A luopan is built around a central magnetic needle surrounded by dozens of concentric printed rings, each ring encoding a different system, the Later Heaven Bagua, the twenty four mountain directions, the heavenly stems and earthly branches, and star correspondences among them, which makes it closer in complexity to a specialized surveying instrument than to a simple compass.
A specific, shrinking craft
Producing one requires three combined skills, precision woodworking for the base, fine calligraphy or printing for the rings, which must align exactly with the needle, and compass calibration itself, a combination historically concentrated in a small number of specialist workshops, Xiuning county in Anhui among the most documented centers of the trade, a craft now under pressure from mass produced simplified compasses and phone applications that replicate the calculations without the physical instrument.
Who uses it, and how it is kept
A luopan is not restricted from ownership, but correctly reading it, rather than simply owning one, is a trained feng shui practitioner's skill, comparable to owning a sextant without knowing celestial navigation. A working luopan is kept away from other magnetic objects that could throw off its needle, and a serious practitioner periodically checks its calibration, treating it as a professional tool to be maintained rather than a decorative object to be displayed.