# Comparing Monitoring Networks to Assess Urban Heat Islands in Smart Cities
## 5 Analysis of the Measurement Data
### Control Points  
Eight control points are identified (CP1 to CP8) (Appendices B and C), distributed throughout the city, that are used to compare all the networks: on five occasions AWSs of Bs and WU (CP3 to CP7), on one occasion AWSs of Bs and Nt (CP2) and AWSs of Nt and WU (CP8) and, at one of the control points (CP1), three AWSs, one corresponding to each network. This study uses scatter plots to check the intensity of the existing relation between the data pairs from the AWSs via linear and quality adjustments of the regression obtained from the determination coefficient R\({}^{2}\) (in general, the closer the R\({}^{2}\) value is to 1, the stronger the connection between the two variables, allowing the regression model to be trusted with a high level of confidence). Looking at the results obtained (Figure 9), there is an evident linear relation in general terms between the data pairs. However, it is worth noting that R\({}^{2}\) between Bs and Nt, in CP1 and CP2 (0.95458 and 0.91868), is notably lower than those obtained in four of the Bs and WU, in CP3 to CP6 (0.98038 \(\pm\) 0.00857). It should be pointed out that the behavior of Bs and WU in CP7 (0.93031) is different. When visiting the area, it is possible to see that there is in fact, no AWS in that location. Between Nt and WU in CP8, there is a high R\({}^{2}\) (0.97411), and in this case, the distance between the sensors is less than 20 m.  
In CP1, a lower consistency in the data from the AWS of Nt can be appreciated. The pairs between Nt and Bs (R\({}^{2}\) = 0.95458) and Nt and WU (R\({}^{2}\) = 0.94581) present a similar scattering with respect to the cloud of general points. Nevertheless, when the projection of the Bs and WU pairs of data are analyzed, the correlation is greater (R\({}^{2}\) = 0.98202) (Figure 10). Figure 9: Scatter plot and linear fit of the Control Points, from 1 to 26 August 2024. Typical Week  
In general, the weekly analysis (Figure 11) shows that the data from the AWSs of Bs and the WU fluctuate in a similar way (practically identical from CP3 to CP6), with hourly mean differences of 0.8 \(\pm\) 0.8 \({}^{\circ}\)C (less than 1 \({}^{\circ}\)C in 70% of the registers) considering the total number of control points of the two networks. However, the values of the AWSs of Nt present an hourly mean difference of 1.8 \(\pm\) 1.0 \({}^{\circ}\)C and 1.7 \(\pm\) 1.4 \({}^{\circ}\)C, respectively, with respect to the AWSs of Bs and WU (less than 1 \({}^{\circ}\)C in 27% and 40% and in 38% and 33% greater than 2 \({}^{\circ}\)C of the registers, respectively). This difference between the AWSs of Nt and the rest are greater than 12 h and 15 h, even surpassing 6 \({}^{\circ}\)C of difference. The following general conclusions have been obtained from the analysis of the indicators for each of the CP (Table 1):  
* Similar amplitude with small deviations with respect to the mean, from 0 \({}^{\circ}\)C to \(\pm\)1.0 \({}^{\circ}\)C.
* Higher daily registers in the Nt AWSs with respect to the rest, with a mean of 1.6 \(\pm\) 0.4 \({}^{\circ}\)C in the minimum and 2.5 \(\pm\) 0.4 \({}^{\circ}\)C in the maximum with respect to the Bs AWSs, and 1.0 \(\pm\) 0.2 \({}^{\circ}\)C and 2.4 \(\pm\) 0.3.1 \({}^{\circ}\)C, respectively, with respect to the WU AWSs. The differences between the values of the WU and Bs AWSs are small (0.6 \(\pm\) 0.4 \({}^{\circ}\)C in the minimums and 1.1 \(\pm\) 0.8 \({}^{\circ}\)C in the maximums). * Weekly average greater in the Nt AWSs, with a mean of 1.4 \(\pm\) 0.1 \({}^{\circ}\)C and 1.4 \(\pm\) 1 \({}^{\circ}\)C with respect to the Bs and WU AWSs. There is a mean difference of 0.4 \(\pm\) 0.3 \({}^{\circ}\)C in the weekly average of Bs and WU AWSs. * A greater average of CDD in the Nt AWSs, with respect to the rest, in totals: 15% and 14% more with respect to the Bs and WU AWS; during daylight: 10% and 9%, respectively; and during the night: 27% and 23%, respectively. Figure 10: Scatter plot of CP1 comparing Bs, Nt, and WU AWSs, from 1 to 26 August 2024.