The Plotting Sheet

I’d read about Plotting Sheets briefly on the online course and while the three instruction books I had on board each touched on the plotting sheet, there seemed to be some assumed knowledge here that I didn’t have.  The idiot me could not find a basic step by step instruction guide.  The sheets themselves did come with some basic instruction, but it didn’t quite fit with what I was trying to achieve.

 

It turned out that the huge gaping hole in my knowledge was transferred position lines, yes I must confess I thus far in my maritime career and never used or even thought about transferred position lines.  

 

I hear the navigators among you despairing, and trust me I was despairing for days, how could something that I felt sure was so simple elude me for so long.  At this point we have been at sea for eight days and I had done nothing but study and keep my watches of course, but even my night watches I spent more time staring at Sky TV than the empty horizon, I was possibly going slightly mad at this point.

 

Back to that infernal question “where on that line are we?” Finally the answer comes to me in the only really valuable bit of online course printing I’d done.  And there it is in black and white staring at me on the page “We move our estimated position to the closest point of the position line”.  Of course, of course, of course we do, of course it was so simple too.

 

Now I see, move the morning EP to the morning position line, draw our noon latitude on the plotting sheet, draw our track from the morning EP, move our position line down our track taking distance run from the log…. And there is it… the position line meets the noon latitude line and bingo, we have an actual fix which compares closely to where we are!!

 

To give real confirmation of this fix I can take an afternoon sun sight, again more maths, graphs, tables and calculations and I get another sensible position line on the plotting sheet.  I then move this back up the course line by the estimated 20 miles travelled and hey presto I now have a cocked hat triangle which puts us within 5 miles of GPS in latitude and longitude at noon.  Admittedly it is now around 1700, but it seems my days of despair and torment are over I finally have cracked this – YES!!!! I have been eight days at sea now, thinking of little else.   And there is it, a curtain has lifted and I see how simple the concept actually is, once you cut through all the jargon and endless books of numbers the process is pretty straightforward and with practice can only get easier.

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