Help translating subscripts in surveying formulas 13, 14, 15

[Scott S]

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.

 

[Ray Vickson]

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?
View attachment 96281

The same formulae in 3-91.
View attachment 96282

For example:
$$\begin{array}{l}\sum_{i=1}^n \left( \frac{X_i - X_{i-1}}{S_i} \right)^2\\<br /> = \left(\frac{X_1-X_0}{S_1}\right)^2 + \left(\frac{X_2 - X_1}{S_2}\right)^2 + \cdots + \left( \frac{X_n - X_{n-1}}{S_n}\right)^2<br /> \end{array}$$
Is that what you were uncertain about?

 

[Scott S]

Yes!
Thank you.