Response to Reviewer 3
- Is the manuscript technically sound, and do the data support the conclusions?
The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.
Reviewer #3 (closed): Partly
- Has the statistical analysis been performed appropriately and rigorously?
Reviewer #3 (closed): No
- Have the authors made all data underlying the findings in their manuscript fully available?
The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.
Reviewer #3 (closed): Yes
- Is the manuscript presented in an intelligible fashion and written in standard English?
PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.
Reviewer #3 (closed): No
- Review Comments to the Author
Reviewer #3 (closed): Summary: This paper presents a technique to measure boat-speed and distance traveled for competitive rowing application. Measurements of position and velocity are obtained using smart-phone based GPS and accelerometer sensors. The estimates for boat-speed and distance traveled are proposed to be calculated in real-time using digital filters which combine acceleration and location data using (a) a frequency-response filter and (b) a Kalman filter. A separate Differential-GPS system is used as a reference for comparison purposes.
The authors presented a simple technique that offers incremental improvement over estimates available directly from smartphones. There are several issues in the description of the technique as well as writing of the manuscript in terms of the language and presentation. I suggest the authors to perform major improvements to their work. Below are some specific comments.
Section: Related work, paragraphs 2 and 3: Authors should discuss the drawbacks of the techniques mentioned here along with how their own work can help overcome those drawbacks.
Line 108: What does "Physics-informed fusion" mean?
You are proposing solution for a problem where accuracy and precision are critical. In this case, why wouldn't it be recommended to just use the differential gps?
Define the symbols/variables in equation (4), the interpretation is left to the reader.
Use subscript at all points in the manuscript to clarify whether a parameter (example d(ti)) is related to smartphone or gps, etc.
You are using the symbol 'n' both for averaging over number of samples in Eq. (6) and (7) and also when averaging over time points in Eq. (8)-(10). This is not the correct way to present formulations. Separate symbols should be used and consistencies should be maintained to avoid any confusion.
The paper's title include "Adaptive Smartphone based..". However, the authors report that the primary algorithms are designed for real-time purposes but evaluated offline for the purpose of the paper. It is important to show how efficient the algorithms are computationally when implemented on a smartphone as that is the true purpose and a major claim of the paper to provide estimates in real-time. Otherwise, the comparison with other techniques cannot be fair. I suggest including information on how fast the estimates are computed. When you say "smartphone based", there needs to be evaluation that is smartphone based.
Page 8, paragraph 1, (line numbers missing): "As described in the text" refers to where exactly?
Page 8, paragraph 2, (line numbers missing): "If the smartphone pitch, θ, and the vertical acceleration of the boat are small, then the longitudinal acceleration a is given by:" Please provide reference or further explanation.
Sensor Fusion Method 1: Complementary Filter - This section provides very basic level of filter design information taught at an undergraduate level. What needs to be presented in this paper is how this choice of filter suits this application. This can be shown, for example, by presenting an analysis through plots of how accelerometer bias and noise comprise of high/low frequency components.
Explain the formulation on lines 276-277 in more detail.
Eq (27)-(28): You been using x,y as coordinates so better not use them as symbols for state vectors for Kalman filter. Use some other symbols.
Lines 364-368: If the Kalman converges slowly, how effective can it be in a race?
There is too much content describing very basic components. A research publication should focus on detailing the novelty and applicability of the tools to a particular problem. This needs to be done by presenting thorough analysis of the signals under consideration and significance of results. The Results section in this manuscript present very minimum findings and discussion compared to the overall length of the paper. I suggest the authors to include more results and detailed analysis and discussion.
Further examples for improving the manuscript text:
Line 83: Do not reference to an author as 'His'. An appropriate way is "The technique in [reference].."
Line 91: "using readily available and easy to use consumer products, i.e., smartphones" should be changed to "using a readily available and easy to use consumer product, such as, a smartphone"
Line 101: "accomplish this' should be changed to "accomplish these"
Line 133: RSME = RMSE
I recommend having the paper proof-read by someone more experienced in writing a research publication. The current quality of the manuscript text resembles more to a casual technical report.