Comparison of the ERM borehole instrument with the inverted GeoTom data is shown in Figure 22.2. The correlations for each single test site were 0.559 at Bornim, 0.709 at Golzow, and 0.896 at Kassow. No measurements with the ERM were made at Beckum. The t correlation over all fields was 0.703 (Pearson's r is 0.871 for log-l°g transformed values). This comparison FIGURE 22.2 Log-log scatterplot of inverted sur-confirms the reliability of the GeoTom surface face measurements by the GeoTom versus borehole readings. readings by the Earth Resistivity Meter (ERM).
Correlation results for ARP03, Veris 3100, EM38 (EM38-DD), and CM-138 are presented in Table 22.1. EM38-DD and EM38-MK2 were only tested at Bornim. The results for the EM38-DD are presented in Table 22.1; they are similar to correlations obtained with an EM38 in two runs using the horizontal and the vertical mode. The horizontal mode output of the EM38-MK2 can be related best to GeoTom level 2 (t = 0.606), the vertical mode output can be related to GeoTom 3 with t = 0.666. Repeated runs yielded a correlation of 0.721 (horizontal) and 0.797 (vertical).
Repeated runs with the ARP in Golzow achieved a t of 0.839, 0.874, and 0.864 for the first, second, and third levels. Repeated runs with the CM-138 at Golzow produced a t of 0.794 in the best case and 0.598 in the worst case. Two runs with Veris in Bornim correlate with a t of 0.854 (level 1) and 0.843 (level 2).
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