Table 1 Constraints on atmospheric delays and their estimable forms in the code-plus-phase ionosphere-float, ionosphere-weighted, and ionosphere-fixed models
From: PPP–RTK functional models formulated with undifferenced and uncombined GNSS observations
Model | Parameter | Constraint | Estimable form |
|---|---|---|---|
Ionosphere-float | Troposphere | None | \(\tau_{r}\) |
Ionosphere | None | \(\overline{l}_{r}^{s} = l_{r}^{s} - d_{{,{\rm GF}}}^{s} + d_{{r,{\rm GF}}}\) | |
Ionosphere-weighted | Troposphere | \(m_{1}^{s} = \cdots = m_{n}^{s}\) | \(\tilde{\tau }_{r} = \tau_{r} - \tau_{1} \,\) |
Ionosphere | \(0 = l_{r}^{s} - l_{1}^{s}\) | \(\tilde{l}_{r}^{s} = l_{r}^{s} - d_{{,{\rm GF}}}^{s} + d_{{1,{\rm GF}}}\) | |
Ionosphere-fixed | Troposphere | \(m_{1}^{s} \tau_{1} = \cdots = m_{n}^{s} \tau_{n} = \tau^{s}\) | None |
Ionosphere | \(l_{1}^{s} = \cdots = l_{n}^{s} = l^{s}\) | \(\overline{\overline{l}}^{s} = l^{s} - d_{{,{\rm GF}}}^{s} + d_{{1,{\rm GF}}}\) |