NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Time on a small boat CN
From: Jim Thompson
Date: 2004 Jan 8, 15:12 -0400
From: Jim Thompson
Date: 2004 Jan 8, 15:12 -0400
I also use an Excel spreadsheet. So far I use these columns (one observation date per row -- I check every week or 10 days or so): Say the first date is in row 3 and the third date is in row 5: A5 Date of observation in date format. B5 Number of seconds that watch is fast (+) or slow (-). C5 Elapsed # days since first observation = A5-$A$3. D5 Error rate in seconds per day = B5/C5. E5 Mean error in seconds/week = D5*7. (You could calculate that per month, whatever). So the Excel graph could show C5 on the X axis, and either D5 or E5 on the Y axis. The graph shows at a glance whether the rate of change of watch error is linear or not, and if it is linear, then the rate of change would be D5 or an average of D5. I can email the spreadsheet to anyone. Perhaps others have suggestions for refining this method. Jim Thompson jim2@jimthompson.net www.jimthompson.net Outgoing mail scanned by Norton Antivirus ----------------------------------------- > -----Original Message----- > From: Navigation Mailing List > [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM]On Behalf Of RHT - > travelling > > I just use a spreadsheet, providing one row for each day. On days when I > compare the wristwatch to WWV, I note the error and enter it in the > appropriate column. In my case, the date is in Column A, the error for my > wristwatch is is column B (about every 30 days, although there's nothing > stopping you from entering a reading every day), and the error > for the watch > that is in my nav kit is in column C. I use + error numbers to indicate a > watch that's running fast and - error numbers to indicate a watch that is > running slowly. The reason for including all the dates is that when I ask > Excel to make the graph, it needs to know how far apart in time the error > measurements are. I also have Excel print the "best straight line" for the > data points. > > > -----Original Message----- > > From: Navigation Mailing List > > [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM]On Behalf Of The Martins > > > > How do you do an "error plot"? I'd like to rate my own watch for a > > transatlantic passage (Newfoundland to Ireland) this July.
