This morning's prompt is 'spool of thread'.

I got started on random walking my quads last night. I have picked a random quad and we can start looking up information about neighbors by row and column.Which column in the adjacent row is a little bit tricky so I will handle the adjacent column in the same rowsl first. That's a matter of wrapping around the ends of row, which in my sinusoid wrap around the globe at that latitude.

The correct quad in the adjacent row, upper or lower. Is straightforward, getting the top or bottom width of each row from the correct corners of the first and last quads. I get the top or bottom left end, add some random distance to the right, divide by the width and multiply by the number of columns flooring it to find the column and index of the quad the program randomly walks to...