The code pseudorange at an epoch t can be modeled, cf. Eq. (6.2), by $$R_{i}^{j}(t) = \varrho _{i}^{j}(t) + c\Delta \delta _{i}^{j}(t).$$ (8.1) Here, R i j (t) is the measured code pseudorange between the observing site i and the satellite j, ϱ i j is the geometric distance between the satellite and the observing point, and c is the speed of light. The last item to be explained is Δδ i j (t). This clock bias represents the combined clock offsets of the receiver and the satellite clock with respect to GPS time, cf. Eq. (6.1).