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Thanks to finding a couple of geocaches here in Istanbul, my geocaching "2D convex hull" (the smallest possible convex polygon that covers an area), which I wrote some code to draw last year, just expanded a little further to the East. 
I've got a lot of the world left still to encircle, but I'm slowly extending my reach...
(previous map, for comparison: https://danq.me/_q23u/2024/04/dans-geoing-hull-2024-04-03.webp)
#note #istanbul #geocaching #maps #geography
Via: 
https://danq.me/2025/03/25/geocaching-convex-hull-now-includes-turkey/
@dan do you take the farthest N, E, S, W coordinates to map this?
@vicarvernon Not quite. It's easiest perhaps to visualise a convex hull algorithm like this:
1. For the first three points, draw a triangle that connects them.
2. For each subsequent point:
- if it falls within the shape you've drawn - ignore it,
- if it doesn't, turn the nearest side of your shape into two sides, with a vertex at your new point
That's not actually the algorithm I use - I use one called the Monotone Chain (an explanation and my source code are at https://danq.me/2024/04/04/geo-limits/), illustrated in the attached animation. But the result is still the same: the smallest possible 2D shape that covers a set of points without any concave parts.