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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Weighted least squares
From: Peter Fogg
Date: 2010 Dec 19, 09:46 +1100
From: Peter Fogg
Date: 2010 Dec 19, 09:46 +1100
P H wrote:
One of the ways apparent outliers are created is by the mis-recording of time. Its easy enough to do and just as likely to occur as writing down the incorrect altitude. I know this because I've done both, and have also been affected by this vice when using a scribe to record observation data. Since one number looks so like another this error may not be picked up during an averaging or linear-fit exercise. However, if you graph those sights and compare them with the calculated (= true) slope, then such outliers immediately jump out and loudly exclaim: "Hey, look at me! Why do I stand out? Hey! What's going on here?"
Notwithstanding this, your spreadsheet solution appears ingenious. Of course, it presupposes having a spreadsheet to hand. Comparison of slope with sights is not dependent on any electronics, since the slope can be derived graphically.
The attached spreadsheet provides one way for averaging of sights. Observation times go into column A and are considered exact.
One of the ways apparent outliers are created is by the mis-recording of time. Its easy enough to do and just as likely to occur as writing down the incorrect altitude. I know this because I've done both, and have also been affected by this vice when using a scribe to record observation data. Since one number looks so like another this error may not be picked up during an averaging or linear-fit exercise. However, if you graph those sights and compare them with the calculated (= true) slope, then such outliers immediately jump out and loudly exclaim: "Hey, look at me! Why do I stand out? Hey! What's going on here?"
