## 3 Experiment and Analyses
### Analyses of Static Experiments
#### 3.1.3 Results of AFM and the Exploration of Efficiency and Reliability  
Based on the convergence value of DPL, the search grid of AFM is established. The coordinates of the highest AFV (the precision depends on the search step length) can meet the initial value requirement of the LAMBDA method. Since the sub-meter precision can be obtained by static DPL, the search space of AFM can be adopted at about 1 m. This will play an important role in the study of efficiency and the multiple peaks problem in the following processing. The Effect of AFM Step Length and Scope on Multi-Peaks and Efficiency  
Step length is one of the factors that affect the efficiency and reliability of AFM. The core idea of this method is to obtain an initial coordinate that meets the requirement of LAMBDA through AFM, so the step length to be taken does not need to be too small (the centimeter level is enough). Search efficiency does not depend on the experimental data itself. In this paper, the short baseline static experiment is taken as an example to explore the search efficiency under different conditions. The statistical results are as follows:  
In Table 1, it is known that if the search range is larger and the search step length is smaller, the efficiency will be greatly reduced. Therefore, the search scope should be reduced and the step length should be increased properly, so that the initial coordinates to meet the accuracy requirement of LAMBDA method can be obtained in a very short time. Since the decimeter level precision coordinates can be obtained through the DPL method, the range can be 1 m. The step length can be 2 cm or 4 cm to ensure the precision of the coordinates correspond to the highest AFV. The first step of the algorithm is static initialization. The initial coordinates of positioning are obtained through DPL + AFM and the LAMBDA method is still used in the following steps to obtain the correct ambiguity resolution (AR). Thus, the search time is calculated in the initialization stage (DPL + AFM) rather than in the positioning stage. Figure 7 reveals the AFVs (ambiguity function values) whose search space is established based on the DPL convergence value in the zero and short baseline static experiments under different step lengths. The left side is the zero baseline static experiment. The step length is 1 cm, 2 cm, 4 cm, and the search space is 1 m. The right shows the short baseline static experiment. The step length is 1 cm, 2 cm, 4 cm, and the search space is 1 m, too. It is intuitively shown that the AFVs near the peaks can be diluted when the step length is slightly larger. At the same time, the efficiency can be also improved, so as to achieve rapid initialization. Additionally, the precision of the coordinates is determined by the step length, but the step length should not be too large, otherwise it may hide the real peak. The wrong peak in the experiment will be explained in the next chapter. The search scope is another factor affecting the efficiency of AFM, and it also affects the reliability of AFM [31; 32]. The search scope in this paper is based on the convergence precision of DPL. Under the \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Search Scope/m**} & \multicolumn{5}{c}{**Search Step/cm**} \\ \cline{2-6}  & **0.1** & **0.5** & **1** & **2** & **4** \\ \hline
0.5 & 5.032 & 0.203 & 0.051 & 0.012 & 0.004 \\
1 & 20.495 & 0.823 & 0.207 & 0.051 & 0.012 \\
2 & 83.901 & 3.299 & 0.834 & 0.205 & 0.053 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Search time under different conditions/seconds. condition of ensuring a reasonable scope, a proper reduction in the search range can also be a good way to remove the wrong peaks. (2) AFM Multi-Peaks and The Coordinate Precision Corresponding to the Highest AFV  
If the parameters of AFM are not reasonable, it is difficult to avoid the emergence of the multi-peaks problem. We search in different epochs, respectively, to remove some wrong peaks, and the real peak should be consistent theoretically in different epochs.