Hydrographic survey simulator — run multibeam lines on a survey catamaran, in the browser

A survey line is only worth logging if the vessel stays on it, at the right speed, without rolling or swinging the swath to pieces. On a real boat that costs ship time and fuel to learn. SkipperCheck's marine simulator has a survey unit of its own: the 24 m survey catamaran LOTE, a multibeam in her moon pool, AUTO TRACK on her DP panel, planned lines in two real places, a sound velocity cast on station and judged exercises that score every ping. You can do it now in the browser, on your phone too.

What it trains

The ≋ SURVEY button (beside ⛽ OFFSHORE) opens SURVEY PRACTICE.

• Holding a survey line. The XTE bar in the survey panel shows how far she is off the line, with a ±2 m band in green. The multibeam only logs while she is on a planned line with the ram down; pings outside the band cost score.
• AUTO TRACK. She follows the planned line she is lined up on at a set speed over the ground. ↑ ↓ set the speed in 0.1 kn steps, ← → offset the line 1 m, M puts her back on it; the lever, the wheel or V take over.
• A line by hand — the crab angle. Exercise 2 forbids AUTO TRACK: you run line 2 with the wheel, the autopilot's heading or AUTO HDG, steering up into the wind and current until her course over the ground lies along the line. At survey speed the bow tunnel has no grip; she steers with her azimuths and crabs.
• The racetrack. Four lines in the order 1, 3, 2, 4, AUTO TRACK on the lines, the turns by hand. No holidays, 10 % overlap or more.
• Reading the swath. The multibeam on the ram (MBES ▼: ram down, 8 kn at most) sweeps about 3.5 × the depth. It is drawn on the docking plan as a depth mosaic and on the chart, with the overlap between neighbouring lines and the gaps — the holidays.
• Data quality. A ping is flagged when she rolls past 4°, swings faster than 1.5°/s, runs outside 4–6 kn, or has no sound-velocity profile loaded; the chips (ROLL, YAW, SPEED, SVP) tell you which.
• Which way to run in a sea. Exercise 4 asks first: along the contours with the sea on her beam, or into and with it? The wrong answer costs 30 points.
• The sound velocity cast. SV CAST: stop on AUTO POS at the orange ring; the probe goes down from the A-frame and back. Hold her within 3 m, the wire under 15°. A vessel held against a current shows a little wire angle; one drifting with it keeps the wire upright but loses her position.
• Line planning in depth. Kaštela Bay's three lines lie 80 m apart in 33 m — a swath of about 100 m — and the cast comes first: lines logged before it lose 15 points.
• Scoring and the debrief. A score out of 100 (★★★ from 90, ★★ from 75) and a debrief: the share of pings within ±2 m, XTE RMS and max, good pings by flag, coverage and holidays, the overlap of each pair, whether the training target C1 was found, the cast — and one tip.
• ▶ DEMO — watch the surveyor first. Every judged exercise can be sailed by a demo surveyor. Each order goes through the real control, ringed in orange — LEVERS / AUTO TRACK / AUTO POS, the lever, the autopilot's heading, MBES ▼, SV CAST — and the DEMO bar says the order and why. Pause, ×½ ×1 ×2, NEXT order, or touch a control and take over; at the end, ▶ YOUR TURN. His score is shown, never kept.

The idea

A survey vessel is not a yacht with a sonar bolted on, so we built one from the keel up. LOTE is our own design: two slim aluminium hulls 7.2 m apart, the moon pool amidships, the survey lab and wheelhouse forward, an orange A-frame over the stern for the sound velocity probe, two GNSS antennas on a bar for her heading.

Her DP panel is our platform supply vessel's — the same joystick, AUTO HDG and AUTO POS — with one mode a surveyor needs: AUTO TRACK, which holds a line over the ground, carries her crab angle against wind and current and holds the set speed. It follows one line, not a route; the turns are yours. The turn is where a survey goes wrong, so the turn is what you practise.

The multibeam is a coverage model built for training, not a beam-by-beam sonar: each ping lays a swath from the depth under her and either side, cut when the data would be bad — the outer beams for roll, the outside of a turn for yaw, only ±45° without a profile. The limits (±2 m, 4–6 kn, 4°, 1.5°/s) are this course's training figures. The seabed in both boxes and the 6–7 m training target C1 are ours, built inside the charted depth classes and labelled as such on the chart; the sound velocities come from a published formula for the season's water.

While she logs, casts or holds station on AUTO POS she is a vessel restricted in her ability to manoeuvre: red-white-red by night, ball-diamond-ball by day, as Rule 27(b) asks.

The vessels you do it on

The survey unit belongs to one vessel: LOTE, 24.0 × 9.6 m, 1.6 m draught (2.1 m with the transducer lowered), about 95 t. Two 360° azimuth thrusters under her sterns, about 300 kW and 46 kN each; a 15 kN bow tunnel thruster; 11 kn flat out. V cycles LEVERS (the lever is both azimuths, the wheel turns them ±35°, Q / E the bow tunnel), AUTO TRACK, JOYSTICK, AUTO HDG and AUTO POS.

Her offshore sisters show the differences. The PSV, an 80 m platform supply vessel, has the same DP panel but no AUTO TRACK; her exercises are the 500 m zone, cargo lifts on DP and a drive-off. The CTV, a 26 m crew transfer catamaran on two waterjets, pushes on to a turbine's landing. LOTE is lighter than the PSV, quick to roll beam-on to a sea — exactly what flags her pings — and she alone carries a transducer that limits her to 8 kn the moment it is down. The other 19 vessels, from the Optimist and the sea kayak to ELEONORA, LATEKO, the Namejs catamaran, the tanker and the cruise ship, are in the same VESSEL menu.

The sea is real

SURVEY PRACTICE runs in two real places: a box about 1 NM off the Jūrmala shore in the Gulf of Riga (12–13 m, four lines along the contours 28 m apart, 400 m long) and Kaštela Bay in Central Dalmatia, north of Split (33 m, three lines 80 m apart, 500 m long). Each judged exercise sets its own wind, sea and current — the same for everyone — then the real weather comes back. Free practice in both boxes (6 lines off Jūrmala, 5 in Kaštela Bay, the cast first) runs in today's real weather with no judge.

Outside the exercises LOTE sails in Free Mode: the Gulf of Riga in full detail, the whole Baltic beyond it, any Baltic harbour from the AREA picker (about 2,000 of them), and Central Dalmatia as a second sea. The sky is real, and the weather is MET Norway's real forecast: wind, cloud, rain, snow, fog and the visibility they leave. The sea state builds with the wind; the current runs, and her hull feels it — STW against SOG, COG against heading. Radar, AIS targets, the OpenSeaMap chart with EMODnet depths, a CPA plotter and traffic that follows the COLREGs are all there, by day and by night.

Shared sea — other real people on the water

Logged in, SHARED SEA is on by default — one live sea for everyone at ×1 — and you can switch it off. In Free Mode you meet other skippers' boats on the radar, on the chart and through the bridge window; it works in Croatia too. A judged survey exercise is run alone, with its own conditions, so the scored line is yours.

Classroom and the scenario builder

🎓 CLASSROOM → TEACH opens a private class: a name and what the class sails — FREE SAILING, a SCENARIO, a DOCKING LESSON or a DRILL, and survey is on the drill list beside man overboard, distress signals, pilot transfers, offshore and towage. OPEN THE CLASS gives a code (like K7QM-2XPA) and a link; up to 30 students at a time, from any browser, in the class's own private sea. The instructor sees every boat with her track, speed, heading, CPA and score, can pause everyone, message, inject fog or a wind change or fail an engine; ▤ SUMMARY goes out as CSV or print.

With ✎ SCENARIO BUILDER an instructor builds an exercise of her own: LOTE as the own vessel, under way or made fast; any harbour of the Gulf of Riga or the Baltic; the time and date; wind, visibility, rain and sea state; other vessels with their lights, shapes and Rule 18 status, routes, areas and triggers. ⇗ MAKE A LINK packs the whole scenario into the link itself — nothing is stored on our server — ready to ▶ RUN. TEACH is the instructor's and comes with the subscription; students run shared scenarios for free.

Who it is for

Professional and leisure alike. The cadet before the first watch, the deck officer, the pilot, the tug, offshore or survey crew, the training centre that wants a situation every student can repeat — and, on the same sea, the leisure skipper who is curious how the working boats are handled and what the ship on the horizon can and cannot do. The vessel, the sea and the rules are the same for everyone; only the exercises are the professional's.

How to start

Free Mode is open to everyone — no account needed — with the 15 m motor yacht and the 50 ft cruiser LATEKO LATEKO at up to TIME ×10. LOTE, every other vessel, SURVEY PRACTICE, the scenario builder and Classroom TEACH come with the simulator subscription; students join shared scenarios free. SHARED SEA and the regatta need a free SkipperCheck login. For yacht skippers the main product is the VHF course (€199, /vhf-course) — "Charter Ready": the VHF certificate and simulator practice together.

When the lines are done there is the regatta next door: THE BALTIC LAP, identical ELEONORAs racing a lap round the whole Baltic in real time, every mark a real port or cape with its own story told on the mark cards as you round it. It is the first of many laps; the next will be somewhere else in the world.

FAQ

Does AUTO TRACK make the line turns for me?

No. It holds one line and the set speed; the turns are yours by hand. The racetrack order (1, 3, 2, 4) gives you a full line's width to make each one.

What happens if I run the multibeam too fast?

Over 8 kn through the water the ram is raised, and in an exercise it costs 10 points. Pings outside 4–6 kn are flagged for speed in any case.

Why does the cast come first in Kaštela Bay?

Without a sound-velocity profile only the inner beams (±45°) are kept. Lines logged before the cast lose 15 points and have their outer beams flagged.

Is the seabed real?

The boxes sit inside the real charted depth classes, but the detailed seabed and the training target C1 are ours, and labelled as such. The sound velocities come from a formula for the season, not a measured profile.

Can I run it on a phone?

Yes; the survey panel's buttons stand in for the keys.

Start surveying

Open the simulator, pick LOTE under VESSEL, press ≋ SURVEY and let the demo surveyor run the first line — then run it yourself: /colreg-simulator.

Related reading

• Offshore simulator — PSV dynamic positioning at a platform and CTV push-on transfers at a wind turbine, in the browser
• "Chart plotter (ECDIS) simulator — plan a passage on real depths, then prove it for your boat, in the browser"
• Survey catamaran simulator — multibeam lines, the SV cast and DP track-keeping, in the browser
• All articles · Open the simulator

Boat types are described generically; SkipperCheck is not affiliated with any boat builder or class association.