This dApp allows you to enter your graphical coordinates and search for interesting neighbors.
My original idea was to split the Earth into quadrants, each split into four subquadrants and associate coordinates with them. But it failed due to not enough gas.
So I just split the Earth into a lattice of quadrants (one level).
In the current version the split is imperfect, as the Earth is not square as I assume. See also TODO.md.
So, the program can do its task, but does it imperfectly. It is a prototype for further evolution.