# Localization in Low Power Wide Area Networks Using Wi-Fi Fingerprints
## 2 Methods and Materials
### Wi-Fi Databases
* ```
*resultCount\":1,
*last\":1,
*success\":true,
*results[[\"trilat\":51.17709351,
*trilong\":4.41607475,
*ssid\":\"UAntwerpen\",
*qos\":1,
*transid\":\"20110605-00081\",
*firsttime\":\"2011-05-31T17:11:13.000Z\",
*lasttime\":\"2013-10-28T11:32:52.000Z\",
*lastupdt\":\"2013-10-28T09:33:29.000Z\",
*netid\":\"00:0b:86:26:86:16\",
*name\":null,
*type\":\"infra\",
*comment\":null,
*wep\":\"2\",
*channel\":6,
*bcninterval\":0,
*freenet\":\"?\",
*dhcp\":\"?\",
*paynet\":\"?\",
*userfound\":false}],
*first\":1
```

The documentation of both services helps to get started with making requests. However, the documentation of WiGLE is harder to find and understand, since it is still under development. The LocationAPI documentation is very easy to find, easier to read and it contains examples. Table 2 presents a summary of all the properties and characteristics of the two databases. \begin{table}
\begin{tabular}{l c c} \hline
**Property** & **WiGLE** & **LocationAPI** \\ \hline Amount of access points worldwide & 4,750,076,107 & 1,500,000,000 \\ Amount of access points in Belgium & 1,700,000 & 11,000,000 \\ Accuracy given in request & No & Yes \\ Balance given in request & No & Yes \\ Number of BSSIDs in a request & 1 BSSID & At least 2 BSSIDs \\ Number of coordinates in a response & 1 coordinate per WAP & 1 mean coordinate \\ Documentation & More complex & More intuitive \\ \hline \end{tabular}
\end{table} 
Table 2: Comparison of the properties and characteristics of the WiGLE and LocationAPI databases. Figure 1: WiGLE returns detailed information about an access point. Figure 2: LocationAPI returns only the average location of multiple BSSIDs, but also an estimated accuracy. ### Measurement Locations

Measurements are executed at 36 different locations in and around Antwerp. The locations are chosen so that there is a variety of more and less densely populated areas. At every location, a script is run to save all BSSIDs and RSSI values of the access points in the vicinity, together with the exact coordinate of the measurement location. Figure 3 shows a map of the different measurement locations. ## 3 Results

This section summarizes the location estimate results by database. First the WiGLE database, then the LocationAPI database, and finally the combination of both databases. For each database, we discuss the overall location error, the probability of finding the BSSIDs, and the location error when transmitting only the two BSSIDs with the highest received signal strength. ### WiGLE Results

The location estimates when localizing using the WiGLE database are prone to large errors, see Figure 4. The overall mean location error is 6.24 km, while the overall median location error is 77 m. The 75 th percentile location error is larger than 1 km only at locations 12 and 14; at location 14, it is 5.12 km. Ten locations have an error greater than 2 km, which are clipped in Figure 4. One of those

Figure 3: Measurement locations in Antwerp, ©2017 Google. See Figure S1 for an interactive version. is location 8. The mean location error is 101 km and the median location error is 45 m. To represent the measurement, a cumulative distribution of the errors at this location is shown in Figure 5. There are some combinations of BSSIDs with a significant location error: 802 km and 1633 km. However, more than 90% of the BSSID combinations have an error smaller than 119 m, see Figure 5b. The average probability of finding the BSSIDs in the WiGLE database of a single WAP at one of the 36 locations is 32.6%. This is calculated using Equation (1) with \(n=1\). The average probability of finding neither of two BSSIDs in the WiGLE database is 13.2%, which is calculated with \(n=2\) or:

\[P(\
eg 2B)=\frac{\binom{\
eg B}{2}}{\binom{W}{2}}. \tag{2}\]

A graph of the probability of finding neither BSSIDs in the WiGLE database is shown in Figure 6.

Figure 4: Overview of the location error on all 36 locations using the WiGLE database. Errors larger than 2 km are clipped.