8.4.2 Ionospheric Function and Cycle Slips
Dual-frequency observations can eliminate the first-order ionospheric effects by forming the popular dual-frequency ionospheric-free functions. Consider the relevant terms of the ionospheric-free function (6.1.41)
and the ionospheric function (6.1.44)
with , , and the squared ratio as already defined in (6.1.1). Analyzing these dual-frequency carrier phase functions requires extra attention because certain cycle slip combinations on L1 and L2 generate almost identical effects. For example, consider the ionosphere-free phase observable (8.4.24). The ambiguities enter this function not as integers but in the combination of , causing noninteger change when cycle slips occur.
Table 8.4.1 lists in columns 1 and 2 small changes in the ambiguities and shows in columns 3 and 4 their effects on the ionospheric-free and the ionospheric phase ...