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Old 04-04-2010, 07:32   #1
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Plotting Position

For those who like to record their position, in case of GPS failure, but rarely actually plot this position on paper charts . I have found it useful to record the GPS position as a distance and bearing to a known waypoint (usually the destination). I feel this is better than recording lat and long for several reasons.
There is less numbers so less chance of making an error.
The numbers “make sense” so less chance of making an error
The numbers can be recorded once an hour, but are easy to remember at more frequent intervals.
In short it is much more useful and easy to relate to when our destination is 200.5nm away at 95 degrees than that we are at 41.10.65N 09.21.77E. In the event of a GPS falure the former position is accurate enough for the dead reckoning or celestial navigation that will follow. I am also likely to remember that we had dropped to 195nm to go just before the GPS went blank.
I am sure others must use this method, but everyone I have ever sailed with always records lat and long even when not plotting the position.
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Old 04-04-2010, 07:49   #2
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Thanks.

This may be a useful alternative to plotting a fix on a paper chart; but, then, I don’t find doing it right all that onerous.

When one plots a “fix” on a paper chart, and given time & interest, we can add numerical lat/lon coordinates, ranges and bearings, etc - all of which become very inuitive sources of useful information.
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Old 04-04-2010, 07:52   #3
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I do exactly what you mention for short jaunts like crossing the gulf stream or heading across the Bahama banks. I think for real passage making I'd be recording the latitude and longitude daily.

As you said, I'm usually on a known course line so the only changing variable is the distance. If the GPS should ever fail, all I need to do is plot the course line and distance at the last recorded time and DR from there.
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Old 04-04-2010, 18:17   #4
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remember that the whole reason you are recording your position is that you or others can retrace your steps and try to find you. If anyone can figure it out, you can do what pleases you. I stick to convention just so others can quickly consult the log book and figure out what I am doing...
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Old 05-04-2010, 02:50   #5
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Thanks everone for you comments

Quote:
Originally Posted by s/v Beth View Post
remember that the whole reason you are recording your position is that you or others can retrace your steps and try to find you..
Sorry I don’t quite follow why I would want to "recording a position so that others can retrace you steps”

The reason for recording my position is to provide a stating point for DR or Celestial in the unlikely event of a GPS failure.


If you plot your position on a paper chart you have the added benefit of deriving information from that chart. In this case recording a Lat and long is easier, but in many situations plotting on a paper chart is not done (never done by many skippers) and this is where a bearing and distance is superior."
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Old 05-04-2010, 03:04   #6
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I gave up plotting on the charts when I started getting so many lines on them that it bacame confusing. I guess that's a down side to cruising the same waters often. When off shore we log position at least once per watch (about every three hours). It gives us a permanent record and should I need to resort to DR I have the data to start plotting.
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