GL: Odometer question

[Kendall Caputo]

Ron and Molly:

First of all your GPS is probably measuring in Nautical Mile while the river
is measured in Statute Miles.
55 miles x 5280 feet = 290,400 feet
53.8 x 6000 feet = 322,800 feet 
So you were actually off by 6.1 Statute Miles (320,800- 290,400 = 32,400/
5,280)
That is an 11% discrepancy.  

Possible contributors:
You don't steer a straight line but rather zigzag the course
You did not take into account getting in and out of you berth or anchorage
The mile markers may not be perfectly accurate.

One other thing.  I am not familiar with Ray Marine products but if you
odometer is calculated using a paddle wheel on the hull instead of by
Satellite positioning then any current would also be a contributing factor.

Ken


Message: 5
Date: Fri, 14 Sep 2007 21:28:59 EDT
From: Bodie6413 at aol.com
Subject: GL: Question
To: great-loop at lists.samurai.com, MTOA-Listserv at yahoogroups.com
Message-ID: <be9.1c4df325.341c8f5b at aol.com>
Content-Type: text/plain; charset="us-ascii"

A question for the expert navigators out there.  We have been  experiencing
a 
discrepancy in our routing in that today we went from mile marker  288 to
233 
on the Illinois River, a mile marker distance of 55 miles.  Our  odometer 
function on the GPS (Ray Marine C-120) tells us at the end of the day  we 
completed 53.8 miles or a difference of 1.8 miles.  Any ideas of where  the
extra 
mileage is going????  

Ron and Molly  on Colonel's Lady, 1986 43' Heritage East, MTOA #2950, AGLCA 
#3460, San Diego, bodie6413 at aol.com




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