Measure the road outside your school.

Ask first

• Tell the head of your school what you will film, and when.
• Pick the busiest time: when school ends is best.

Mark the road

• With the tape measure, mark a rectangle on the road, for example 8 m long and 7 m wide.
• Put a bright marker at each of its 4 corners. Anything works if the camera can see it clearly from above: A4 paper, a chalk mark, a bright cloth, a small cone.
• Put 4 more markers: two lines across the road, A and B, exactly 15 m apart, one marker on each kerb. This is the check line: the tool never uses it to measure, so it can prove itself later.

📝 Open the field sheet

Print this sheet and write each number on it while you measure.

Film from high up

• Go somewhere high that looks down on the crossing: a bridge, a roof or a first-floor window.
• Hold the phone sideways (landscape), at normal zoom. Keep it still.
• Film for 10 to 20 minutes while people cross. All 4 corner markers must stay in view.

Mark the road in the app

• Take one picture (frame) from your video:

Copyffmpeg -ss 5 -i YOUR-VIDEO.mp4 -frames:v 1 frame.jpg

• Open App, step 1. Load frame.jpg.
• Click the 4 corner markers on the road, going round in one direction. Type the sizes you measured (8 and 7). Then click A near, B near, B far, A far, and type 15 in ‘Line A to line B’.
• Copy the text the page makes and save it as site.json.

Run it

• Get the code and put your key in a file called .env:

Copygit clone https://github.com/shaunmortal/crossing-watch
cd crossing-watch
echo "MODEL_API_KEY=your-key-here" > .env
python3 test_cw.py        # checks that everything works, under a minute

• First run it for free: it only checks your video and tells you the cost.

Copypython3 monday.py YOUR-VIDEO.mp4 site.json

• Then the real run, with a spending limit (here, 14 dollars):

Copypython3 monday.py YOUR-VIDEO.mp4 site.json --budget 14 --yes

Answer the agent's question

• The agent stops and asks you to measure the check line with the tape.
• Type what the tape says. Use the R number it printed:

Copypython3 agent.py YOUR-VIDEO.mp4 site.json --out out/YOUR-VIDEO-agent --answer R1 "15 m"

Read the report and send it

• Open out/YOUR-VIDEO/index.html: every near-miss with its blurred clip, the road map, the fix and the letter.
• Make the printable letter, then the head of the school reads it, signs and stamps it:

Copypython3 letter_pdf.py out/YOUR-VIDEO site.json

• Send it with the report to the road authority. In India you can also use the government's grievance portal, CPGRAMS.