Fig. 3
From: Hydrological gravity response detection using a gPhone below- and aboveground
Groundwater levels (Wu, unconfined SBS16; Wc, W′c, confined TGR350), the free-air (FA) gradient effect, residual gravity (first- and second-order curve fittings), and predicted gravity levels calculated from the two groundwater levels are shown. W′c (bold dashed line) represents the Wc curve smoothed (thin solid line) using a weighted least-squares method (Chambers et al., 1983) to reduce diurnal-semidiurnal tidal variations.