point
├── requirements.txt
└── app/
    ├── canvas.py     # Interactive image canvas (drawing, zoom, pan)
    ├── geometry.py   # Area/perimeter math + unit conversions
    ├── panels.py     # Sidebar UI panels
    └── window.py     # Main window, wires everything together