Sorry, 30 years since college and I wasn't awake all the time. I'm trying to translate the symbology in the attached pics. Some of the super/subscripts are throwing me off in formulae 13, 14 and 15. Y and X = planar coordinates of points. n = number of points. σβ = standard error of angle observation. σs = standard error of distance observation. Σ = the sum in parenthesis. Si = sum of distances. The parenthesis are the problems. Would Xn equal the last coordinate and Xi-1 each proceeding coordinate, so that I should sum the final minus each proceeding X? The same formulae in 3-91.