|I appreciate the additional effort the authors have invested into this revised manuscript. After reading, I have prepared and compiled further comments.|
While the authors have improved the manuscript in several key areas (namely in the Introduction and Materials sections), the biggest concern that I had with the previous version – which is still evident in the current version – is the lack of an apparent scientific novelty, even though I appreciate the technical novelty in the terms of a GSM module. It still feels that the authors rely heavily on the Materials section, which is in all fairness quite interesting to me. However, an original research article should present a lot more information in the Results and Discussion sections, where the research hypothesis is sufficiently challenged. As for the Materials section, perhaps too much space is given to the small technicalities such as the instructions on how to use the associated webpages which is a trivial information.
From my understanding, the main question raised in the abstract appears to be “can [this] be done cheaply and simply enough while using a GSM module?” Even while it is stated in the authors response that the geoscience research area is lacking a technical note paper category (with a broad reach), a candidate research article should still provide a sufficient amount of scientific novelty. In the current form, the manuscript is a good candidate for a technical note, but the prevalence of qualitative over quantitative information prevents it from achieving higher status.
However, the more I read through the manuscript, the more I appreciate certain aspects of it. My opinion is that if the Results and Discussion could be expanded to include additional data, as well as provide more quantitative information over qualitative, the manuscript would be significantly more valuable and could be accepted as an original research article. I will try to provide some ideas within some specific comments.
1. My intention was definitely not to invalidate (or even lessen) the title of a “tinkering scientist” (I would consider myself a part of this group as well), but to indicate that such title is quite vague. One could very easily argue that every scientist could be thought as a “tinkerer” with regards to hardware, software, mathematical models, numerical models, etc. For that reason, the term feels rather redundant and “colloquial”. However, the editorial team might disagree with me in which case my comment could be disregarded as this is not a critical issue.
2. In the answer to the reviewer #1 comments, a discussion is continued regarding the skills of the geoscientist. With the abundance of both official and non-official documentation on the low-power electronics, I would agree with the reviewer #1 that a team of scientists should have sufficient (at least collective) skillset to assemble a low-power Arduino(-based) platform, especially considering the fact that most scientific teams are heterogenous in terms of qualifications and skills.
3. I appreciate the discussion on the possible use of EEPROM instead of SD storage. One should be aware that Particle Electron does not actually have EEPROM, but rather uses 2kB of flash memory as emulated EEPROM across a larger portion of flash memory in order to reduce page wear. This argument could support the use of external memory, even though the OpenLog increases the overall power consumption. However, I do not agree that the EEPROM approach adds significant complexity for the data retrieval – storing to EEPROM is trivial, and reading is as simple as triggering the serial port to print the EEPROM storage to terminal, or even just printing EEPROM on board reset. I find that the main limitation of EEPROM is its limited size and flash page wear.
4. Even though a more detailed analysis of the total power consumption during deep sleep and operation would be interesting, I understand the complexity of such measurements and therefore appreciate the reference to previous studies on this topic which in this case should be sufficient.
5. In section 2.4 it was stated that the “… drifter followed the flow of the river.” However, this was not proven of verified in this research, or at least not presented in this manuscript. This section could be rephrased to explain that it was observed (I assume) that the drifters generally followed the observable surface flow trajectories, that the drifter velocities are likely (to a certain degree) impacted by its size and weight, but that the analysis of this impact was not performed at the current stage of the research.
6. In order to improve the Results and Discussion and increase scientific significance, I strongly advocate for improvements to the Results and Discussion sections, for example with the introduction of additional data: number of failed experiments/percentage of missing data and the explanation of corresponding issues, distances traveled by drifters, registered GPS and GSM signal strengths across the drifter track, average drifter velocities, postprocessing procedures applied to each dataset, and other available data. Since the authors have likely provided only the best available datasets, additional data could help readers to obtain a better insight into the overall robustness of the method. Would it also be possible to present the model results by Bakker (2017) along with the drifter field data with an appropriate comparison and discussion? This could be a very useful improvement to the Results section at the moment since no additional measurements were conducted in parallel.
I find that almost all of the technical comments have been addressed. Remaining issues I have noticed:
1. The term “fished-out” (previously lines 147-8, now 174) is still present in the manuscript, but is marked as changed in the authors answer to the previous revision.
2. Some minor spelling/grammar errors persist and will likely be addressed by the technical editor/team.