The spreadsheet alt_prec.xls is a reversed version of alt_corr.xls. It provides the altitude Hs to which the sextant may be preset before an observation. The observed altitude Ho (computed with intercept.xls) is now input in cell B12 and the sextant altitude is displayed in cells B1 and C1. The remaining cells have the same meaning as in alt_corr.xls.

Summary for spreadsheet alt_prec.xls:

Input cells: B2, B4, B11, B12, E1, F1, E2, E3, (E6, E8, E9 optional)

Output cells: B1, C1, B6, B7, B8

Input/Output cells: E11, E12