## 5 Short-Baseline Instantaneous RTK Performance with Smartphones in Lying Down and Upright Positions
### Instantaneous RTK Positioning Performance for Short-Baselines with External and Internal Antennas  
In Table 4, we summarize the ILS SRs and the empirical positioning mean and STDs (correctly fixed and float positioning errors) for the GP4 and S20 smartphones in the short-baseline experiments while using external (cf. Figure 3) and internal antennas (cf. Figure 4). The ILS SRs are shown for when the smartphones are both in an upright and lying down position, together with the mean number of tracked satellites over the 8 h and 3.5 h data periods for the external and internal antennas, respectively (cf. Table 2). Table 4 shows that the ILS SR decreases from 99.2% to 94.9% for S20 when the smartphones go from being in an upright position to lying down while using external antennas. We note that the reduction in ILS SR is a bit smaller for S20 for the short-baseline than in the zero-baseline case in Table 3. This is possibly caused by the shorter amount of data analysed (8 h vs. 12 h, cf. Table 2), as well as the fact that in the zero-baseline case there are more interferences possible since all four smartphones are then put into the _same_ RF shielding box (cf. Figure 2). We can also see that when internal antennas are used, we get a \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Baselines**} & **Antenna** & \multirow{2}{*}{**Setup**} & **ILS SR (\%)** & **Avg. \# of** & \multicolumn{2}{c}{**Mean \(\pm\) STDs (m)**} \\  & & & **(\%)** & **Sat.** & & **Correctly Fixed** & **Float** \\ \hline \multirow{8}{*}{\
\begin{tabular}{c} GPD1- \\ GPD2 \\ \end{tabular} } & \multirow{2}{*}{External} & upright & 99.9 & 24 & E & \(-0.001\pm 0.002\) & \(-0.105\pm 1.200\) \\  & & & & N & \(-0.000\pm 0.002\) & \(0.375\pm 1.294\) \\  & & & & U & \(-0.000\pm 0.005\) & \(-0.121\pm 2.567\) \\ \cline{2-7}  & \multirow{2}{*}{External} & lying & \multirow{2}{*}{99.9} & \multirow{2}{*}{20} & E & \(-0.001\pm 0.002\) & \(-0.016\pm 1.243\) \\  & & & down & & U & \(-0.002\pm 0.005\) & \(0.048\pm 2.644\) \\ \cline{2-7}  & \multirow{2}{*}{Internal} & \multirow{2}{*}{upright} & \multirow{2}{*}{98.7} & \multirow{2}{*}{21} & E & \(0.001\pm 0.005\) & \(-0.222\pm 2.977\) \\  & & & & & U & \(-0.001\pm 0.005\) & \(0.209\pm 3.483\) \\  & & & & & U & \(0.001\pm 0.010\) & \(0.370\pm 5.518\) \\ \cline{2-7}  & \multirow{2}{*}{External} & \multirow{2}{*}{lying} & \multirow{2}{*}{63.1} & \multirow{2}{*}{16} & E & \(-0.002\pm 0.008\) & \(-0.098\pm 2.909\) \\  & & & & & U & \(-0.000\pm 0.005\) & \(0.086\pm 2.516\) \\  & & & & & U & \(-0.002\pm 0.013\) & \(-0.907\pm 4.282\) \\ \hline \multirow{8}{*}{
\begin{tabular}{c} SGD1- \\ SGD2 \\ \end{tabular} } & \multirow{2}{*}{External} & \multirow{2}{*}{upright} & \multirow{2}{*}{99.2} & \multirow{2}{*}{15} & E & \(0.000\pm 0.003\) & \(-0.031\pm 0.729\) \\  & & & & U & \(-0.000\pm 0.006\) & \(0.091\pm 1.013\) \\ \cline{1-1} \cline{3-7}  & & & & U & \(-0.005\pm 0.009\) & \(-0.050\pm 1.730\) \\ \cline{1-1} \cline{3-7}  & \multirow{2}{*}{lying} & \multirow{2}{*}{94.9} & \multirow{2}{*}{20} & E & \(0.006\pm 0.006\) & \(-0.037\pm 0.070\) \\  & & & & & U & \(0.002\pm 0.007\) & \(0.043\pm 0.939\) \\ \cline{1-1} \cline{3-7}  & & & & U & \(0.001\pm 0.010\) & \(-0.124\pm 1.874\) \\ \cline{1-1} \cline{3-7}  & \multirow{2}{*}{Internal} & \multirow{2}{*}{upright} & \multirow{2}{*}{64.4} & \multirow{2}{*}{16} & E & \(0.001\pm 0.005\) & \(-0.222\pm 2.977\) \\  & & & & & U & \(-0.001\pm 0.006\) & \(0.210\pm 3.483\) \\  & & & & & U & \(-0.001\pm 0.010\) & \(0.274\pm 4.677\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Empirical ILS SRs, mean and STDs (East, North and Up) of correctly fixed and float positioning errors for instantaneous short-baseline dual-frequency RTK positioning, with 8 h and 3.5 h of data used for the external and internal antennas, respectively (cf. Table 2). Average number of satellites is denoted by Avg. # of Sat. poorer ILS SR for S20 of 64.4% when being in an upright position, and 27.5% when lying down.