Public Member Functions | |
| subroutine | bestesg_map (lam, marcx, marcy, a, k, garcx, garcy, q, ff) |
| Get the best Extended Schmidt Gnomonic parameter, (a,k), for the given map-coordinate half-spans, marcx and marcy, as well as the corresponding geographical half-spans, garcx and garcy (in degrees) and the quality diagnostic, Q(lam) for this optimal parameter choice. | |
| subroutine pesg::bestesg_map::bestesg_map | ( | real(dp), intent(in) | lam, |
| real(dp), intent(in) | marcx, | ||
| real(dp), intent(in) | marcy, | ||
| real(dp), intent(out) | a, | ||
| real(dp), intent(out) | k, | ||
| real(dp), intent(out) | garcx, | ||
| real(dp), intent(out) | garcy, | ||
| real(dp), intent(out) | q, | ||
| logical, intent(out) | ff ) |
Get the best Extended Schmidt Gnomonic parameter, (a,k), for the given map-coordinate half-spans, marcx and marcy, as well as the corresponding geographical half-spans, garcx and garcy (in degrees) and the quality diagnostic, Q(lam) for this optimal parameter choice.
If this process fails for any reason, the failure is alerted by a raised flag, FF, and the other output arguments must then be taken to be meaningless.
The diagnostic Q measures the variance over the domain of a local measure of grid distortion. A logarithmic measure of local grid deformation is give by L=log(J^t.J)/2, where J is the mapping Jacobian matrix, dX/dx, where X is the cartesian unit 3-vector representation of the image of the mapping of the map-coordinate 2-vector, x. The Frobenius squared-norm, Trace(L*L), of L is the basis for the simplest (lam=0) definition of the variance of L, but (Trace(L))**2 is another. Here, we weight both contributions, by lam and (1-lam) respectively, with 0 <= lam <1, to compute the variance Q(lam,a,k), and search for the (a,k) that minimizes this Q.
The domain averages are computed by double Gauss-Legendre quadrature (i.e., in both the x and y directions), but restricted to a mere quadrant of the domain (since bilateral symmetry pertains across both domain medians, yielding a domain mean L that is strictly diagonal.
| [in] | lam | |
| [in] | marcx | map-coordinate half-spans |
| [in] | marcy | map-coordinate half-spans |
| [out] | a | Extended Schmidt Gnomonic parameter |
| [out] | k | Extended Schmidt Gnomonic parameter |
| [out] | garcx | geographical half-spans |
| [out] | garcy | geographical half-spans |
| [out] | q | |
| [out] | ff | failure flag |
Definition at line 1072 of file pesg.f90.
References pietc::ms18, pietc::ms36, pietc::ms54, pietc::ms72, pietc::o5, pietc::pi2, pietc::s18, pietc::s36, pietc::s54, pietc::s72, pietc::u0, pietc::u1, pietc::u2, and pietc::u5.
1.11.0