An Error Prediction Model for Construction Bulk Measurements Using a Customized Low-Cost UAS-LIDAR System

Round 1

Reviewer 1 Report

 This paper discusses a custom-designed low-cost UAS-based LIDAR system that can effectively measure construction excavation and bulk piles. An error model was developed to predict the horizontal and vertical errors of single-point geo-registration for a generic UAS-LIDAR. This model was validated for the proposed UAS-LIDAR system using calibration targets and real-world measurements from different scenarios. The results indicated random errors from LIDAR at approximately 0.1 m and systematic errors at or below the centimeter level.  The result of the developed error model is in good agreement with the performed experiment.  The paper can be published as a journal paper after addressing the below comments.

 

Please define “UAS” in the first place of the text. For example Unmanned Arial System (UAS)

Line 399: Please fix “Error! Reference source not found”

Line 415: Please fix “Error! Reference source not found”

Line 417: Please fix “Error! Reference source not found”

Line 435: Please fix “Error! Reference source not found”

Line 437&438: Please fix “Error! Reference source not found”

Line 443: Please fix “Error! Reference source not found”

Line 444: Please fix “Error! Reference source not found”

Line 454&455: Please fix “Error! Reference source not found”

Line 476: Please fix “Error! Reference source not found”

Line 480: Please address clearly. “the top of which is” is ambiguous.

Line 482: Please fix “Error! Reference source not found”

Line 491: please fix the table description. “Table 3 Height of Tent Target 2 by Measured by LLDAR and GNSS Survey”

Line 499 & 500 & 501: Please fix “Error! Reference source not found”

Line 509&510: Please fix “Error! Reference source not found”

Line 528: Please fix “Error! Reference source not found”

Line 531: Please fix “Error! Reference source not found”

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

Major comments

 

Of late, there have been many surveying studies conducted using unmanned aerial vehicles (UAVs), popularly known as drones. In addition, there are many studies dealing with general airframes. As a result, it is a challenge to differentiate one kind of research from the other. Your study improves the accuracy of surveying through the use of GPS, and  but the mechanism and data logs of your system are unclear and need to be elaborated upon. In addition, the originality and strengths of your study need to be emphasized better.

Errors of the order of centimeters in UAV operation can affect practical use. This is because of a baseline altitude error of approximately 1 m, which manufacturers are also aware of, when the UAV is in flight. Please factor this point into your formulas.

 

1. Introduction

Please add citations to the paragraphs that are based on previous studies. Also include how much the total cost can be reduced, if possible.

 

3. System Design

Although your system is good, UAVs in general pose challenges such the inherent altitude error of approximately 1 m. It would be useful if the interface could be enhanced to control it.

 

Where do you get the power for the terrestrial laser scanner? Since it is not covered under system configuration, please write it up with the accompanying chart.

 

Since the battery is the UAV’s primary power source, changes in voltage can affect the output and should be considered. The presence or absence of the effects of weather should also be considered. If the voltage changes, the detected and recorded values can change.

 

5. Error Model Validation

The accuracy of global navigation satellite systems (GNSS) varies depending on the number of satellites in communication. From that perspective, the accuracy of mm is not in GNSS. The number of satellites to enter should be considered.

 

References

There are published papers that measure the drone’s height or display it in some way. Please reference one of those papers, e.g..,

 

Patrik, A.; Utama, G.; Gunawan, A.; Chowanda, A.; Suroso, J.S.; Shofiyanti, R.; Budiharto, W. GNSS-based navigation systems of autonomous drone for delivering items. J. Big Data 2019, 6, 53.

Orjales, F.; Losada-Pita, J.; Paz-Lopez, A.; Deibe, Á.; Towards Precise Positioning and Movement of UAVs for Near-Wall Tasks in GNSS-Denied Environments. Sensors 2019, 21(6): 2194.

Chiba, T.; Haga, Y.; Inoue, M.; Kiguchi, O.; Nagayoshi, T.; Madokoro, H.; Morino, I. Measuring Regional Atmospheric CO2 Concentrations in the Lower Troposphere with a Non-Dispersive Infrared Analyzer Mounted on a UAV, Ogata Village, Akita, Japan. Atmosphere 2019, 10, 487.

Park, K.; Kim, W.; Seo, J. Effects of Initial Attitude Estimation Errors on Loosely Coupled Smartphone GPS/IMU Integration System. 20th International Conference on Control Automation and Systems (ICCAS). 2020. 800-803,

 

 

Minor comments

 

L52: If it is possible to reduce the cost of this research, please provide that information.

 

L431: You should not show the sentence "Error! Reference source not found" but the interface in PROPORTIONAL CONTROLLER you used in this manuscript with the photo.

 

L393: Can you show in the photo what the altitude displayed in the UAV’s interface looks like? It is strange that the laser survey is constant even though there is a high degree of fluctuation on the UAV side. Please add the description.

 

Figure 2: Please create the chart with more plot points.

 

Figure 3: Please add a scale to the photos in Figure 3.

 

Figure 4: Please show the actual cement-concrete size of the target triangles.

 

Figure 3, 6 and 11: Show the actual measurement size (cm) of each target in New table.

 

Figure 7-9: Why is the measured value biased toward the lower side (smaller magnitudes)? Is it a measurement feature?

 

Figure 11: Please add a scale to the photo.

 

Table 3: The accuracy of GNSS surveying depends on the number of satellites that enter. From that point, the accuracy of mm is not in GNSS. The number of satellites to enter should be considered.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The Matrice 600 Pro is equipped with an altitude display system calculated from a barometer. If the barometric pressure changes, the altitude displayed on the proportional controller may differ from the measured value (e.g. GNSS). In that respect, it should be pointed out that the stability of the UAV in flights cannot be relied on very much. Whether the elevation accuracy shown in this study is possible with drones may continue to be debated. Of course, in this paper, you also used measurement methods that does not depend on the flight altitude of the UAV, so the effect may be small.

On the other hand, it seemed that one of the future tasks is to devise a method for correcting the measured values between TLS and UAS-LIDAR.

Author Response

Please see the attachment.

Author Response File: Author Response.docx