Chartplotters Compared: Garmin, Raymarine and B&G

This is an objective comparison — we have no partner in this category. Built from published specifications and established engineering, not a hands-on test.

Judged as glass alone, all three flagships are close: full-HD IPS panels, solid-state Doppler radar and multi-constellation GNSS. The real separation is in the sailing layer and the bus it rides on — B&G's Zeus SR builds laylines as a live wind-shift parallelogram and drives its own autopilot to a wind angle; Garmin's GPSMAP 8600 brings the fastest processor and BlueChart/Navionics with Auto Guidance; Raymarine's Axiom 2 Pro is the strongest cruising navigator and the only one that runs C-MAP and Navionics together. For a Melges 40 the plotter is a pre-start and passage tool, not a windward-leeward instrument — but the ecosystem it commits you to defines the whole electronics fit. For the fundamentals see sailing instruments and electronics and what electronics you actually need.

At a glance

The comparison

Processor, operating system and redraw

An MFD is a real-time compositor: it rasterises vector cartography, overlays a radar sweep, decodes camera and sonar streams and paints instrument gauges, all while staying responsive to touch. That is a GPU-and-core problem, and it is where the flagships have quietly pulled apart.

Garmin's GPSMAP 8600 leans on what Garmin calls its most powerful marine processor, and the published claim is the fastest map-drawing in the range — meaningful when you pan a densely-surveyed chart with radar and sonar overlaid. Raymarine's Axiom 2 Pro runs a 6-core processor under LightHouse 4, a Linux-based OS with an app-style home screen and 64 GB of solid-state storage, so chart caching and video handling are generous. B&G's Zeus SR answers with an 8-core processor and a redesigned interface specifically reworked for the sailing panels — the point of the extra cores here is not sonar for anglers but keeping SailSteer, WindPlot and a full chart redraw fluid together. In practice all three are quick; the tie-breaker is which sensor payload you intend to hang off the box.

Display: panel technology, brightness and coatings

Every current flagship has moved to IPS (in-plane switching), which matters on a heeled boat because IPS holds colour and contrast across wide off-axis viewing angles where the older TN panels washed out — B&G quotes 80° in every direction for the Zeus SR's SolarMAX HD panel. Resolution has converged on full-HD 1920×1080 at the larger sizes across all three.

Brightness is where the published numbers diverge and where a cockpit-mounted plotter lives or dies. Raymarine publishes roughly 1300 cd/m² (nits) on the 9" Axiom 2 Pro and ~1200 on the 12"/16", among the brighter figures quoted; B&G cites just under 1200 nits for the Zeus SR. Garmin does not headline a nits figure for the 8600 but specifies a sunlight-readable FHD IPS panel. Two second-order details separate them for a race deck: the coating and the bonding. Raymarine's HydroTough nano-coating actively sheds water, oil and salt so the panel stays legible when it is being hosed with spray — a genuine advantage upwind in a breeze. Optical bonding (the LCD laminated to the cover glass with no air gap) cuts internal reflection and stops condensation forming in the gap; it is standard on these flagship tiers and is the reason they read in glare where cheaper air-gap screens fog and mirror.

Control method is a real divergence, not a preference footnote. Raymarine's HybridTouch and B&G's Zeus SR both back the touchscreen with physical keys and a rotary dial — the rotary especially is what you want when the boat is slamming, gloves are on and a fingertip cannot reliably hit a soft button. A pure-touch MFD is fine at anchor and awkward at 25 knots of boatspeed in a seaway.

Cartography engines — the part that actually differs

The chart is not a picture; it is a queryable vector database with a routing engine on top, and the three brands run three different pipelines. This is the single most consequential difference for a navigator.

Garmin ships BlueChart g3 with integrated Navionics data and Auto Guidance. Since Garmin's acquisition of Navionics the two datasets have been fused, so a Garmin card gives you the vector chart plus Navionics' SonarChart — crowdsourced sonar logs interpolated into high-resolution 1-foot contours by a spline-smoothing algorithm. In heavily-trafficked waters that density is unmatched; Auto Guidance then proposes a route that respects your draught and a safe depth contour.

B&G (and its Navico sibling Lowrance) runs C-MAP, and on the Zeus SR that is the current C-MAP X-Gen / DISCOVER X generation — a rebuilt vector engine with high-resolution shaded-relief bathymetry, custom depth shading and Easy Routing, which is subscription-free. C-MAP's edge is offshore: its bathymetry is professionally maintained rather than crowd-derived, so structure and contours tend to be more trustworthy in remote or deep water where Navionics' user-sourced model thins out.

Raymarine is the neutral platform and for many navigators that is the killer feature. Its own LightHouse charts are free and download by region, and the Axiom reads both C-MAP and Navionics cards natively — so you are not married to one survey. For a campaign that sails offshore in one region and inshore in another, running the better-surveyed card in each area is a real, defensible advantage no single-vendor plotter can match.

The sailing layer — where B&G is a different class of tool

This is the reason a sailing programme buys B&G, and it is not marketing gloss — it is a stack of specific algorithms fed off the sailing instruments.

SailSteer is the centrepiece. Rather than drawing a naive straight rhumb-line to the mark, it computes and renders a layline parallelogram from live true wind direction (TWD), heading (HDG) and course over ground (COG): the green and red dashed lines are your target TWA on each tack, the sectors show how the laylines are swinging with the shifts, a central arrow shows tidal set and drift, and rudder angle sits at the base. Critically the laylines can be set to fold tide in automatically and to use either a manual target TWA or measured TWA — so the layline you see is the geographic layline (through the water and over the ground), not the textbook 45° a plotter without wind and tide inputs would draw. That is the difference between a call that puts you on the mark and one that leaves you short in a foul tide.

StartLine builds a start from a two-end ping — favour ("ping" the boat and pin) and the MFD returns distance-to-line, line bias (which end pays and by how many degrees) and burn time / time-to-burn against the countdown, so you can run the line knowing whether you will be early or late. RaceTimer is a synchronisable countdown that can be reset to the gun on the whole network at once. WindPlot / Advanced WindPlot logs TWD and TWS over time so you can read the oscillation period and mean of a shifty breeze and decide whether to sail the header or bank the lift.

Then the loop closes at the autopilot: the Zeus SR is the head unit for a B&G NAC-series computer (NAC-2/NAC-3), and B&G's pilots can steer to a wind angle — hold a TWA rather than a compass heading — using the same wind data that draws the laylines. Garmin (Reactor/GHC) and Raymarine (Evolution/ACU) both make excellent pilots with wind-vane modes, but the tactical-display-to-pilot integration is tightest, and most sailing-native, in the B&G world.

Garmin and Raymarine are not empty here — both draw laylines, show wind data and carry a race/start timer, and Raymarine's LightHouse has a competent Sailing dashboard. But on those platforms sailing is one app among many aimed largely at power and fishing boats, whereas on B&G the entire UI, and the extra processor headroom, exists to serve it. See the B&G research note.

GNSS: update rate is the spec that matters afloat

For navigation any modern receiver fixes to a metre or two; for a race boat the number that matters is update rate, because COG and SOG derived from position are only as smooth as the fix is frequent. B&G's Zeus SR integrates a 10 Hz receiver tracking GPS, GLONASS, Galileo, BeiDou and QZSS with SBAS (WAAS) — ten fixes a second means COG/SOG that keep up with a boat swinging through a tack, and cleaner ground-referenced laylines. Garmin and Raymarine both run high-rate multi-constellation receivers (Raymarine publishes tracking of 28 satellites across GPS/Galileo/GLONASS/BeiDou); multi-constellation matters under a rig and boom that mask part of the sky, where a single-constellation receiver loses satellites and the fix degrades. For sub-metre work all three can take an external RTK/heading source over the network, but the built-in 10 Hz sailing-tuned front end is a B&G habit worth noting.

Radar: solid-state Doppler, and why weight aloft decides it

All three flagships have moved off the old magnetron to solid-state pulse-compression radar with Doppler target colouring — which paints closing targets one colour and opening/stationary ones another, so a ship on a collision course is obvious at a glance. The engineering trade-offs are real and specific.

Garmin's Fantom 18x dome outputs a published 50 W — the most powerful 18" solid-state dome quoted — and offers dual-range (a close and a long range painted at once). That power buys open-water range and target definition offshore. Simrad/Navico's Halo-class domes (the natural B&G pairing) run about 25 W, also dual-range, and are well regarded for close-in detail and their bird-mode. Raymarine's Quantum 2 outputs a published 20 W — the lowest of the three on paper — but its trump card on a sailing yacht is mass and installation: the dome weighs roughly 3.5 kg (about 3.5 lb in Raymarine's figure) and offers a Wi-Fi link, so it goes up a backstay or mast bracket with a single power cable and the least weight aloft. On a boat where every kilogram at the first spreader hurts stability and pitch, the lightest dome with a wireless data path is a stronger argument than raw watts. Raymarine is also noted for the clearest visual change when Doppler mode engages. For a Grand Prix keelboat the honest ranking is: most watts and offshore reach → Garmin; least weight aloft and simplest install → Raymarine; balanced close-range detail within a Navico fit → Halo/B&G.

Networking and the instrument backbone

The plotter is the head of a network, and the backbone decides how cleanly everything talks. All three use NMEA 2000 (Garmin badges it NMEA 2000, Raymarine as SeaTalkng, B&G/Navico as SimNet — all electrically NMEA 2000) for instruments, GNSS and pilot, with LEN-rated power budgeting (Garmin's 8600 draws LEN 2). High-bandwidth traffic — radar, sonar, cameras, chart sync between MFDs — rides a separate Ethernet layer: Raymarine's RayNet and B&G's Zeus SR both provide gigabit links, and the Zeus SR adds Wi-Fi 5 and Bluetooth for app control and phone mirroring. The practical rule is unchanged and worth stating plainly for anyone speccing a fit: instruments, autopilot and sensors talk cleanest inside one badge because they share firmware, calibration tables and damping models. Cross-brand over NMEA 2000 works for standard PGNs (position, wind, depth, AIS) but you routinely lose the proprietary extras — a Garmin plotter will not surface B&G's SailSteer, and a B&G head will not drive Garmin's autopilot to a wind angle. Commit to the ecosystem, not just the screen.

Our take

With no partner here, the objective read: for a boat whose primary job is racing — a Melges 40 among them — B&G's Zeus SR is the correct plotter, not because its cartography or radar beats the others (they trade blows) but because the sailing layer is a genuinely different class of instrument: laylines computed as a live wind-shift parallelogram with tide folded in, StartLine bias and burn-time off a two-end ping, and a chartplotter that is the head of a wind-steering autopilot. For a cruising boat that wants the fastest processor, the deepest crowdsourced inshore cartography and the most powerful dome, Garmin's GPSMAP 8600 is hard to beat. For a navigator who values flexibility — running C-MAP and Navionics side by side, the brightest coated panel, and a clean LightHouse 4 interface — Raymarine's Axiom 2 Pro is the pick. And for pure closed-course work, remember the plotter recedes behind the instruments: spend on the wind and speed sensors and their displays first (see race-boat electronics), then let your offshore and start-line ambitions choose the MFD.

Who each is best for

• Garmin GPSMAP 8600 — cruisers and dual-purpose boats wanting the fastest redraw, BlueChart/Navionics with Auto Guidance and the highest-output Fantom radar for offshore reach.
• Raymarine Axiom 2 Pro — navigators who want dual C-MAP + Navionics cartography, the brightest HydroTough-coated panel and the lightest radar dome aloft, on a polished LightHouse 4 platform.
• B&G Zeus SR — racing and performance sailing boats that want SailSteer laylines, StartLine, WindPlot and a chartplotter wired to a wind-steering NAC autopilot.

The takeaway

The three flagships have converged on the hardware that used to separate them — full-HD IPS glass, solid-state Doppler radar, multi-constellation GNSS — so the decision has moved up the stack to software and integration. Garmin owns the processor and the fused Navionics cartography; Raymarine owns cartographic neutrality and panel brightness; B&G owns the sailing algorithms and the autopilot loop. The sharper question than "which brand" is "how much does the chart page do for how I sail": around the cans, little — the instruments win, so buy those first; on a start line and offshore, a great deal — so weigh the layline maths, the routing engine and the weight of the radar aloft. Match the plotter to the ecosystem it will live in, and we will document our actual fit in a field review. See sailing instruments and electronics for the wider picture.

Our pick: for a Grand Prix sailing boat, B&G's Zeus SR — its SailSteer layline maths, StartLine and wind-steering autopilot integration make it a genuinely different tool for racing. Choose Garmin's GPSMAP 8600 for a cruiser wanting the fastest processor, Navionics-fused cartography and the most powerful radar; choose Raymarine's Axiom 2 Pro for dual-cartography flexibility, the brightest coated panel and the lightest dome aloft. For pure closed-course racing, spend on the core instruments first and treat the plotter as a pre-start and passage tool.