The Sailing Model

First notes — the seed of the sailing model, graded the way the charts are graded.

How a boat moves in Tessamar's charted water, beginning with the one road the atlas has actually surveyed: the Deepgate. This is the seed of the sailing model — the layer the game will stand on — graded the way the charts are graded.

The grading

• Proven — the plates themselves show it: a channel's shape, a tide the plates arrow, a width the survey measured.
• Estimated — read off the plates' framing by geometry, not surveyed in its own right. Said as an estimate, never as fact.
• Unwritten — what no plate has measured yet. Left blank on purpose, the way the charts leave blank ground blank.

The tide, which is the road's law (proven)

The Deepgate runs between Varra's Shiproad Shore and the unnamed dome across the water. The strait is widest at its south mouth and narrows northward, toward the Stepping Stones, and the true channel runs mid-strait, bending slightly toward the eastern isle at the south end. Pale shallows fringe both coasts, so deep-draft boats keep to the channel and small boats can work in close.

The flood tide sets northward through the Gate, hard along the channel — and hardest at the northern narrows, near the Stones, where the strait is tightest. The formal plate arrows the flood north past the Stones in the eastern sea, not only through the channel south of them: the Gate's fast water reaches beyond its door.

On the ebb the water turns and slides south — and at Gathaven's mouth it does the thing that makes the haven a haven. The southward water curls into the bay: a slow back-eddy, a settling bowl. Silt settles there with it, so the bottom is soft and the holding good — a harbor that silts slowly and must be sounded, not trusted.

That is the whole law of the road, and every sailor in the Gate learns it as one sentence: you ride the flood north, and you come home on the ebb, and the bay catches you.

The first voyage

The first voyage the model charts is a homecoming before it is anything else: in from the Unwritten, through the Gate's north door, and down to Gathaven — timed so the last and longest leg runs on the ebb, because the ebb is the tide that delivers a boat to the haven.

Leg one — the Unwritten to the Stepping Stones. You come out of the open sea to the north, where no chart runs, and the first land you raise is the Stones: two low domes on a southwest–northeast line in a wide shallow apron, the larger to the northeast. Proven: the northeast stone stands at rows 237–292, cols 858–923, its summit (265, 897) at 0.5502; the southwest stone at rows 296–319, cols 829–853, its summit (306, 841) at 0.5457. From the northern edge of their charted frame the northeast stone's shore is some 40 cells of frame water. Unwritten: how far the sea road runs before that frame edge — the Unwritten has no distance by definition, and a boat sails it by dead reckoning until the Stones show. Between the two summits is about 69 cells, measured across the neck.

The neck is not a harbour. The saddle between the Stones sits at ~0.5207, seven ten-thousandths above the sea: awash in all but name. You do not beach across it and you do not shelter behind it. It is a wading crossing, not a walk, and in any honest tide the Stones are two islets, not one footprint.

Leg two — the Needle's Eye. Off the southwest stone's point at (310, 827), Varra's cape reaches its hooked point at (323, 804), and the gut between them is the Needle's Eye: about 26 cells at the closest approach. Small boats only — the chart has said so since the strait was first drawn, and the closer look showed why: a boat that threads the Eye is choosing the Gate's quickest water at its tightest point. You take it on the turn of the tide, as the ebb begins, so the new southward set is with you and not yet at its hardest.

Leg three — the Eye to Gathaven, on the ebb. South of the cape, Varra's east coast runs down the Shiproad Shore, and the ebb slides south along it with you. Mid-plate, below the cape, one real bay bites into the coast — the only sheltered water on this side: Gathaven. You do not fight for its mouth. The southward water passing the mouth curls in, and the back-eddy carries a boat off the road and sets it down in the settling bowl, where the bottom is soft and the holding good. Estimated: the run from the cape's hook to the bay's mouth is a short coastal leg, on the order of tens of cells, read from the plate's framing — the bay's mouth carries no fixed surveyed point of its own, so no exact figure is claimed. Sound your way in the last of it: the haven silts, and a silting harbour is sounded, not trusted.

The return, for completeness: out of Gathaven on the flood, which sets north hard along the channel, hardest at the narrows by the Stones; then out past the Stones to the open sea, or through the Eye again if your boat is small and the tide is kind. The road runs both ways. It only ever runs on the tide's schedule, not the sailor's.

What is not yet known (unwritten)

• Speeds. The plates arrow direction and relative strength — hardest at the narrows — and nothing more. No current in the Gate has a measured speed, and no passage in this note has an honest time on it. Hours and knots stay blank until the model earns them.
• Depths in the Eye. The gut's width is surveyed (~26 cells); its soundings are not. A small boat threads it on a chart that knows how wide the door is, not how deep.
• The length of the Unwritten leg. By definition. The chart begins where the chart begins.
• Weather. This note is written for the tides as the plates arrow them. What wind does to the ebb's curl, or to the shallows' fringes, no plate has yet been asked.