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DaveP,

     You can change any of the values in the yellow shaded cells of the spreadsheet and have it recalculate (Be sure to click "Enable Content").

The warm ‘fuzzy’ feeling you get from a tiny cocked hat is justified in that it means that the HMNAO methods would produce correspondingly small value for the estimated position error, σ (although with just 3 sight there will a fair degree of uncertainty in the estimate). In fact it is possible to show that for 3 sights, both the square root of the area of the cocked hat and the estimated position error are proportional to the quantity B in cell R12 of the spreadsheet.

I included the calculation of the probability that the cocked hat encloses the true position, in the column labelled "Enclosure Probability", mainly to emphasize that for any particular realization of a cocked hat, it is in general NOT 25%. Cell R17 is the only place where the macros needed and if you disable them, everything else should still work.

Regards,
Robin