I understand this conversation has gone into more of a new age technological discussion than my initial understanding of the posted question. That being said there have been several postings referring to old school navigation
techniques. I do not know the backgrounds of of the people posting
but have received a few messages regarding boat deviation. It is in reference to these that I again participate in this conversation.
Without use of chart plotters and relying solely upon charts
, coastal pilots ( etc..) and compass. There is a simple mathematical formula to calculate heading. There is an acronym to help remember this formula.
It is :
true virgins make dull companions:
T= true ( you ascertain this by utilizing your chart and compass rose)
V = variation. You can find the annual variation on your chart. It normally is defined in degrees per annum, whether it is plus or minus depends on whether you are sailing west to east or east to west.
M= stands for magnetic, you can either find this on your compass rose of paper charts
, labeled such or by using the formula above.
D= deviation- this is the magnetic interference
of the electronics
on your boat. This may include: antennas, ssb
, radios etc that are in close proximity to your compass and sometimes structural interference
. Keep in mind that new age technologies which will affect them are :!iPods, iPads I phones or any other new technology that has a location device. To test this simply place any of these questionable devices next to your compass and see what happens.
Further more an incorrect grounding wire has the potential to affect your compass reading. Back on point however: every boat has a deviation: I personally do not know how to determine this but any sound surveyor
C= course over ground. This takes into consideration all if the above; not reliant in gps.
Also remember and someone can correct me if I am wrong ... During war time most GPS systems are altered up to 3-4 degrees. ( and all you saltines understand that a discrepancy of only 1 degree over several days to weeks will and can effectually lead you hundreds of miles off course). You will recognize this those of you who know you were in a channel or anchorage yet your chart plotter indicates you are on land.
There is nothing wrong with electronics
, I use them. However, they are known to fail: lightening strikes, salt water
failure :any and all if these things can and if you are out there long enough will happen.
Educate yourself because in the end a computer will not deliver you safely to shore, your knowledge and your Response to emergent situations will.
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