MMO Range Finder vs Maritime Master
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
MMO Range Finder
This app helps Marine Mammal Observers calculate distances between animals and acoustic sources during surveys. It uses trigonometric functions and allows users to input target and source bearings and distances for precise mitigation decisions.
- Calculate distance using trigonometric cosine function
- Fix compass bearing by pointing device
- Convert binocular reticules to distance
- Set up to 3 unique observation locations
- Save and export sighting data in .csv format
- Display vessel position, mitigation zone, and sightings on map
- Customise MMO parameters
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Marine Mammal Observers mitigate for the potential impact of sound exposure on marine fauna during geophysical surveys, naval active-sonar exercises, UXO clearance or civil engineering projects. This app will assist the MMO making mitigation decisions by calculating the distance from the animal to the source of acoustic interference using a trigonometric cosine function. The MMO simply enters the distance and bearing to the TARGET and SOURCE from their observation position and the app calculates the rest. This app is loaded with features to make allow to keep focused on the detection (See the user manual for a detailed description): Fix compass bearing to animal and source by pointing device and pressing button. Convert binocular reticules to distance by entering the number of reticules between horizon and animal and pressing the reticule button (per formulae in Lerczack and Hobbs, 1998). Set up to 3 unique observation locations to define height above sea level (required for accurate reticule conversion). Save data to the log for each sighting and export in .csv format for your own mapping and analyses needs. Shows vessel position, mitigation zone and projected fauna sightings on the map. Map also displays latitude, longitude, course and speed. Press the radar button and the map will orientate to the vessel point of view. Sightings labels will be updated live with the distance to source and the bearing from the vessel for ease of re-sighting. Fully customise the MMO parameters. Specify anything from your binocular MILs per reticule, mitigation zone size, choose a ramform hull as your maps ship symbol and much much more! Disclaimer: MMO Range Finder App should be used as a reference tool and is only as precise as the users ability to range find. Any decision making is the responsibility of the user. If in use, the compass and GPS location should be verified often.
Maritime Master
This app provides a comprehensive suite of 88 professional maritime calculators for navigation, celestial observation, tides, stability, weather, engineering, and more. It's designed for maritime professionals and enthusiasts, offering offline functionality and citing all formulas with their official sources.
- 88 professional maritime calculators
- Offline functionality
- Navigation calculations
- Celestial observation tools
- Stability and cargo calculations
- Unit converters
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CalcDeck is the complete calculation toolkit for life at sea. It brings 88 professional maritime calculators into one beautifully designed iOS app, covering navigation, celestial observation, tides, stability and cargo, weather, engineering, safety, commercial voyage work, yacht and small craft performance, regulatory compliance and unit conversion. Whether you are a Master Mariner, deck officer, marine engineer, maritime cadet, yacht skipper or weekend sailor, CalcDeck replaces a shelf of reference books, a scratch pad and a pocket full of single-purpose apps. Every formula is cited with its textbook or IMO source, so you can verify the working and trust the result. CalcDeck is built by Maritime Master, the team behind COLREG Master, Nav Lights and IALA Buoyage, and is engineered to the same professional standard trusted by cadets and officers worldwide. What is inside Navigation (12 calculators): great-circle and rhumb-line distance, course to steer, ETA, set and drift, three-point fix, running fix, dead reckoning, cross-track error, waypoint bearing, speed-time-distance, departure and DMP, Mercator sailing. Celestial (8 calculators): sight reduction, meridian passage, altitude corrections, sunrise, sunset and twilight times, Polaris latitude, compass error by amplitude, azimuth of the sun, and chronometer error. Tidal (6 calculators): tidal height by the rule of twelfths, secondary port corrections, tidal streams, height at a given time, time at a given height, and clearance under bridges. Stability and Cargo (9 calculators): GM and list, trim and draft survey, free surface correction, deadweight and displacement, cargo load, block coefficient, TPC and MCTC, and final draft after loading. Weather (6 calculators): true wind, apparent wind, relative humidity, dew point, Beaufort scale conversion, and barometric trend. Engineering (10 calculators): fuel consumption and ROB, daily fuel burn, propeller slip, shaft power, specific fuel consumption, bunker density correction, trim tank transfer, admiralty coefficient, engine load, and voyage fuel planning. Safety (5 calculators): distance off by vertical sextant angle, horizon distance, dipping range, turning circle, and stopping distance. Yacht and Small Craft (5 calculators): hull speed, sail area to displacement, displacement to length, capsize screening, and ballast ratio. Commercial and Voyage (6 calculators): voyage cost, laytime, demurrage, freight rate per tonne, charter economics, and port disbursements. Regulations and Compliance (6 calculators): MARPOL discharge limits, SOLAS LSA requirements, STCW rest-hour compliance, load line zones, ballast water exchange, and garbage record categorisation. Unit Converters (12 calculators, all free): distance, speed, temperature, pressure, volume, mass, area, power, energy, angle, time and fuel. Every unit a mariner needs. Why CalcDeck CalcDeck works fully offline, so there is no signal, no signup and no interruption when you need an answer at sea. It is a native SwiftUI app designed for iPhone and iPad on iOS 17 and later, with a clean navy and gold Maritime Master design, dark mode support, favourites, and a Calc Pad that lets you pin your most-used tools for instant access on watch. There are no advertisements, no tracking and no subscriptions. Free and Pro You can try CalcDeck at no cost. All 12 unit converters and a selection of essential calculators in every professional category are included free. Unlock the full 85-calculator suite with a single one-time in-app purchase that is yours forever across all your devices. Who it is for CalcDeck is used by deck officers and Masters on coastal and ocean passages, by marine engineers calculating fuel, power and performance, by maritime cadets preparing for OOW, Chief Mate and Master examinations, by yacht skippers and RYA students, by cruising sailors, by pilots, harbourmasters and port operations staff, and by naval architects, surveyors and marine consultants.
Screenshots
Verdict
The clearest difference is review sentiment: MMO Range Finder at 100% against Maritime Master's 0%. MMO Range Finder also leads on rating (5.0 vs 3.0) and in-app purchases (none vs 1). Maritime Master's advantage is price (Free vs $0.99) and update cadence (daily vs every 2 months). On ratings volume, ads and device support there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Maritime Master is free to download; MMO Range Finder costs $0.99 up front. Maritime Master sells 1 one-off in-app purchase. MMO Range Finder asks for nothing beyond the download.
MMO Range Finder holds the better App Store score, 5.0 against 3.0. Both are backed by a comparable volume of ratings — 1 and 1 respectively. Written reviews point the same way: 100% of MMO Range Finder's written reviews are positive against 0% of Maritime Master's.
MMO Range Finder ships an update every 2 months, Maritime Master daily. The most recent releases landed on November 2, 2026 and November 5, 2026 respectively.
| Parameter | MMO Range Finder | Maritime Master |
|---|---|---|
| Price | $0.99 | Free — better |
| Rating | 5.0 (1 ratings) — better | 3.0 (1 ratings) |
| Positive reviews | 100.0% of reviews — better | 0.0% of reviews |
| Number of ratings | 1 | 1 |
| Update frequency | Every 2 months | Daily — better |
| Ads | No | No |
| In-app purchases | No — better | Yes |
| Monetization | Paid | Free — better |
| Devices | iPhone, iPad, iPod — better | iPhone, iPad |
| Requires iOS | 10.3 — better | 17.6 |
| Further details — not scored | ||
| Size | 43 MB | 7 MB |
| Age rating | 4+ | 9+ |
| Developer | James Keating | MARITIME MASTER LIMITED |
Customer experience
MMO Range Finder
Maritime Master
In-app purchases
MMO Range Finder
No in-app purchases
Maritime Master
- CalcDeck Pro$14.99
Questions
Is MMO Range Finder free?
Is Maritime Master free?
Which has better reviews, MMO Range Finder or Maritime Master?
Do MMO Range Finder or Maritime Master have ads?
Which is updated more often, MMO Range Finder or Maritime Master?
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