the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 29 May 2026
Rapid detection of centimeter-scale change in a Mars analog environment using ground-based mobile LiDAR
Abstract. Landed missions to dynamic planetary surfaces require tools capable of measuring the small-scale topographic changes driven by active surface processes. A ground-based LiDAR scanner is one of the few instruments capable of detecting the centimeter-scale changes that are expected due to both natural processes such as wind erosion and sedimentary reworking, as well as artificial processes resulting from robotic/human exploration. At landing site scales, a ground-based LiDAR scanner on a mobile platform can collect cm-scale topographic information more efficiently than using a scanner on a stationary mount. To demonstrate the viability of mobile LiDAR for planetary missions, we conducted scans at a Mars analog site in central Iceland. Scans before and after a windstorm detected erosion and deposition of sand on the order of a few cm, with a detection threshold of ~1 cm. The ability of the mobile platform to collect data over extremely short timescales (<30 minutes) made it possible to conduct spontaneous scans to record opportunistic targets after the windstorm, while maintaining cm-scale resolution. This makes a compelling case for the inclusion of mobile LiDAR on future missions to explore planetary surfaces such as the Moon, Mars and Titan.
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RC1: 'Comment on egusphere-2026-2733', Anonymous Referee #1, 01 Jun 2026
- The topic is very interesting and relevant, good introduction into it.
- There is no GNSS on Mars. That (and the consequences) should already be mentioned in the introduction, not only in the discussion at the end.
- Why was the Riegl VUX-1HA chosen? Is 1550 nm the ideal wavelength for the purpose? Why didn’t you choose a scanner with phase shift based distance measurement, which should provide significantly better distance measurement precision?
- 2.1: Why is it necessary to manually pick point pairs in two datasets here? With very good approximate valuas available, multi-temporal point cloud registration could easily be automated, see for instance the ISPRS Com. II proceedings 2024 (https://isprs-annals.copernicus.org/articles/X-2-2024.
- The results look good on first glimpse. However, a detailed analysis of precision and reliability id missing. You mention cm-precision, but is that really substantiated by the results? Especially, it would have been nice to have independent external reference measurements, which shouldn’t be too difficult in such a study on Earth.
- I found the statements on the possibilities of registration in GNSS-denied settings too vague, especially concerning the effects on the desired cm-precision. Why were these alternatives not examined in the study? And could SLAM be an option?
Citation: https://doi.org/10.5194/egusphere-2026-2733-RC1 -
RC2: 'Comment on egusphere-2026-2733', Anonymous Referee #2, 30 Jun 2026
The manuscript presents an interesting field study using a backpack-mounted mobile LiDAR system to measure centimeter-scale dune migration at a site in Holuhraun (Iceland). The data collection is robust, and the terrestrial topographic processing is well applied. However, the manuscript's main scientific justification—that it is a Mars analog demonstration—is not sufficiently supported by the methods and approach used. In its current state, the article documents a conventional terrestrial surveying application without addressing the actual constraints of a planetary mission.
I recommend rejecting the manuscript in its current form. However, I strongly encourage the authors to reprocess their existing data to simulate realistic planetary constraints and resubmit the manuscript, as the underlying dataset has great potential.
Major Comments:
The proposed technical methodology (mobile LiDAR) and the change-detection algorithms (M3C2) are mature and widely documented in the literature. The presented results are exactly what is expected from a high-end commercial instrument like the Riegl VUX-1HA. Thus, the paper does not present an instrumental or algorithmic breakthrough. Furthermore, the methodology should be improved or justified in the following areas:
- The authors should justify the use of the Riegl VUX-1HA (a time-of-flight scanner). For centimeter-to-millimeter precision at close range, phase-shift scanners typically provide better distance measurement precision, although this comes at the cost of a shorter maximum range. The choice of instrument should still be briefly justified in the text, even if range and portability are the reason.
- Registration is done using nine manually picked point pairs. This works, but it is a highly outdated approach. With good approximate values available, multi-temporal point cloud registration should be automated to avoid user bias and improve reproducibility
- The claimed cm-level precision is entirely based on relative cloud-to-cloud distances. But independent ground control points were not used. These would have been easy to set up in this terrestrial field site and would allow direct validation of the precision, instead of relying only on internal comparison. This is especially important, since the precision value highlighted as a key result is exactly what an external validation would need to confirm.
However, the novelty of this paper relies on the use of this instrument in a Mars-analog environment. But the study fails to address the realities of deploying such a system on Mars. This is evident in several critical areas:
- The authors achieve their absolute precision and trajectory mapping using a GNSS antenna and a reference station. Mars does not have a GPS network. The authors address this point in the Discussion, where they note that GNSS-denied LiDAR mapping techniques exist and cite prior work, including their own, on this topic. However, this discussion is not reflected in the data or methods presented in this study, as the dataset itself still relies on GNSS for its results; the claim of Mars-relevant precision is therefore discussed but not actually demonstrated.
- This constraint should also be explicitly stated in the Introduction, not only in the discussion. To prove this concept works for planetary science, the authors should have processed their raw data without the GNSS input, relying solely on the IMU and SLAM algorithms, to demonstrate if the required cm-level precision can actually be maintained in a GNSS-denied environment.
- The 175 m² region of interest produced over 5 million points. The manuscript does not discuss the data volume problem for deep-space communication. Deep space communications have severe bandwidth limitations, and raw LiDAR point clouds are incredibly data-heavy.
- A mobile backpack scanner does not reflect the severe constraints of a rover. The authors do not address the high energy consumption required to run a continuous laser scanner, nor the physical size and weight limitations that are critical in spaceflight engineering.
- Also, a human operator provides a completely different vantage point, walking speed, and vibration dampening compared to a rigid, slow-moving rover. Additionally, in a terrestrial analog, a human operator will naturally shelter the LiDAR equipment during a severe windstorm to protect it. On Mars, the instrument cannot be put away; it would be continuously exposed to harsh environmental conditions, abrasive dust, and intense winds, which calls into question the operational durability of the proposed setup.
So, in general the change-detection result itself is solid science but not novel. This paper could have a significant scientific impact if it shifts its focus: rather than demonstrating that "commercial LiDAR can detect millimeter changes on Earth," it should explore "how Martian constraints degrade the capability of LiDAR to detect changes."
I highly encourage the authors to resubmit a revised version of this paper that performs adapted simulations on their existing data. A few examples:
- Process the trajectory without GNSS (IMU/SLAM only) to calculate the accumulated error.
- Perform massive downsampling on the point clouds to simulate the lighter file sizes dictated by deep-space data transmission limits.
- Adjust the point density and perspective to match a slow-moving rover (or install the system in a small rover simulator)
If the authors can demonstrate that cm-scale change detection is still possible under these artificially impoverished, Mars-simulated conditions, the manuscript would be an exceptionally valuable contribution.
Citation: https://doi.org/10.5194/egusphere-2026-2733-RC2
Data sets
Backpack LiDAR scans from a sand covered lava margin at Holuhraun (Iceland) Vanga, S., Perkins, R. P., Neish, C. D., Zanetti, M. R., Carr, B. B. and Hamilton, C. W. https://doi.org/10.5069/G92805VK
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