DR Sailing Flashcards
What is DR sailing
determining a ship’s approximate position by applying from it’s last known position, a vector or series of consecutive vectors representing the run that has since been made, using only courses steered and distance run
How can you get a fix
soundings, vertical and horizontal
angles, bearings, and ranges
Heading (SH)
direction in which a vessel points at any instant, Ships Head
Course (C)
direction in which a vessel is to be steered, or is being steered
Speed (S)
engine ordered rate of travel
How do you measure course made good and speed made
measured fix to fix
How many LOPs do you need to get a fix
2
What is a running fix
position determined by the intersection of two (or more) LOP’s established at different times
Estimated position
The most probable position of a vessel based upon available information or information of questionable accuracy
What is the most accurate LOP
observing two or more objects in a line or visual ranges
What should you do if there is ambiguity in the LOP taken for a fix
assume vessel is in worse position possible and make recommendation accordingly
If two LOPs are used how far apart should they be
90 degrees
If three LOPs are used for a fix how far apart should they be
120 degrees
What size chart should you plot your DR
Largest scale chart available
In restricted waters how often do you get a fix
Every three minutes
In less restricted waters how often do you get a fix
Every 15 minutes
For how long can you use a LOP for a running fix
30 minutes or less
What is the secret to success for dead reckoning
practice and neatness
What do you need if you want to figure out when a light will be lost from site
computed visibility
What is the maximum distance a light can be seem in the meteorological conditions in immediate vicinity
Computed visability
What is nominal range
maximum distance a light can be seem in clear weather
what does the light list have
information for lights and buoys in US
What does list of lights have
information for lights and buoys in international/foreign waters
What is the three minute rule
distance traveled in yards in three minutes
ships speed in knots x 100
What is the 6 minute rule
distance traveled in miles in 6 minutes
What is a paper computer
Logarithmic speed time distance scale
What is a nautical slide ruler
inexpensive plastic device used for rapid solution for time speed distance problems
Six rules for dr plotting
plotted hour on the hour
every course change
every speed change
every fix or running fix
if single line of position is obtained
new course line plotted for fix or running fix
How many intervals will you extend a DR or course line
two fix intervals
What is an EP considered
midway between a good running fix and a unsubstantiated DR position
Dangers bearing ahead and to the left of the track are labeled? and the right?
NMT
NLT
If you do not have a sextant what else can you use to get an angle
position finder
How often do you check your gyro error
once daily
What can a single LOP provide
Cannot provide position but can give useful negative information
