bounding the observer field of vision at sea
ERROR OF PERPENDICULARITY
in addition there are some non-adjustable erroes
graduation error,shade error,optical error, prismatic error,telescopic error
Sextant Errors are of 2 Types:
1) Adjustable error,
2) Non Adjustable errors
a)error of perpendicularity,
d)Error of collimination
2)Non adjustable Errors:
ATMOSPHRIC PRESSURE DECRSIN
using instruments like sextant..with some simple navigational calculations...
if the cpa matters , and collision cant be avoided by the give way vsl alone then i will alter other wise , maintain co and speed.
take the series of brg if risk of collision does not exist the maintain co and speed if roc exist the i will give five sort and rapid blast, check nav lights, inform master,inform engine room,put helms men and still she is not taking an action then one short blasta/co to stbd if depth available or reduce speed
BY A FIXED OBJECT OR A SHARP BEND
velocity of propagation in water, stylus speed error, pythagoras error, multiple echoes, thermal and density layers, zero line adjustment error, cross noise, Aeration.
Tropical Revolving Storms which forms in Tropical regions. Northern hemisphere it moves towards north and vice versa in Southern hemisphere.
raster chart is the photo copy of the paper chart,vector chart is electronic form of chart