Tidal atlas¶
A regional sequence of charts predicting tidal-current direction and speed by tidal hour, using arrows, rate annotations, spring/neap values, and slack-water markings relative to a named reference port or phase.
Core Idea¶
A tidal atlas or tidal stream atlas is a set of regional charts used to predict tidal-current direction and speed. A typical atlas has 12 or 13 panels centered on successive tidal hours. Arrows show flow direction; length and thickness indicate approximate strength, and numbers may give more precise rates. Slack areas can appear without arrows or with a label. British Admiralty atlases commonly report rates in tenths of a knot, with paired mean neap and spring values at a marked point.
Scope of Application¶
Use tidal atlas with edition, region, reference port and event, tidal-hour convention, date and time conversion, spring-neap factor, vector legend, rate units, and weather/local-current limitations stated. Use tidal atlas with edition, region, reference port and event, tidal-hour convention, date and time conversion, spring-neap factor, vector legend, rate units, and weather/local-current limitations stated.
- Navigation planning. Estimates current windows.
- Sailing. Anticipates favorable or adverse flow.
- Search and rescue. Bounds drift scenarios.
- Marine operations. Schedules current-sensitive work.
- Coastal education. Visualizes tidal streams.
Clarity¶
The atlas compresses continuous space and time into discrete arrows and hourly panels. Interpolation is therefore structural, not optional, whenever a route lies between arrows or phases. The closest near miss sets the boundary: A tide table is closest: it predicts heights and times at locations, while a tidal atlas spatially maps horizontal current direction and speed by phase.
Manages Complexity¶
Prediction describes astronomical tide under modeled conditions. Meteorological and river effects can alter both rate and timing, so atlas precision should not be confused with real-time observation. The central compact prediction–continuous variability tradeoff is this: Hourly arrows aid planning while currents vary continuously in space and time.
Abstract Reasoning¶
Use three linked moves: identify region, edition, reference port, and phase event; convert the intended time to tidal hour; locate the route within the correct panel. As a collapse test, the case exits when there is no tidal-phase sequence or the arrows describe a fixed or measured current without tidal prediction.
Knowledge Transfer¶
Phase-indexed vector cartography transfers to cyclic flows, but coastal tidal prediction and reference-port timing delimit tidal atlases. The nearest stopping boundary is explicit: A tide table is closest: it predicts heights and times at locations, while a tidal atlas spatially maps horizontal current direction and speed by phase. The inclusion test remains: An artifact is a tidal atlas when it presents a phase-indexed regional sequence of charts encoding predicted tidal-stream vectors and rates through a cycle. The structure no longer applies when the case exits when there is no tidal-phase sequence or the arrows describe a fixed or measured current without tidal prediction. No canonical parent prime is currently asserted; broader structural comparisons remain related-prime analogies until separately adjudicated in the DAG. It supplies height and timing rather than vector fields.
Relationships to Other Abstractions¶
Current abstraction Tidal atlas Domain-specific
Parents (1) — more general patterns this builds on
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Tidal atlas is a kind of Representation Prime
Tidal atlas is a strict kind of Representation: its frozen identity entails the parent's defining structure while adding domain-specific restrictions.
Hierarchy path (1) — routes to 1 parentless root
- Tidal atlas → Representation → Abstraction
Neighborhood in Abstraction Space¶
Tidal atlas sits in a moderately populated region (50th percentile for distinctiveness): it has near-neighbors but no dense thicket of look-alikes.
Family — Domain-Specific Measurement Parameters (36 abstractions)
Nearest neighbors
- Cotidal Line — 0.90
- Rossby whistle — 0.86
- Turner angle — 0.86
- Draft survey — 0.85
- Iribarren Number — 0.85
Computed from structural-signature embeddings · 2026-10-08