The paper by Matsushita et al, “The azimuth observation by GNSS: A case study at Kakioka” is an interesting read. The text is generally easy to follow, and the language is clear. I do not have a background in magnetic observatories, so I can not adequately comment on the novelty of the research. My recommendation is publication following a minor revision.

In the title, I suggest that the authors spell out GNSS, so it is immediately clear to all readers, including those outside the magnetic observatory community, what this paper is about by reading the title.

The introduction is a bit short, and the manuscript contains a very limited number of references. As such, this is not an issue, but I suggest that the author consider expanding the introduction with one or two more paragraphs with background, e.g., the issues that led to this research must likely also be issues at other laboratories.

It’s a minor issue, but the schematic diagram in figure 1 is not really matched to the actual layout in figure 1. Could the schematic diagram be “twisted” a bit to make the resemblance more intuitive?

Figure 4 contains some clear outliers where the signal systematically jumps several arcseconds back and forth. It would be appropriate to include a discussion of the origin of these outliers and how they are handled, e.g., personally, I would be tempted to cull outliers.

The authors find a systematic difference between Polaris observations and GNSS observations. It is suggested that Deflection of the Vertical (DoV) is the main reason for this, and convincing arguments are made. However, it would be appropriate to include a short discussion of any other potential sources for a systematic difference.

In the summary of the manuscript, it is not really clear, but still implicitly suggested that JMA is moving towards GNSS based azimuth observations. It would be interesting for the readers to learn a bit more here. Has a decision been made and if so, how will the systematic difference be handled?

The paper by Matsushita et al, “The azimuth observation by GNSS: A case study at Kakioka” describes how to perform GNSS measurements for geomagnetic observatory work.

Please see my comments below:

The paper is well written and the methods as well as the procedures are presented in a concise way. After reading the whole paper, I was wondering about the scientific significance of the approach. Even this might be a relative new way for some geomagnetic observatories, GNSS observations is a common practice in surveying and a well established method. To improve the paper I would suggest following:

• The introduction should cover more the pro and cons of different GNSS survey modes with respect geomagnetic observatory work.
• The allover critical value is β_GSNN. There should be a serious discussion how this angle is derived out of the GPS measurements. How does the distance between between the points influence the accuracy? How does the calculation is affected with errors?
• As the angles β₁ and β₂  are measured with a theodolite are they also affected by DoV? When yes, how does this influence affect the overall angle θ₂ ?
• In the comparison between Polaris observations and GNSS observations, there should be a summary on the Polaris observation method and how uncertainties are compared to the GNSS method. As the authors identify a potential derivation between both methods it remains unclear which one is more absolute accurate. Is it possible to correct the more inaccurate value with the other method?