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. Tap any value to cycle its unit; your choice for that field is remembered.

Quantity	Default	Also available	Notes
Depth	feet	metres · fathoms	Depth-Excess thresholds are always judged in fathoms (see §02), whatever your depth unit.
Range / distance	nautical miles	km · yards · metres	Convergence-zone spacing, detection range and impact ranges all follow this.
Latitude / longitude	DMS	DDM · DD · MGRS / UTM	e.g. 56° 42′ 19″ N. Pick the format your charts use.

Why feet, nm and DMS by default? Because those are the conventions on a nautical chart, not arbitrary defaults. If you work in SI, two taps switches any field and it stays switched.

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)	✓	✓	✓
Markdown methodology export & watermarked Brief Sheet	✓	✓	✓
Live ocean & weather data (SSP · WIND · CURRENTS chips)	—	✓	—
Regional Forecast packs (live ocean-model data)	—	✓	—
Regulator-facing exports (formal report & methodology PDF)	—	—	✓
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 report and the regulator-ready methodology PDF that documents your inputs, data sources and results — 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.