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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Z-correction using HO 229 & 249
From: Dave Weilacher
Date: 2004 Jan 24, 08:47 -0500
From: Dave Weilacher
Date: 2004 Jan 24, 08:47 -0500
First, my understanding. The Z-correction is used to correct the azimuth to the intercept you are going to plot. Is this correct?
Assuming it is:
Should this correction be made when using HO-249? If so, how do you go about determining it?
If this correction is ignored entirely, what are the limits of error that are being introduced to the plotted LOP? Said differently, if I don't make this correction, how far out of whack can I be?
In sight reduction, I always take two shortcuts to get a line of position. First, I use an AP that is derived by taking my DR longitude in whole degrees and the minutes and seconds from GHA. Can anyone see a trap in this that would produce unacceptable error? Second, I always skip the Z-correction. This also introduces an error.
My concern is that these two taken together can allow a plotted fix that has me in fantasy land.
Pragmatically, I'm still in the game when compared to answers for 'book' problems. I just don't have the mental horsepower to figure out how badly I can be off in real life.
Thanks
