Made by code, checked by code, explained step by step

Every problem has a number

A problem is generated from its skill and a number between 1 and 999,999 (its seed). The same number always gives the same problem, so a link to it, a Plot Log entry and a worksheet all open the same problem again. Positions are checked to lie in open water, and tracks are checked to stay clear of land.

Answers are worked from what you were given

Bearings are given in whole degrees and distances to a tenth of a mile, the way a logbook gives them. The checker works the answer from those rounded numbers, not from a hidden exact position, so a careful plot lands on the checker's answer.

Tolerances

Plotting with dividers and a parallel rule is good to about a degree and a tenth of a mile, so chart answers count as right within 2° and 0.15 nm (or 4 % of a long distance); set, drift and course to steer have a little more room because they build on measured lines. Compass conversions must be exact. Every result says how far off you were and what was allowed.

The dividers on the chart

Drag on the chart to measure. A drag that starts on a charted object or buoy snaps to it. The readout gives the true bearing, the magnetic bearing (7°W, the rose's invented variation) and the distance. It runs in your browser only.

What it leaves out

No tides, no leeway, no compass deviation cards, no chart datum, no latitude and longitude, no electronic navigation. The chart is invented: Heron Sound, its lights and its soundings do not exist. Plotroom is practice, not instruction and not a qualification.

The Plot Log

Start one from any checked problem or from the Plot Log page. It lives at a private link (keep it like a key: anyone with it can open, change and delete the log). It shows each skill's attempts, how many were right, your last ten, and which skill to practise next.