I'm working on a large sheet, trying to make a contour map for my house block. Something has happened to basic excel logic. E.g. autofill dragging a simple number list, descending by 0.1, corrupts after 10-20 lines and starts subtracting 0.00000000000001 (14 decimal points) randomly, so failing match results. I also think I'm creating a formula poorly, as I'm a rookie user. Interpolate is doing X or Y, not both at once. Questions: Can you help me solve dragging calculation bug, improve my formula, and suggest any better interpolate formula?
Solved by K. S. in 27 mins