Tactical Sailing Compasses Compared: Velocitek, Sailmon and Tacktick

Three devices, three sensor architectures. Velocitek's ProStart is a GNSS-plus-IMU start computer; Sailmon's MAX is a multi-band GNSS crossover display that also ingests the boat's instruments; Tacktick's Race Master is a fluxgate-magnetic tactical compass. The engineering that separates them is real — receiver channel count and update rate, inertial fusion, distance-to-line geometry, transflective display physics and power system — and it maps directly onto which job each does best on a Melges 40. For the wider system, see our race-boat electronics guide and the racing start explained.

At a glance

The three architectures

• Velocitek — a GNSS start computer plus a separate solid-state magnetic compass line. The ProStart (Gen2) pairs a 72-channel, 25 Hz multi-constellation receiver with a patented 100 Hz six-axis IMU and a 3-axis geomagnetic sensor; it is a distance-to-line and logging instrument, not a wind display. The Shift is a nine-axis AHRS tactical compass; the newer Prism is a stripped, purely magnetic compass (44 Hz sensor, ±0.5° repeatability). Purpose-built, each doing one thing.
• Sailmon — the crossover. The MAX is a multi-band, multi-GNSS receiver (GPS/GLONASS/Galileo/BeiDou, maker-quoted 0.3 m) with a 9-DOF IMU fusion filter driving heel and pitch, on a 320x240 transflective LCD. Uniquely here it ingests NMEA 0183/2000 (wind, speed, depth) over UDP and can repeat an E4 processor — a display and a start tool that also reads the boat's own instruments.
• Tacktick (now Raymarine) — the fluxgate specialist. The Race Master and Micro Compass derive heading from an oil-damped fluxgate sensor over the proprietary MicroNet 2.4 GHz link, solar-powered to the point of being effectively perpetual, on twin dual-side LCDs. Magnetic-only: lag-free heading and shift logic, no positioning.

The comparison

Positioning engine: GNSS channel count, constellations and update rate

For any distance or layline number, the receiver is the foundation. A raw 1 Hz fix is useless at start-line scale — at 6 knots the boat covers roughly 3 m between updates. Velocitek's published spec for the ProStart is a 72-channel, 25 Hz multi-constellation module: 25 Hz drops the inter-fix travel to about 12 cm, and the high channel count shortens time-to-first-fix and improves lock in the multipath-heavy environment right beside a steel committee boat. Sailmon's MAX publishes a multi-band, multi-GNSS engine (GPS, GLONASS, Galileo, BeiDou) with a maker-quoted 0.3 m accuracy; multi-band (tracking two carrier frequencies per satellite) is the more modern approach to rejecting ionospheric error and urban-canyon-style multipath, though Sailmon does not publish an update rate in the same terms Velocitek does, so a direct Hz-for-Hz comparison is not clean. Tacktick sidesteps this axis entirely — the Race Master and Micro Compass carry no GNSS at all, which is exactly why they cannot give distance-to-line. The honest read: both GNSS units are well past the accuracy floor that matters; Velocitek publishes the higher explicit refresh, Sailmon the more modern multi-band front end.

Heading source: fluxgate versus solid-state versus fused IMU

This is the sharpest architectural fork, and it decides shift-calling feel. Tacktick uses an oil-damped fluxgate — a classic magnetometer whose fluid damping mechanically smooths the sea-state jitter before it ever reaches the display. The payoff is a heading that is genuinely lag-free from power-on with no satellite dependence, and a shift readout that is simply the difference between instantaneous heading and a rolling mean course; the trade is that a fluxgate must be kept level and clear of ferrous gear, and heavy damping can lag a genuinely fast knock. Velocitek's solid-state approach differs by product: the Prism samples a magnetic sensor at 44 Hz for ±0.5° published repeatability with digital rather than fluid damping, while the Shift runs a full nine-axis AHRS (magnetometer, gyro, accelerometer) that computes a tilt-compensated heading — so it stays accurate when the boat heels, where a raw fluxgate would error. The ProStart blends its 3-axis geomagnetic sensor with the 100 Hz six-axis IMU, using inertial data to hold heading steady between the 25 Hz GNSS fixes. Sailmon's MAX leans on a 9-DOF IMU fusion filter that the maker states stays stable in rough conditions and additionally resolves heel and pitch. In short: fluxgate for the simplest, most immediate magnetic feel (Tacktick); tilt-compensated solid-state or IMU-fused heading for accuracy under heel and smoothness at speed (Velocitek Shift/ProStart, Sailmon).

Start line: distance-to-line geometry and the bow offset

This is where the GNSS units earn their keep and Tacktick concedes the point. Velocitek's ProStart computes your perpendicular distance to the infinite start line — extend the line through both pinged marks and drop a normal from the boat — and displays it to 0.1 m resolution across the final ±10 m (the -9.9 to 99.9 m window), refreshed twice a second in race mode. The detail that separates it is the bow offset: because the 100 Hz IMU knows the hull's instantaneous heading and heel, the ProStart projects the reading from the antenna to the actual bow you are steering to the line, rather than to wherever the unit is mounted. Velocitek explicitly recommends slow, straight-course pings — even a 25 Hz receiver benefits from a clean geometry at each end. Sailmon's MAX offers the comparable suite — ping both ends, then distance-to-line, line bias and estimated distance-from-line-at-gun — from its multi-band engine, with the added advantage that if wind is fed in over NMEA it can reason about the favoured end from true wind rather than heading alone. Tacktick's Race Master gives a resynchronising countdown timer and a line-bias readout (sail head-to-wind, it tells you which end is favoured), but with no positioning it cannot report distance-to-line — the defining limit of the magnetic architecture. For nailing the boat end to a length, Velocitek and Sailmon; Velocitek's bow-offset geometry is the more explicitly engineered.

Shift tracking: how each defines the mean and the delta

All three answer the same tactical question — headed or lifted versus your mean — but derive it differently. Tacktick's Race Master runs a two-tier display: magnetic heading on the upper line, deviation from the rolling mean course and the size of the shift on the lower, driven by the differential of the fluxgate heading. It is deliberately spare — fewer numbers to parse mid-tack — and the mean auto-updates as conditions settle. Velocitek's solid-state compasses do the same from a cleaner sensor: the Prism/Shift show bold header/lift indication and, on the ProStart, a shift-indicator bar graph where each segment maps to a fixed angular deviation from your initial tack angle, so the trend is visible at a glance. Sailmon's MAX goes furthest analytically — a header/lift indicator plus a logged wind-shift graph trending the oscillation over time, genuinely useful to a tactician building the day's phase picture, and richer still when fed true wind over NMEA. The trade is cognitive load: Tacktick's austerity is a feature under pressure; Sailmon's depth rewards a dedicated set of eyes.

Display: transflective physics and reading through polarised lenses

A tactical display lives or dies on daylight legibility through spray and polarised sunglasses. All three use transflective LCDs — reflecting ambient light rather than fighting the sun with a backlight — which is why they stay readable where a phone screen washes out. Velocitek's ProStart bonds a Gorilla Glass front to a white-on-black transflective panel; the high-contrast segment display is chosen specifically to punch through polarised lenses at any lens axis, and the digits are large enough to read from the rail. Sailmon's MAX carries the most information density — a 320x240, 4.4" transflective LCD with anti-reflection front glass — which buys a graphical, configurable layout at the cost of asking slightly more of the eye than a segment readout; the AR coating is what keeps that pixel display usable in direct sun. Tacktick's Race Master uses twin high-contrast LCDs mounted at the ideal underway viewing angle and readable from both sides of the boat, with large digits and three-level backlighting — engineered for a hiking crew reading across the deck. For the fastest single-number glance, Velocitek and Tacktick; for a rich configurable picture, Sailmon.

Networking, logging and integration

Here the MAX is in a different class. Sailmon's MAX carries WiFi (2.4 GHz), Bluetooth and LTE-M with an integrated SIM for live cloud tracking, ingests NMEA 0183 and 2000 (wind, speed, depth) over a UDP port, can act as an E4 processor repeater, and mirrors to a second MAX in repeater mode — it is a node in the boat's data system, not an island. Velocitek's ProStart is deliberately standalone: it logs position, COG, SOG, magnetic heading and heel at 4 Hz to 8 GB of onboard flash (~1000 hours) for post-race debrief via the Velocitek app over Bluetooth, but it does not read the boat's instruments. Tacktick networks over its own proprietary MicroNet 2.4 GHz mesh — robust and self-contained across the Tacktick range, but a closed ecosystem that does not talk NMEA natively without a bridge, and the compass does not log a track. If you want one screen fused with the boat's wind and speed, only Sailmon does it; if you want a rich track to review, only Velocitek logs one.

Power and endurance

Three different philosophies. Tacktick is the set-and-forget benchmark: the Micro Compass and Race Master are solar-powered with a maker-quoted ~300 hours of autonomy (around 200 hours of run-time from a full charge with no sun), submersible to 10 m and buoyant — effectively perpetual for a season of racing. Velocitek's approach is USB-rechargeable lithium: the ProStart publishes roughly 75-100 hours and charges from any phone charger, while the Shift carries a 900 mAh LiPo rated ~100 hours (60 with backlight) topped up by a 120x27 mm polycrystalline solar panel and a user-replaceable cell, sealed to IPX8 (the Prism likewise IPX8, 3 m/30 min). Sailmon's MAX trades endurance for capability: a 3600 mAh battery gives about 16 hours with everything running — enough for a long race day but the shortest here — recharged by a waterproof inductive pad with no port to corrode. For multi-day regattas without a charging routine, Tacktick; for the richest device that you simply dock overnight, Sailmon; Velocitek sits between with strong logging endurance.

Our take

For distance-to-line at the boat end, Velocitek's ProStart is the most explicitly engineered instrument here: 25 Hz multi-constellation GNSS fused with a 100 Hz IMU, 0.1 m resolution across the final ±10 m, bow-offset projection to the actual bow, and a Gorilla Glass transflective display built to read through polarised lenses — plus 4 Hz logging to 8 GB for debrief. If you want one screen that fuses GNSS start data with the boat's own wind and speed and shares it live, Sailmon's MAX is the only unit that does it — multi-band GNSS, 9-DOF fusion, NMEA 0183/2000 ingest, LTE-M tracking and a 320x240 transflective display — at the cost of ~16 h endurance and more to read. For a maintenance-free magnetic shift reference that is lag-free and effectively never needs charging, Tacktick's fluxgate Race Master remains the durable standard, accepting that it gives you no distance-to-line. On a Melges 40 these are complementary, not competing: the common Grand Prix pairing is a GNSS start computer for the line plus a magnetic compass for the shifts, each working to its architecture.

Who each is best for

• Velocitek — crews who lose ground on the line and want the sharpest GNSS distance-to-line with bow-offset geometry and a 4 Hz track to debrief; the Prism/Shift as a clean solid-state shift compass.
• Sailmon — programmes wanting one integrated screen fusing GNSS start data with NMEA wind/speed/depth, live tracking and heel/pitch, and comfortable managing an overnight charge.
• Tacktick — crews wanting a rugged, solar, lag-free fluxgate shift reference with no charging discipline, where distance-to-line is handled by a separate GNSS tool or not needed.

The takeaway

The choice is really a choice of sensor architecture. Velocitek = a GNSS-plus-IMU start computer, sharpest at perpendicular distance-to-line and post-race logging. Sailmon = a multi-band GNSS crossover that is also a node on the boat's NMEA network. Tacktick = an oil-damped fluxgate that is lag-free and perpetual but blind to position. The more useful question than "which brand" is "which physics do I need — precise distance-to-line, a fused all-in-one, or a maintenance-free magnetic reference?" Our pick: the ProStart if the line is where you lose ground, the MAX if you want one wireless screen fusing GNSS start data with the boat's instruments, and Tacktick if you want a rugged solar fluxgate for the shifts — with a GNSS start computer plus a magnetic compass the strongest all-round pairing on a Grand Prix boat. We will document our actual fit in field reviews. See the racing start explained and race-boat electronics for the wider system.