## 2 Materials and Methods  
### Measurement Equipment and Procedure  
The set of measurements corresponds to those carried out in 38 different locations for 6 min on average, covering the urban area of Tarancon (Spain) in February 2018. A Narda BBM model EMR-300 with an 18C isotropic probe was used to carry out the measurements; it was placed at a height of 1.5 m on a non-metallic tripod EMCO 11689C. The PEM model used was the Satimo EME Spy 140. The ranges of the BBM Narda (from 100 kHz to 3 GHz) and the PEM Satimo EME Spy 140 (from 88 MHz to 5.8 GHz) do not match exactly. For this reason, the exposure meter bands above 3 GHz were discarded, and it was assumed that the contributions in the area below the FM Broadcasting Service (less than 88 MHz) can be considered negligible. During the fieldwork, and to the authors' knowledge, no local emitters were found in the range between 100 kHz and 88 MHz that could contradict this assumption.  
Static measurements were taken at specific points to compare the performance of the BBM and the PEM; the variability between BBMs and smartphones and the use of continuously moving PEMs in a closed environment were analyzed previously [9; 10; 11]. In this case, we used two PEM, placed on either side of the hip of the volunteer, configured to measure every 5 s. The electric field value corresponding to that location was determined from the average of the values taken during the 6 min of the measurement interval. During the 6 min measurement, the volunteer carrying the PEMs was continuously moving around the static probe placed on a tripod. There is a slight difference in height between the BBM (1.5 m) and the PEMs located at the hips (approximately 1 m). No correction for this difference is proposed in this study, as we implicitly assume that movement around the BBM can correct for the small differences in the values at the two positions. The broadband isotropic probe provides a single value of electric field, which integrates the total power measured over all bands and from every possible location, averaging the values taken across the 6 min measurement period. PEMs are usually used by travelling along the area to be measured, taking measurements at the chosen periodicity, without carrying out six-minute averages [12]. In this case, to obtain the possible equivalence for the purposes of environmental compliance and to eliminate the influence of the volunteer, a circular path around the measurement point in a range of about 3 m was proposed. The goal was to be able to produce equivalent exposure maps using BBM from a fixed point and PEM moving over a small area around that point for a measurement period of six minutes in both cases.  
Note that these measurements were made prior to the revision of the ICNIRP 2020 recommendations [13] and therefore follow the previous 1998 guidelines [14]. The levels may have changed today, but the aim of this study is not to produce a map representing the current values, a task that can be undertaken in future, but to assess the possibility of making such an exposure map with a PEM instead of a BBM. The measurement points were selected following a criterion of homogeneous distribution in the urban area of the municipality. The area covered is 5.13 km\({}^{2}\) and the perimeter of the area is 10.2 km. There were 38 measurement points, so the density of points is 7.40 points/km\({}^{2}\), similar to the value discussed in other works [15] and considering typical distances between points of 0.3 Km, although some of those located in the southern area may double this value. The sites were located in open areas. For each site, the existence of direct line of sight (LOS) or not (NLOS) with any of the mobile telephony base stations (BTS) existing in the municipality was noted. In this way, the dataset is divided into 18 sites with direct line of sight to the antenna and 20 without it. The measurement points in each case and the position of the BTS are shown in Figure 1.