I am currently building my first self designed delta printer (because the Chinese kits lack mechanical stability).
After setting up the firmware and some basic sizes (rods, z-height, ...), I tested the auto calibration method of Marlin. I was surprised, that this method came with slightly different horizontal distance values then I entered initially (~185 mm vs 190 mm).
Can someone explain what this method is actually doing, how it works in detail and how it calculates the horizontal distance, by just knowing the rod length? I have not found much more than it seems to be a "least square" method and tipping some points.