geog2geomag <-> geomag2geog

[paulinchin]

It can be useful for geog2geomag.m/geomag2geog.m to adapt specification of the year for calculation of thetan and phin (now by default it is 1985 coefficients), something like:

% Schmidt semi-normalised spherical harmonic coefficients are from http://wdc.kugi.kyoto-u.ac.jp/igrf/coef/igrf13coeffs.html
% Calculation of thetan and phin are based on Millward et al., 1996
switch true

case ismember(year, 1920:1987)
thetan=deg2rad(1.1000e+01);
phin=deg2rad(2.8900e+02);
case ismember(year, 1988:1992)
thetan=deg2rad(1.0862e+01);
phin=deg2rad(2.8887e+02);
case ismember(year, 1993:1997)
thetan=deg2rad(1.0677e+01);
phin=deg2rad(2.8858e+02);
case ismember(year, 1998:2002)
thetan=deg2rad(1.0457e+01);
phin=deg2rad(2.8843e+02);
case ismember(year, 2003:2007)
thetan=deg2rad(1.0252e+01);
phin=deg2rad(2.8819e+02);
case ismember(year, 2008:2012)
thetan=deg2rad(9.9840e+00);
phin=deg2rad(2.8779e+02);
case ismember(year, 2013:2017)
thetan=deg2rad(9.6869e+00);
phin=deg2rad(2.8739e+02);
case ismember(year, 2018:2025)
thetan=deg2rad(9.4105e+00);
phin=deg2rad(2.8732e+02);
end

I'd suggest geog2geomag(lat,lon,year), but this will require change of all makegrid, gridplot, mag and TEC functions from ./mag-gemini and ./gemini-scripts. Let me know if you agree with these all changes, and if so I may change all routines calling geog2geomag/geomag2geog

[scivision]

This is fine, I think it will be more useful in general. I am used to making mass changes e.g. for loadframe() a few times

[scivision]

Let's discuss sometime. I think this is a worthwhile update if it fits our current priorities