Learn · Instrument · 17 min read · Updated September 2026

The luopan and the twenty-four mountains

The feng shui compass is a magnetic needle inside a stack of rings, and it is older than the mariner’s compass by a thousand years of texts. Where it came from, what the rings are and which one to read, why there are twenty-four sectors rather than eight, the three plates of the San He instrument and the two norths, and how a reading is taken and written down.

Oriented N 000°

Water

Fig. 01 Water seen from above, with no landmark. The compass was the tradition’s answer to ground that gave no bearing of its own.

A luopan is a compass, and it is not only a compass. At its centre sits a magnetic needle in a small well, the heaven pool. Around the well turn concentric rings, from a handful on a simple instrument to forty on a full one, each a different scale for reading the same bearing. Everything the Compass schools do begins with this object, and the dial on every page of this site is a reduction of it: the needle, one ring of twenty-four, and nothing else.

The needle before the navigator

Fig. 01 The instrument’s descent, with the dates the texts themselves give. It begins with the shi, the cosmograph of the Han: a round heaven plate turning on a pin above a square earth plate, the heaven plate carrying the Dipper and the lunar mansions, the earth plate carrying twenty-four names around its rim. Those twenty-four are the mountains of the modern luopan, and they are older than the compass by centuries, because they were a way of naming the sky before they were a way of siting a house. Wang Chong describes a south-pointing spoon about 80 CE, and Needham’s reconstruction sets it on the bronze plate of such a board. In 1088 Shen Kuo describes a needle rubbed on a lodestone, records that it always inclines slightly to the east, which is the first notice of magnetic declination anywhere in the world, and tries four ways of mounting it, drawn along the bottom of this sheet: floating on water, balanced on a fingernail, resting on the rim of a bowl, and hung from a single fibre of new silk, which he found best. Only in 1119 does Zhu Yu put the needle in a sailor’s hands, thirty years after the diviner had it. By the Ming the instrument has the form it keeps: a square base of hardwood, a dial that turns within it, a red thread stretched across to read against, and the ring of twenty-four names that came off the Han board and has never left. Wang Chong, Lunheng, c. 80 CE; Shen Kuo, Mengxi Bitan, 1088; Zhu Yu, Pingzhou Ketan, 1119; Needham 1962 for the reconstruction and the order, Li Shu-hua 1954 for the same reading of the same texts. The instruments are drawn as diagrams of their principle, not as portraits of surviving examples.

Evidence · Needham’s finding

The magnetic compass appears in Chinese texts as a diviner’s instrument before it appears as a navigator’s. Wang Chong’s Lunheng, written about 80 CE, describes a south-pointing spoon that, thrown on the ground, comes to rest pointing south. Shen Kuo’s Mengxi Bitan of 1088 describes a needle rubbed on a lodestone that points south but “always inclines slightly to the east,” the first record of magnetic declination anywhere, and tries four ways of mounting it: floating on water, balanced on a fingernail, resting on the rim of a bowl, and hung from a single fibre of new silk, which he found best. Zhu Yu’s Pingzhou Ketan of 1119 is the first text to put the needle in a sailor’s hands, thirty years later. Needham’s history of physics traces the geomantic compass back to the diviner’s board of the Han and concludes that siting, not seafaring, drove its early development; Li Shu-hua’s reading of the same texts reaches the same order.

The ancestor of the luopan is the shi, the cosmograph of the Han dynasty: a round heaven plate that turned on a pin above a square earth plate. The heaven plate carried the Dipper and the twenty-eight lunar mansions; the earth plate carried, around its edge, the twelve branches, eight of the ten stems and the four corner trigrams, twenty-four directions in all. The twenty-four mountains are therefore older than the compass by several centuries, and were a way of naming the sky before they were a way of siting a house. Needham’s reconstruction puts the lodestone spoon of the Lunheng on the bronze earth plate of such a board, its handle swinging to the south, and the round plate, the square base and the ring of twenty-four names have never left the instrument since.

Between the spoon and the luopan lie three changes. The spoon became a needle, magnetised by stroking it on the stone, which Shen Kuo describes as a thing magicians did. The floating needle became a needle on a pivot in a closed well, which the Southern Song manuals describe and which the tradition kept. And the plate acquired rings: by the Ming the instrument had the form it keeps today, a square base of hardwood, a round dial that turns within it, a red thread stretched across in each direction to read against, and a name, luopan, the plate of the net, from the older luojing, the net classic, the net being, by the usual gloss, the mesh of lines the rings throw over the ground.

The anatomy of the instrument

Fig. 02 The anatomy of a luopan, from the centre out. The heaven pool holds the needle over a red line that gives it its rest, the south end marked. Around it the rings: the eight trigrams in the Earlier Heaven order, which every instrument carries and no reading uses; the earth plate, the twenty-four mountains on which the facing and the sitting of a building are read; the seventy-two dragons, each mountain divided in three and given a stem and a branch; the human plate, the same twenty-four mountains turned seven and a half degrees anticlockwise, on which the San He school reads the surrounding hills; the hundred and twenty gold divisions, five to a mountain, the fine scale on which a coffin or a ridge is set; the heaven plate, the mountains turned seven and a half degrees clockwise, for the water; and the twenty-eight lunar mansions, the sky’s own ring, with the three hundred and sixty degrees outside them. The square base carries two red threads at right angles, and a reading is taken where the thread crosses the rings. A key, not a working dial: the rings are drawn as bands and their divisions are left off, and a real instrument carries between a dozen and forty of them in an order that varies by maker and school. The Mountains drawing below gives the one ring a reader needs in full. The names and the order here follow Skinner’s compendium and the Wanan instruments of Anhui, made in the same workshops since the eighteenth century.

Start at the centre. The heaven pool, tianchi, is a round well under glass in which the needle floats or pivots; on its floor is drawn a red line with two dots at one end, the line the needle is brought to rest along when a reading is taken. The needle’s south end is the one the tradition marks, because the Chinese compass points south by convention as a European one points north; both ends point somewhere, and the choice is a habit.

Around the pool the rings. The innermost on most instruments is the eight trigrams in the Earlier Heaven order of Fu Xi, which every luopan carries and which no reading uses, a signature rather than a scale. Then comes the ring everything depends on: the earth plate, dipan, with its twenty-four mountains of fifteen degrees each, the ring on which the facing and the sitting of a building are read and the only one a reader with a compass has. Outward from it, on a San He instrument, come the seventy-two dragons, each mountain divided into three and each third given a stem and a branch from the sexagenary cycle; the human plate, the twenty-four mountains again, turned half a mountain; the hundred and twenty gold divisions, five to a mountain, the fine scale on which a grave or a ridge line is set; the heaven plate, the mountains turned half a mountain the other way; and the twenty-eight lunar mansions with their widths in degrees, the sky’s own ring, with the three hundred and sixty degrees of the circle marked outside everything. A San Yuan instrument drops the offset plates and adds the sixty-four hexagrams and the rings of the nine stars its method needs. A combined instrument carries both sets and is the one most often sold.

The base is square, of wood, and carries two red threads, or on modern instruments two lines under a glass plate, that cross at the centre at right angles: the ten lines of heaven’s heart, so called from the shape of the character for ten, 十. The dial turns within the base; the threads do not. A reading is the point at which a thread crosses a ring. The dials come in sizes: a pocket instrument of two and a half Chinese inches across, about eight centimetres, carries five or six rings; a master’s instrument of ten or twelve, a third of a metre across, carries them all.

The twenty-four mountains

Eight directions are too coarse to site a building. The luopan’s basic ring therefore divides the circle into twenty-four sectors of fifteen degrees, three to each direction, and calls them mountains, shan. The names are borrowed from three older sets: the twelve earthly branches, the cycle behind the animal years, give twelve; eight of the ten heavenly stems give eight more, since the two earth stems, Wu and Ji, belong to the centre and have no direction; and the four corner trigrams, Gen, Xun, Kun and Qian, fill the four remaining sectors. Twelve, eight and four make twenty-four. The twenty-four mountains are listed in ring order on their own page, with the bearing, the character, the source and the element of each.

Fig. 03 The twenty-four mountains. Each of the eight directions is divided into three sectors of fifteen degrees, named from the twelve branches (the animals), eight of the ten stems, and the four corner trigrams. The tint is the sector’s element; the centre sector of each direction is the branch that names it: Zi for north, Mao for east, Wu for south, You for west. Drawn north up. A classical luopan is read with south at the top, and its dial is turned until the needle sits in the red thread; the reading is then taken from the ring under the thread.

Fifteen degrees is roughly the width of a hand held at arm’s length. That is the resolution at which classical siting works, and it is why practitioners argue about instruments and readings. A phone compass is good to a degree or two; a building that faces 21° and one that faces 24° sit in different mountains, N3 Gui and NE1 Chou, and a Compass practitioner will treat them differently. A reading within a degree or two of the line between two mountains is what the schools call a void line, and the facing guide says what to do with it, which is mostly not to force it.

The three plates

School · Correct, middle and seam

A San He luopan carries the twenty-four mountains three times over. The earth plate is the plain ring, the correct needle, zheng zhen, and the facing and the sitting are read on it. The human plate, the middle needle, zhong zhen, is the same ring turned seven and a half degrees anticlockwise, and the school reads the surrounding hills and buildings on it; the tradition credits it to Lai Wenjun of the Song. The heaven plate, the seam needle, feng zhen, is the ring turned seven and a half degrees clockwise, for the water, the roads and the approach; the tradition credits it to Yang Yunsong of the Tang. Needham argued that the three needles are three historical values of the magnetic declination, fixed on the instrument when each was set and kept after the pole had moved on, which would make the luopan a record of the wandering of the magnetic north pole over eight centuries. Whether or not he was right, a reader with a compass has only the earth plate, and the earth plate is the one that matters.

De Groot, watching Fujian geomancers in the 1880s, described the instrument with the mixture of scepticism and fascination that most outsiders feel: an object of great precision applied, he thought, to a question that precision could not answer. Eitel, a decade earlier, had called the system “the rudiments of natural science,” and meant it half as praise. Smith’s survey of the divinatory arts of the late empire places the luopan among the almanacs, the horoscopes and the diviner’s stalks as the most respectable of them, because it measured something. All three were right about the object: it is a serious instrument, and the only one in the tradition that gives the same answer to two people.

Taking a reading

Fig. 04 Taking a reading. A: stand inside the doorway facing out, hold the plate level with one edge square to the door, and turn the dial until the needle rests in the heaven pool; the red thread that runs from you through the door crosses the outer ring at the facing. B: take it three times, at the threshold, a pace inside and a pace outside, and keep the one that repeats. C: steel in a door frame, a car at the kerb or a radiator pulls the needle; a reading that changes as you move is one to take again a metre further on. The plate is drawn from above, as the person holding it sees it. The dial turns under the fixed threads; the outer ring here carries the twenty-four mountains, and a full luopan carries many more rings beneath.

The procedure is simple and the tradition surrounds it with care. The drawing shows it as the manuals teach it, at the door; the facing guide does the same reading outside the house, which is where a modern building’s steel makes it more reliable.

Decide the facing side first. It is the open, active elevation, the side of the road and the light; in most houses it is the side of the front door, and in a flat it is usually the building’s, not the flat’s.
Stand on the facing line with your back to the house, a metre or two out, holding the luopan level at the waist with one edge of the square base parallel to the facing wall. The base, not the dial, is what you align with the house.
Turn the dial until the needle rests exactly along the red line in the heaven pool, its marked end between the two dots. Wait for it to settle; a needle that will not settle is a needle being pulled.
Read the thread. The red thread that runs from you away from the house crosses the earth plate at the facing mountain; the same thread on the near side crosses it at the sitting. Read the mountain and, on the outer ring, the degrees.
Take it three times, at three points along the facing line, and keep the reading that repeats. If the three differ by more than a few degrees, something is pulling the needle and the reading is taken again further out.
Write it down as the tradition does, sitting first and facing second: sits Zi, faces Wu, 358° and 178°, with a note if the reading is within two degrees of a line.

A reading of 178° falls in S2 Wu, and its opposite, 358°, in N2 Zi: the house sits Zi and faces Wu, zuo Zi xiang Wu, the pair the manuals use as their standard example because it is the ideal orientation of a Chinese house, back to the north and face to the noon sun. From the sitting the Eight Mansions method gives the house its trigram, Kan, and its group, East; from the facing and the year of building the Flying Star method draws its chart. Nothing in the Form reading needs the number at all.

Magnetic north, and the rest

The ring on this site’s dial, and on the explorer, carries the twenty-four mountains as its tick marks: three to each direction, the long ticks at the cardinals. When the explorer says a wall faces “E 090°” it is reading the Mao mountain, the middle third of the east, and the direction pages tell you what the tradition makes of that. A reader who wants the other thirty-nine rings will find them in Skinner, and will find, as he says, that most of them answer questions a house does not ask.