STC-1.33 Erratum 1:

The formula in 4.5.1.4 states:

“A = - SUM[ A(i) ] – (n-2) *pi“

but:
A = (RA,DEC)[0] = (90, 0)

B = (RA,DEC)[1] = (0, 0)

C = (RA,DEC)[2] = (0, 90)

The three angles of the polygon are all 90 deg, or pi/2 rad by construction.

A in the above case is: -3 * pi/2 –pi = -5/2 pi

One expects an area of pi/2.

The correct formula is:

A = +SUM[ A(i) ] – (n-2) *pi