the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 12 May 2022
Drone-towed CSEM system for near-surface geophysical prospecting: On instrument noise, temperature drift, transmission frequency and survey setup
Abstract. Drone-borne controlled source electromagnetic (CSEM) systems combine the mobility of airborne systems with the high subsurface resolution in ground systems. As such, drone-borne systems are beneficial at sites with poor accessibility and in areas where high resolution is needed, e.g., for archaeological or subsurface pollution investigations. However, drone-borne CSEM systems are associated with challenges, which are not observed to same the degree in airborne or ground surveys. In this paper, we explore some of these challenges based on an example of a new drone-towed CSEM system. The system deploys a multi-frequency broadband electromagnetic sensor (GEM-2UAV), which is towed six meters below a drone in a towing-bird configuration together with a Novatel GNSS-IMU unit, enabling centimetre level position precision and orientation. The results of a number of controlled tests of the system are presented together with data from an initial survey at Falster (Denmark), including temperature drift, altitude vs signal, survey mode signal dependency, and the effect of frequency choice on noise. The test results reveal the most critical issues for our system and issues that are likely encountered in similar drone-towed CSEM setups. We find that small altitude variations (+/- 0.5 m) along our flight paths drastically change the signal, and a local height vs signal correlation is needed to correct near-surface drone-towed CSEM data. The highest measured impact was -46.2 ppm/cm for a transmission frequency of 91 kHz. We also observe a significant increase in the standard deviation of the noise level up to 500 % when going from one transmission frequency to five. We recommend not to use more than three transmission frequencies, and the lowest transmission frequencies should be as high as the application allows it. Finally, we find a strong temperature dependency (up to 32.2 ppm/C), which is not accounted for in the instrumentation.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(5867 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(5867 KB) - Metadata XML
- BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2022-217', Anonymous Referee #1, 01 Oct 2022
The present paper introduces the use of a drone-towed CSEM system. The system was used under several configurations in order to minimize noise and increase its accuracy. Authors identified a number of criticalities in the use of such systems, but there are clearly potential in its use.
Nevertheless, I think that the manuscript requires significant effort in order to be published. In particular, I have identified the following major issues:
- The manuscript is too technical from my point of view. The advances obtained with this research are not clearly emphasized. An effort in this direction would be very much appreciated.
- It would be good to use the analysis carried out in the present study to build a workflow with clear guidelines about the best strategies to be used in order to increase the quality of the system.
- Discussion of the manuscript should be extended including some more details about the advantages/disadvantages, and potential uses of the drone-towed CSEM system.
Citation: https://doi.org/10.5194/egusphere-2022-217-RC1 -
AC1: 'Reply on RC1', Tobias Bjerg Vilhelmsen, 05 Oct 2022
Thanks for the feedback. That is greatly appreciated. You have some valid points, and I will find a way to implement them. I may come up with some follow-up questions later.
Citation: https://doi.org/10.5194/egusphere-2022-217-AC1 -
AC2: 'Reply on RC1', Tobias Bjerg Vilhelmsen, 08 Nov 2022
Dear Anonymous Referee #1
Once again, thanks for the feedback. I have discussed it with my co-author and made some changes which I will upload in a revised manuscript that hopefully fulfils your requests.
Response to your comments:
- We know it is a rather technical manuscript, but we considered this specific forum suited for more technical papers. So we prefer to keep the technical details for now. Apart from the too-technical part, we have emphasised the advances obtained in the discussion.
- At the end of the discussion, we have included our guidelines for the best strategies in a bullet point format to gain a better overview.
- We have changed quite a bit in the discussion, including more detail on the advantages/disadvantages.
Citation: https://doi.org/10.5194/egusphere-2022-217-AC2
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EC1: 'Comment on egusphere-2022-217', Lev Eppelbaum, 01 Oct 2022
As Assoc. Editor, I am glad to see that the discussion is continued.
Citation: https://doi.org/10.5194/egusphere-2022-217-EC1 -
CC1: 'Comment on egusphere-2022-217', Danil Sapronov, 07 Oct 2022
Dear Lev Eppelbaum,
I have read your preprint and it interested me a lot.
I am a newbee in Drone-towed CSEM systems, so I am more like electrical engineer who is trying to understand how they work.
Could you please give me some technical details of your UAV basaed device to help me figure it out.Best regards,
Danil Sapronov
Citation: https://doi.org/10.5194/egusphere-2022-217-CC1 -
RC2: 'Comment on egusphere-2022-217', Anonymous Referee #2, 07 Oct 2022
In its present form the paper introduces the methodology of using a CSEM system from a UAV/drone. It covers a number of different configuration settings and presents the collected data along with identification on system performance due to instrument noise, temperature drift, transmission frequency and overall survey setup. The paper has value to future users of UAV flown CSEM systems as well as the community that uses this data. In time UAV will start to be the platform of choice and such CSEM systems will overcome the observed effects on data quality to a level that the science and industry communities can trust the data as much as their current methods. Also the paper gives a good basis for future research and development of UAV CSEM platforms. In conclusion this paper would be beneficial to the research community and clearly the sensors once fully developed have clear potential to be used for geophysics on a regular basis.
None the less the paper in its present form could be improved greatly and be of greater value to the community, though this will involve reasonably extensive restructuring and addition prior to publishing. I detail below the main issues:
- The paper is very method heavy and at points repetitive, I would like to see more focus on the comparison of the data collected against either a baseline data set or data collected in the conventional way by ground methods or aerial methods from helicopters or aircraft. Once the comparison is made the observed effects from temperature etc. effect the measurement/data collection could be quantitatively and qualitatively assessed against current methods and how much work is required to get equivalence or near enough to be a useful trusted method. This would be very useful for future research either by the authors or other researchers.
- More context initially of the advantages and disadvantages of the studied system against the current systems used to collect EM data would help provide context for later discussion of the results.
- With more analysis and comparison to systems currently used, a conclusion could be drawn on how far away in data quality the studied system is from those currently used. Having the comparison would also start to indicate how the system could be improved, whether this is by method of use, system improvements, enhanced processing, or by using additional data to provide models for correcting the EM data such as a temperature based calibration table.
Citation: https://doi.org/10.5194/egusphere-2022-217-RC2 -
AC3: 'Reply on RC2', Tobias Bjerg Vilhelmsen, 08 Nov 2022
Dear Anonymous Referee #2
Thanks a lot for the feedback; it is very valuable. I have discussed it with my co-author and made some changes which I will upload in a revised manuscript that hopefully fulfils your requests.
Response to your comments:
- At this point, we do not have any other (aerial) baseline data to compare it with, and we can only refer to other articles as we do in the manuscript. Nonetheless, we include a lot of data that indicate the instrumentation noise in a static mode, which can help us evaluate the drone-towed solution. We know it is a method-heavy manuscript, but we considered this specific forum suited for more technical and method-heavy papers. So we prefer to keep the technical details for now.
- Most of the introduction describes the advantages and disadvantages of the other EM system, but we have made extensive changes in the discussion to further emphasised the advantages/disadvantages.
- At the end of the discussion, we have included our guidelines for the best strategies in a bullet point format, which can help implement possible improvements.
Citation: https://doi.org/10.5194/egusphere-2022-217-AC3
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-217', Anonymous Referee #1, 01 Oct 2022
The present paper introduces the use of a drone-towed CSEM system. The system was used under several configurations in order to minimize noise and increase its accuracy. Authors identified a number of criticalities in the use of such systems, but there are clearly potential in its use.
Nevertheless, I think that the manuscript requires significant effort in order to be published. In particular, I have identified the following major issues:
- The manuscript is too technical from my point of view. The advances obtained with this research are not clearly emphasized. An effort in this direction would be very much appreciated.
- It would be good to use the analysis carried out in the present study to build a workflow with clear guidelines about the best strategies to be used in order to increase the quality of the system.
- Discussion of the manuscript should be extended including some more details about the advantages/disadvantages, and potential uses of the drone-towed CSEM system.
Citation: https://doi.org/10.5194/egusphere-2022-217-RC1 -
AC1: 'Reply on RC1', Tobias Bjerg Vilhelmsen, 05 Oct 2022
Thanks for the feedback. That is greatly appreciated. You have some valid points, and I will find a way to implement them. I may come up with some follow-up questions later.
Citation: https://doi.org/10.5194/egusphere-2022-217-AC1 -
AC2: 'Reply on RC1', Tobias Bjerg Vilhelmsen, 08 Nov 2022
Dear Anonymous Referee #1
Once again, thanks for the feedback. I have discussed it with my co-author and made some changes which I will upload in a revised manuscript that hopefully fulfils your requests.
Response to your comments:
- We know it is a rather technical manuscript, but we considered this specific forum suited for more technical papers. So we prefer to keep the technical details for now. Apart from the too-technical part, we have emphasised the advances obtained in the discussion.
- At the end of the discussion, we have included our guidelines for the best strategies in a bullet point format to gain a better overview.
- We have changed quite a bit in the discussion, including more detail on the advantages/disadvantages.
Citation: https://doi.org/10.5194/egusphere-2022-217-AC2
-
EC1: 'Comment on egusphere-2022-217', Lev Eppelbaum, 01 Oct 2022
As Assoc. Editor, I am glad to see that the discussion is continued.
Citation: https://doi.org/10.5194/egusphere-2022-217-EC1 -
CC1: 'Comment on egusphere-2022-217', Danil Sapronov, 07 Oct 2022
Dear Lev Eppelbaum,
I have read your preprint and it interested me a lot.
I am a newbee in Drone-towed CSEM systems, so I am more like electrical engineer who is trying to understand how they work.
Could you please give me some technical details of your UAV basaed device to help me figure it out.Best regards,
Danil Sapronov
Citation: https://doi.org/10.5194/egusphere-2022-217-CC1 -
RC2: 'Comment on egusphere-2022-217', Anonymous Referee #2, 07 Oct 2022
In its present form the paper introduces the methodology of using a CSEM system from a UAV/drone. It covers a number of different configuration settings and presents the collected data along with identification on system performance due to instrument noise, temperature drift, transmission frequency and overall survey setup. The paper has value to future users of UAV flown CSEM systems as well as the community that uses this data. In time UAV will start to be the platform of choice and such CSEM systems will overcome the observed effects on data quality to a level that the science and industry communities can trust the data as much as their current methods. Also the paper gives a good basis for future research and development of UAV CSEM platforms. In conclusion this paper would be beneficial to the research community and clearly the sensors once fully developed have clear potential to be used for geophysics on a regular basis.
None the less the paper in its present form could be improved greatly and be of greater value to the community, though this will involve reasonably extensive restructuring and addition prior to publishing. I detail below the main issues:
- The paper is very method heavy and at points repetitive, I would like to see more focus on the comparison of the data collected against either a baseline data set or data collected in the conventional way by ground methods or aerial methods from helicopters or aircraft. Once the comparison is made the observed effects from temperature etc. effect the measurement/data collection could be quantitatively and qualitatively assessed against current methods and how much work is required to get equivalence or near enough to be a useful trusted method. This would be very useful for future research either by the authors or other researchers.
- More context initially of the advantages and disadvantages of the studied system against the current systems used to collect EM data would help provide context for later discussion of the results.
- With more analysis and comparison to systems currently used, a conclusion could be drawn on how far away in data quality the studied system is from those currently used. Having the comparison would also start to indicate how the system could be improved, whether this is by method of use, system improvements, enhanced processing, or by using additional data to provide models for correcting the EM data such as a temperature based calibration table.
Citation: https://doi.org/10.5194/egusphere-2022-217-RC2 -
AC3: 'Reply on RC2', Tobias Bjerg Vilhelmsen, 08 Nov 2022
Dear Anonymous Referee #2
Thanks a lot for the feedback; it is very valuable. I have discussed it with my co-author and made some changes which I will upload in a revised manuscript that hopefully fulfils your requests.
Response to your comments:
- At this point, we do not have any other (aerial) baseline data to compare it with, and we can only refer to other articles as we do in the manuscript. Nonetheless, we include a lot of data that indicate the instrumentation noise in a static mode, which can help us evaluate the drone-towed solution. We know it is a method-heavy manuscript, but we considered this specific forum suited for more technical and method-heavy papers. So we prefer to keep the technical details for now.
- Most of the introduction describes the advantages and disadvantages of the other EM system, but we have made extensive changes in the discussion to further emphasised the advantages/disadvantages.
- At the end of the discussion, we have included our guidelines for the best strategies in a bullet point format, which can help implement possible improvements.
Citation: https://doi.org/10.5194/egusphere-2022-217-AC3
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Tobias Bjerg Vilhelmsen
Arne Døssing
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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