Monitoring of Land Subsidence in the Po River Delta (Northern Italy) Using Geodetic Networks
Round 1
Reviewer 1 Report
The authors present the monitoring of the subsidence of the Po River delta in Italy using GNSS permanent and repeated networks and radar interferometry. I would encourage the authors to improve the bibliography, and in particular read and cite a recent paper by Vitagliano et al. (2020) (doi:10.3390/rs12091465).
Overall the manuscript is clear and well written and deserves to be published after some minor revisions.
- page 5, line 210: IGS is the International GNSS Service
- page 5 lines 218-226: I do not understand the discussion regarding the difficulties to estimate positions and velocities in the ITRF; they could add other stations, even a little further away from the studied area. This has been classically done for decades now.
- Page 6, line 249 (Equation 1): it may be dangerous to find 5 different sinusoidal signal to represent the seasonal variations. Usually, an annual & a semi-annual signals are adjusted. Their justification of this choice relies on 3 citations [21], [34] and [62], which are self-citations.
I am wondering what are the correlations between the periodic terms and the linear trends.
- Page 7, lines 286-287: Again, they refer to self-citation for the choice of the VMWA method. I would like to see a comparison with a more classical velocity estimate.
- Page 9, table 2: the values of the linear trends using the VMWA and the campaign methods are quite different, even sometimes in opposite directions. It should be discuss way further; it raises the question of the validity of their methods to compute velocities.
- Page 13, lines 418-421 and Figure 6. The authors did not justify the choice of the 30-meter averaging radius. There is no need to show the plot up to 300 meter radii. However, it might be interested to do more test with smaller sampling than 10 meter.
- Page 14, Table 4: The differences between INSAR & GPS is equal to 0 for CODI station, as it is used for the adjustment. However, the differences are pretty significant for PTO1 and TPGO, on the order of 10% of the signal. Is it significant, or is-it within the estimate errors ?
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Reviewer 2 Report
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Round 2
Reviewer 2 Report
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