Compass Variation & Deviation Practice Pack, Swing, A4 PDF
The compass work that decides exam papers and deviation cards, drilled until the ladder needs no thinking: thirty conversion problems, two swings to reduce and a third worked for you, and a key that is right by construction.
Sheet 01: the conversion ladder drawn as a ladder, true to variation to magnetic to deviation to compass, with the direction of application marked both ways, the easterly plus and westerly minus convention, the published mnemonic, a worked example each way and the three errors that cost marks
Sheet 02: thirty generated conversion problems in one ruled table, stratified across all four combinations of easterly and westerly variation and deviation and across both directions, with five that cross 000 degrees so the wrap must be handled properly
Sheet 03: deviation by your own observation, by transit with a labelled plan diagram, by distant object and by amplitude using sin A = sin Dec over cos Lat, with a blank recording form and six practice problems
Sheet 04: a blank swing record on the eight principal headings and an original deviation card in table and curve form, the curve grid drawn ready to plot, with UK and US guidance on how often to swing
Sheet 05: coefficients A to E, each one drawn as its own signature curve, with its cause and its corrector, and Bowditch's proper arithmetic for pulling all five out of a swing
Sheet 06: the worked key to every drill, every bearing problem and both swings, including the extracted coefficients and honest residuals; A4 and US Letter editions included
Conversion is the skill candidates lose most marks on, and it is lost the same way every time: the error applied in the wrong direction, the wrap through 000 dropped, or an error left unnamed so it can never be signed. This pack drills all three out of you. The problems are generated and stratified, so no sign pattern can be guessed, and the answers are computed from the same ground truth that set the questions.
The second half is the practical work. Check a compass against a transit, a distant object or an amplitude; record a swing on the eight principal headings; then reduce it to coefficients A to E and read what the residuals are telling you. The two swings you reduce were built coefficients first, rounded to the half degree an observer can honestly read, then re-extracted from those rounded figures, so the printed residuals are what the rounding leaves and not a fudge.
Every figure is taken from Bowditch and the NGA Handbook of Magnetic Compass Adjustment, both US Government public domain, with carriage from SOLAS V/19, the residual deviation card from IMO Resolution A.382(X) and the UK adjustment triggers from MCA guidance. No table is reproduced from anyone's copyrighted form: the swing record and the deviation card here are original.
What's inside
Cover and how to use
Sheet 01: True to compass and back, the conversion ladder
Sheet 02: Thirty stratified conversion drills
Sheet 03: Checking your own compass, transit, distant object and amplitude
Sheet 04: Swing record and deviation card, table and curve
Sheet 05: Coefficients A to E and two swings to reduce
Sheet 06: Worked answers with coefficients and residuals
Combined pack PDF plus individual sheet PDFs, each in A4 and US Letter
Who it's for: OOW and Master candidates who muddle true, magnetic and compass under exam pressure, RYA Yachtmaster students, and owners and mates who need to swing a compass and produce a deviation card properly.
Licence: Personal and classroom use. You may share and repost this content, including commercially. You may not resell the files themselves or sell them on as a standalone product. Copyright remains with Maritime Master Limited.
Printing: Print at 100%, never fit to page. Sheets 03 and 04 are working forms: print as many copies as you need. Greyscale by design, so it prints cleanly in black and white.
