A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Robin Stuart
Date: 2015 Mar 7, 12:34 -0800
At Antoine/Kermit’s request I have repeated the calculation of g30535 on set #2 of sights he gives in his post g30478. The results are more or less as anticipated. For Kermit’s sights the 3 parameter fit produces an estimate position (EP) that is over 20nm from the actual one and hence the I.E. needs to be correspondingly large before the 3 parameter fit, MPP3, beats MPP2.
It should be noted that the azimuth’s in this set of sights all fall within a narrow range of only 45°. This is far from ideal and means that the EP is very sensitive to small changes in the intercepts. This is a significant factor in why the 3 parameter fit performs poorly in this case. For reference I have plotted the sights and some contours of the probability density function,