A short written artifact kept beside a scene, plus a mechanical pass run over the finished draft. It borrows Tolkien’s method — consistency held in an external document rather than in the writer’s head — and film continuity’s insight that this cannot be done from memory while also writing.

The ledger is not published and is not prose. It is scaffolding, and it should take about five minutes.

Step 0 — The invariants#

Learn these once. They are true in every gyrealm and they never change.

• Down is outward from the axis. Up is toward it. Down is not an absolute; two people on opposite sides of the cylinder have opposite downs.
• West is the direction of spin. East is against it. This is the opposite of the naive guess, and it is deliberate — see the next two bullets.
• North is the right-hand-rule thumb on the rotation vector, per the geographic coordinate system. South is the other end.
• Facing north, east is on your right. Same as Earth — and the reason the previous two bullets read as they do. Up points inward here, which would mirror the local frame; defining east against the spin un-mirrors it. Reach for this directly when a scene needs a character’s left or right; re-deriving it from the hand rule mid-draft is how it comes out backwards.
• There is no horizon. The ground curves up in the east and west until it closes overhead. It recedes and converges to the north and south. Far away and toward the sky are different directions.

And the deflections, which are the part most often gotten wrong. Every one of these follows from the same fact: the floor moves faster at larger radius.

The first row is why Scimitar Falls curves the way it does. The last row is worth remembering because it is the only free direction in the habitat: a north–south journey is the one that behaves like Earth.

Step 1 — Fill the ledger#

Before writing, write down:

1. Position. Axial distance north or south of the origin; where around the circumference; what level.
2. Facing. Which of the six directions the point of view is looking. If the POV turns during the scene, note where.
3. Overhead. What is actually up there — land, sky, or a structure — and how far.
4. Up-axis. What is visible to the north and to the south, and at what distance.
5. Light. Where the sky is, what point of the cycle, and whether light is moving; if so, which way.
6. Landmarks. Every named thing the scene can see, with its bearing and distance from the POV.
7. Anything in motion, with its deflection from the table above.

If a field cannot be filled because canon does not say, that is a finding, not a blocker. Record the assumption in the ledger, write the scene, and raise the question. Three such questions came out of the audit this way.

Step 2 — Derive before you draft#

The ledger’s fields are inputs. These follow from them, and getting them from the ledger rather than from intuition is the point of the exercise:

• What does the POV see when they look up?
• Which way does dawn arrive from?
• Which direction is distance — and is the distant thing up-axis or around the curve? These are the two that Earth conflates.
• Which way does everything that moves drift?
• What is the circumferential span, as distinct from the axial one? A 20 km cylinder has a circumference of 62.8 km. The 80 km axial length is not a distance that exists around the curve, and reaching for it because it is the number you happen to know is how it ended up in five of the six renderings.

Step 3 — Draft, using the vocabulary that exists#

Prefer spinward and antispinward where the rotation is the point, and east and west where a compass reading is the point. Both are in-world and inhabitants use them.

Give the overhead a clause in every outdoor scene. It is the densest orientation object available and it costs almost nothing — this is Niven’s method, described in existing solutions.

Step 4 — Run the check pass#

Over the finished draft:

grep -oniE '\b(north|south|east|west|spinward|antispinward|up|down|above|below|overhead|underfoot|left|right|horizon|sunrise|sunset|rise|rose|climb|fell|falling|drift|lean|far|distant|beyond|across|toward|away)\b' draft.md

The pattern deliberately over-collects; most hits are innocent and clearing them is fast. Resolve each against the ledger into one of three outcomes:

• Resolves. Consistent with the ledger. Move on.
• Contradicts. Fix the prose, or fix the ledger if the ledger was wrong.
• Unresolvable by a reader. The word is not wrong, but nothing in the text lets a reader determine what it means. This is the category that matters most, and it is the one attentive re-reading never catches, because the writer always knows what they meant. “The deflected currents pull at them from the west” sits here.

Then check the trap list specifically — words that carry a false frame rather than a wrong direction:

horizon · sunrise · sunset · the sun climbed · across the valley · the far shore · to the horizon · on the level

Each of these asserts a planet. Some can stay as deliberate Earth-nostalgia in a character’s idiom; none should pass unnoticed.

Step 5 — The pointing test#

At each paragraph break, ask whether a reader who has read only this text, attentively, could point at:

1. the sky,
2. the nearest named landmark,
3. the far end of the habitat.

If any of the three has gone unanswerable, orientation has drifted, and the fix is usually one clause rather than a rewrite.

Worked example#

The ledger for Dawn at Scimitar Falls, filled from canon:

Two of seven fields could not be filled. That result is the technique working: those two gaps are the direct cause of four of the five defects in the audit, and they were invisible for as long as nobody tried to write them down. Filling out a form found in five minutes what six careful renderings did not surface in six attempts.

Limits#

The ledger checks consistency, not quality. A scene can pass every step and still be inert. It also cannot check what canon has not decided — it can only make the undecided thing visible, which is a smaller claim than it sounds and still the most useful thing it does.

It is scene-scoped by design. Consistency between scenes — a landmark that moves between chapters, a habitat whose scale drifts across a book — needs a corpus-level pass that this technique does not provide. That gap is noted in speculative notes.