Polar Motion
CALL sla_POLMO (ELONGM, PHIM, XP, YP, ELONG, PHI, DAZ)
ELONGM  D  mean longitude of the site (radians, east +ve) 
 
PHIM  D  mean geodetic latitude of the site (radians) 
 
XP  D  polar motion $x$coordinate (radians) 


YP  D  polar motion $y$coordinate (radians) 
ELONG  D  true longitude of the site (radians, east +ve) 
 
PHI  D  true geodetic latitude of the site (radians) 
 
DAZ  D  azimuth correction (terrestrial$$celestial, radians) 
ELONG  =  ELONGM+XP*COS(ELONGM)YP*SIN(ELONGM) 
PHI  =  PHIM+(XP*SIN(ELONGM)+YP*COS(ELONGM))*TAN(PHIM) 
DAZ  =  SQRT(XP*XP+YP*YP)*COS(ELONGMATAN2(XP,YP))/COS(PHIM) 
X  =  COS(ELONGM)*COS(PHIM) 
Y  =  SIN(ELONGM)*COS(PHIM) 
DAZ  =  ATAN2(X*YPY*XP,X*X+Y*Y) 