Reference · The exact facts

Reference

The precise facts you'll come back to: which units MuirWave uses and how to change them, what the Depth-Excess colours mean, what each edition unlocks, and the data sources behind every number. Everything here is a lookup, not a tutorial.

§01

Units & conventions

MuirWave opens with traditional nautical-chart conventions. Every value is stored internally in SI units and shown through your chosen display unit — so switching units never changes the underlying result. Set them in Settings → Units, where every option for every quantity is laid out at once, or tap most readouts in the app to cycle that field without leaving what you're doing. Both write the same preference.

Your units belong to you, not to a scenario: they survive a relaunch, they survive RESET, and opening a colleague's project won't re-skin the app in whatever units they happened to work in. The project file still records the units it was authored in, so that context isn't lost — it just doesn't overwrite yours.

Quantity	Default	Also available	Notes
Depth	feet	metres · fathoms	Depth-Excess thresholds are always judged in fathoms (see §02), whatever your depth unit. Vessel draught follows this too.
Range / distance	nautical miles	km · statute miles · yards · metres	Convergence-zone spacing, detection range, impact and mitigation ranges, platform ranges, and visibility all follow this.
Latitude / longitude	DMS	DDM · DD	e.g. 56° 42′ 19″ N. Pick the format your charts use.
Speed	knots	m/s · km/h · mph	One setting covers wind and gusts, current set & drift, and vessel speed over ground.
Temperature	Celsius	Fahrenheit	Sea and air temperature, the SVP profile axis, and the water-column readouts.
Sound speed	m/s	ft/s	The SVP cursor read-out and the water-column legend.
Wave & swell height	follows depth	—	No separate setting: sea state reads in whatever unit you read soundings in, so feet gives you 7.9 ft seas.

Why feet, nm and DMS by default? Because those are the conventions on a nautical chart, not arbitrary defaults. If you work in SI, one pass through Settings → Units switches everything, and it stays switched.

Short ranges drop to metres. Below one whole unit, a range is shown in metres regardless of your setting — a 555 m mitigation zone reads 555 m, not 0.3 nm. Near-field pile-driving zones are almost all sub-nautical-mile, and a fraction of a mile isn't a number you can work with.

Reports differ on purpose. The Brief Sheet and Propagation Report are written in your units. The Impact Assessment PDF and its Markdown twin are metric throughout — it's a cited document, and every threshold it references (NMFS, Southall, BOEM) is published in metric, so a reviewer checking a number shouldn't have to undo a conversion first — with one exception: the Level B behavioural-disturbance line follows your display-unit preference like the rest of the app. The Data (CSV) export is metric everywhere, Level B included, since a spreadsheet consumer wants a raw number rather than 1.9 nm.

Frequency isn't a unit choice — it's set on a continuous log-scale slider covering 10 Hz – 50 kHz, snapping at each decade. Any frequency in range can be dialled in, not just fixed stops.

§02

Depth-Excess colour bands

Depth Excess (DE) tells you whether the water is deep enough to support reliable convergence-zone propagation. The Profile panel colours the readout so you can judge it at a glance. Thresholds are always in fathoms, regardless of your chosen distance unit (1 fathom = 1.8288 m).

DE ≥ 300 fa · Green — reliable convergence-zone propagation (the conventional threshold).

200 – 300 fa · Yellow — marginal; CZ propagation may be unreliable.

0 – 200 fa · Grey — positive but too shallow for a dependable convergence zone.

DE < 0 · Blank — a depth deficit; no numeric readout is shown (a well-defined state that needs no number).

Detection-threshold presets

DT is the signal excess you need before "detected" is an honest word. The DETECT row's presets are keyed to how you're actually processing; each ⓘ in the app states the assumptions (50% probability of detection, the assumed false-alarm rate and integration time).

Preset	DT	Realistic window	Reference bandwidth
NARROWBAND · AUTOMATED	−5 dB	−8 … −2	1 Hz
NARROWBAND · SPECTROGRAM	−13 dB	−18 … −8	1 Hz
BROADBAND · ENERGY	0 dB	−4 … +6	your BANDWIDTH row
CROSS-CORRELATION	−18 dB	−24 … −12	1 Hz
CUSTOM	yours	−30 … +30	—

The bandwidth warning. A 1 Hz-referenced preset paired with a wide BANDWIDTH row silently mis-states SE by roughly 10·log₁₀(bandwidth) — up to ~20 dB. An amber note appears under the DETECT row whenever that mismatch exists — however it was created (picker, chip-cycling, or a later BANDWIDTH change) — with a one-tap SET BANDWIDTH TO 1 HZ fix. Manual DT entry flips the chip to CUSTOM.

§03

Editions — Free, Live & Pro

The full prediction engine is free. Two optional upgrades add live data and professional export. They're independent — buy either, both, or neither. Current pricing is always shown in the app before you purchase.

Capability	Free	MuirWave Live	MuirWave Pro
Prediction engine (rays, TL, sound field, impact ranges)	✓	✓	✓
Global bathymetry & climatology, fully offline	✓	✓	✓
iCloud sync of your scenarios	✓	✓	✓
Regional Climatology & Bathymetry packs (Compact / HQ)	✓	✓	✓
Watermarked Brief Sheet (draft, one page)	✓	✓	✓
Live ocean & weather data (SSP · WIND · CURRENTS chips)	—	✓	—
Regional Forecast packs (live ocean-model data)	—	✓	—
Clean Brief Sheet & Propagation Report (un-watermarked PDFs)	—	—	✓
Impact Assessment report & its data/figure exports (Markdown · CSV · GeoJSON · PNG)	—	—	✓
Mitigation screening panel (abatement systems, insertion loss, operational measures)	—	—	✓

MuirWave Live is a subscription (monthly or annual, with a free trial). It replaces climatology with real-time conditions and unlocks sharper regional packs. If it lapses, live lookups simply fall back to the built-in climatology — nothing breaks.

MuirWave Pro is a one-time purchase you own permanently. It unlocks the professional export tools — the Propagation Report, the regulator-ready Impact Assessment and everything exported from it — and the Mitigation screening panel (noise-abatement systems with frequency-dependent insertion loss and the mitigated-vs-unmitigated trade-off).

§04

Data sources

Every layer is public-domain or permissively licensed, and every prediction is traceable to a named source. The app's Provenance view lists exactly what fed each result; this is the summary.

Layer	Source	Role
Bathymetry	GEBCO 2025 sub-ice	Seabed depth everywhere.
Elevation	ETOPO 2022	Coast & terrain context.
Sound-speed profile	WOA23 climatology	The water-column baseline (offline default).
Sediments	Dutkiewicz 2015	Seabed type for bottom interaction.
Bottom loss	Hamilton 1980	How much sound the seabed absorbs.
Absorption	François-Garrison 1982	Sound absorbed by seawater with range.
Sound speed	Mackenzie 1981	Speed of sound from T, S and depth.
Ambient noise	Wenz 1962	Background sea noise for the sonar equation.
Live ocean LIVE	HYCOM	Real-time sound-speed & currents (MuirWave Live).
Live weather LIVE	NOAA GFS	Real-time wind, wave, rain & SST (MuirWave Live).

Impact thresholds follow the recognised marine-mammal criteria (NMFS 2024 or Southall et al. 2019, selectable) and fish/turtle criteria (Popper et al.), so your impact ranges line up with what regulators expect. The exact thresholds used appear in the methodology export.