## 5 Statistical Analysis  
In this chapter, the statistical analysis of a number of targets received from the sensors in the network and number of targets delivered to the C2 system is presented. In other words, this analysis shows the percentage of duplicate targets eliminated by the presented algorithm. Before analysis starts, a few things need to be pointed out:  
* The first HFSWR was commissioned in mid-January 2017, the second HFSWR in mid-September 2017. All Coastal sites are added to the network as they were commissioned, starting with 4 in mid-January and adding 2 more in mid-September. Due to this total number of targets will rise during the time. * Power supply issues are a common fact in Gulf of Guinea, not isolated incidents. Despite the fact that all sites are equipped with UPSs which can power the equipment for approximately 24 h, some sites are located in remote areas and cannot be reached within 24 h. This leads to the situations where a significant drop of the number of detected targets from one site are present, simply because the site was down. * A similar situation occurs when there is a major problem with the satellite links. The problem mostly occurs when storms are raging in a certain area and block satellite communications from sites located in that area. This also causes a significant drop of targets as long as the link is down. In Figure 10 one log file from our system is presented. Explanation of the log file fields:  
* Iteration--number of iteration process during single day
* Time--time and date when the log file was created  
Figure 10: One iteration log file. Figure 9: One MRFT and multiple AIS. * Update this cycle AIS MMSI--number of AIS massages received during this iteration process. Basically, number of AIS massages received in last 33 s
* Live AIS--number of MMSIs which received at least one update in last one hour
* FOTHR--number of active MRTFPs
* FOTHR single--number of MRTFPs which cannot be integrated with any live AIS
* Integrated targets--number of integrated targets
* AIS single--number of MMSIs which cannot be integrated with any live MRTFP
* Current number of total targets--number of targets delivered to C2 system  
Based on data displayed in Figure 10 the following can be concluded:  
1. Total number of targets received from all sensors is 20,
2. Total number of targets delivered to C2 system is 14,
3. Number of eliminated targets is 6. This means that 30% of all targets were duplicated and could cause false alarm triggers in C2 system. The log files were collected during the day in order to present the statistics for that day. The day log file is presented in Figure 11.  
So for one day, the HFSWR network detected 102 targets, while 48 targets were collected through AIS, meaning that in total, 150 targets were received from the sensor network during that day. 42 HFSWR targets couldn't be integrated with any AIS data and 12 AIS data did not have the corresponding HFSWR tracks, while for 60 HFSWR tracks 36 AIS data sources were found. Overall, 114 targets were delivered to the C2 system; 42 HWSWR, 12 AIS and 60 integrated. This means that 36 targets were eliminated during that day, or 24% of all received targets were duplicated. Please note, in this particular case there were more integrated HFSWR tracks than AIS data. Situations vary from day to day. Day log files are collected on monthly basis starting from the 1 February 2017 and ending with the 31 January 2018 in order to create a statistical analysis presented in Figure 12.  
Form Figure 12 it can be seen that around 650 duplicate targets were eliminated every month from February 2017 up to September 2017. A significant drop of targets can be noted during August, this is due to power issues with the HFSWR (at that time only one HFSWR in the network was functioning). During September, the second HFSWR was commissioned and 2 more coastal sites were added to the network, so the number of targets raised significantly. The drop which can be noted during December was due to the Holiday season.