Computes the Positive Gauss-Legendre quadrature
theta (Numeric) – The colatitude in radians
nmax (int) – The maximum degree of the polynomial matrix
Pnm (~pyarts3.arts.math.SchmidtMatrix) – The Polynominal matrix (nmax+1 x nmax+1).
dPnm (~pyarts3.arts.math.SchmidtMatrix) – The Polynominal matrix derivative (nmax+1 x nmax+1).