AI and programming classes in Aylesbury

OpenStreetMap stores the boundary of Aylesbury Town Council, tagged as a civil parish, as 18 separate lines. The learner joins them end to end into one closed shape with 1,584 corner points, and works out its area with the shoelace formula: 14.01 square kilometres. Then the map data for the surrounding rectangle comes down in twelve tiles, because the full rectangle is too big for one request, giving 1,405 places tagged as a shop or an amenity. In OpenStreetMap "amenity" covers far more than cafés: the commonest are car parks, benches, bins and post boxes.

Ray casting works like this: from the point, imagine a line running off to the right, and count how many times it crosses the boundary. An odd number means inside, even means outside. A second method, the winding number, adds up how many times the boundary wraps around the point. On all 1,394 places in the rectangle the two methods agree exactly, which is a good sign that both are coded correctly.

Three lessons stand out. First, the tempting shortcut of checking only the surrounding rectangle is wrong for 195 of the 1,394 places, about one in seven, because the parish fills only 55.4% of its rectangle. The rectangle is still useful as a quick first filter, just never as the answer. Second, ray casting has a famous bug. If the imaginary line passes exactly through a corner, a careless version counts that corner twice, once for each side that meets there. The learner builds that careless version and tests points placed exactly level with each corner: it gives the wrong answer for 1,401 of 1,583 of them. Real data rarely lines up so exactly, which is how such a bug can go unnoticed. Third, eight places sit within 10 m of the line, close enough that small errors in the mapped boundary could flip the answer.

Finally, the same code settles a local puzzle. Testing the reference point for each recorded suburb shows Walton Court, Bedgrove, Southcourt, Quarrendon, Elmhurst and Haydon Hill inside the Town Council area, but Watermead, Berryfields and Kingsbrook outside it, along with the villages of Stoke Mandeville and Bierton. Many people would call all of those "Aylesbury"; the Town Council boundary does not. Neither answer is wrong. They are different definitions, and any program has to pick one on purpose.

An Aylesbury teenager who can test geometry code properly will use AI with real judgement, one of the strongest reasons to learn to code in 2026. The longer argument is in why teenagers should still learn to code in 2026.