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» Online Classroom   »   » Public Discussion of Inland and Coastal Navigation   » Need for Light List to Chart conversion?

   
Author Topic: Need for Light List to Chart conversion?
John Thompson


 - posted November 05, 2004 03:09 PM      Profile for John Thompson           Edit/Delete Post 
In the 4th to last paragraph in section 12.1 it mentions that the Light List gives data in decimal minutes. The paragraph also states large charts deliniate into seconds. Soo.., in reference to problem 1-15 I am wondering about my measured position of the bouy vs. the Light List position. Since there are 10 demarcations per minute, do each equal 6 seconds? What do I do with the following...
My measurements from chart of Y "PA"
123 27 8(graduations) W
48 12 3(graduations) N
those graduations representing either 6 seconds or tenths of a minute?
Light List position
123 28 41 W
48 12 54 N
the last field representing decimal minutes?

David Burch


 - posted November 05, 2004 06:02 PM      Profile for David Burch           Edit/Delete Post 
which light list are you reading from? the one in the text materials (copy i have ) is in deg min tenths, whereas it looks like you have in the LL example deg min sec.

you can interpret the tick marks (divisions) on the chart by counting the divisions and dividing that into the interval. if there are for example 10 divisions between 48' and 47' then each division is 0.1' which is the same as 6".

The values you give:
123 28 41 W = 123° 28' + (41/60)' = 123° 28.68'
48 12 54 N = 48° 12' + (54/60)' = 48° 12.90'

which appears to be from a newer LL that shows more specific locations.... although these locations are not at all that precise as buoy positions can shift around quite a bit.

Reference = Prob 1-15.

From: Starpath, Seattle, WA


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