$h_{{\Phi }_{IF}}$	ionosphere-free combination (m)
${\rho }_i^k$	modelled geometric range (m)
c	speed of light in vacuum (m/s)
${\delta }_i$	receiver clock offset (s)
$A_i^k$	non-integer ambiguity term (m)
${\theta }_i^k,{\psi }_i^k$	elevation and azimuth angles (rad)
$T_{zwd}$	zenith wet troposphere delay (m)
$m_G\left(\right)$	Global Mapping Function (GMF)
$G_N,G_E$	north and east troposphere gradients