Experimental Investigation on the Performance of DJI Phantom 4 RTK in the PPK Mode for 3D Mapping Open-Pit Mines

Open-pit coal mines’ terrain is often complex and quickly and frequently changes. Therefore, topographic surveys of open-pit mines are undertaken on a daily basis. While these tasks are very time-consuming and costly with traditional methods such as total station and GNSS, the unmanned aerial vehicle (UAV) based method can be more efficient. This method is a combination of the “Structure from motion” (SfM) photogrammetry technique and UAV photogrammetry which has been widely used in topographic surveying. With an increasing popularity of RTK-enabled drones, it is becoming even more powerful method. While the important role of ground control points (GCP) in the accuracy of digital surface model (DSM) generated from images acquired by “traditional” UAVs (not RTK-enabled drones) has been proved in many previous studies, it is not clear in the case of RTK-enabled drones, especially for complex terrain in open-pit coal mines. In this study, we experimentally investigated the influence of GCP regarding its numbers and distribution on the accuracy of DSM generation from images acquired by RTK-enabled drones in open-pit coal mines. In addition, the Post Processing Kinematic (PPK) mode was executed over a test field with the same flight altitude. DSM generation was performed with several block control configurations: PPK only, PPK with one GCP, and PPK with two GCPs. Several positions of GCPs were also examined to test the optimal locations for placing GCPs to achieve accurate DSMs. The results show that the horizontal and vertical accuracy given by PPK only were 9.3 and 84.4 cm, respectively. However, when adding at least one GCP, the accuracy was significantly improved in both horizontal and vertical components, with RMSE for XY and Z ranging between 3.8 and 9.8 cm (with one GCP) and between 3.0 and 5.7 cm (with two GCPs), respectively. Also, the GCPs placed in the deep areas of the open-pit mine could ensure the cm-level accuracy.

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Accuracy assessment of open - pit mine’s digital surface models generated using photos captured by Unmanned Aerial Vehicles in the post - processing kinematic mode

Journal of Mining and Earth Sciences ◽

10.46326/jmes.2021.62(4).05 ◽

2021 ◽

Vol 62 (4) ◽

pp. 38-47

Author(s):

Long Quoc Nguyen ◽

Keyword(s):

Accuracy Assessment ◽

Open Pit ◽

Ground Control ◽

Surface Model ◽

Control Points ◽

Post Processing ◽

Ground Control Points ◽

Satellite Positioning ◽

Surface Models ◽

Aerial Vehicle

To evaluate the accuracy of the digital surface model (DSM) of an open-pit mine produced using photos captured by the unmanned aerial vehicle equipped with the post-processing dynamic satellite positioning technology (UAV/PPK), a DSM model of the Deo Nai open-pit coal mine was built in two cases: (1) only using images taken from UAV/PPK and (2) using images taken from UAV/PPK and ground control points (GCPs). These DSMs are evaluated in two ways: using checkpoints (CPs) and comparing the entire generated DSM with the DSM established by the electronic total station. The obtained results show that if using CPs, in case 1, the errors in horizontal and vertical dimension were 6.8 and 34.3 cm, respectively. When using two or more GCPs (case 2), the horizontal and vertical errors are at the centimetre-level (4.5 cm and 4.7 cm); if using the DSM comparison, the same accuracy as case 2 was also obtained.

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Building DEM for deep open-pit coal mines using DJI Inspire 2

Journal of Mining and Earth Sciences ◽

10.46326/jmes.2020.61(1).01 ◽

2020 ◽

Vol 61 (1) ◽

pp. 1-10

Author(s):

Nguyen Viet Nghia ◽

Keyword(s):

3D Model ◽

Coal Mines ◽

Image Data ◽

Maximum Error ◽

3D Models ◽

Reference Points ◽

Open Pit ◽

Open Pit Mines ◽

Aerial Vehicle ◽

Uav Image

Using photo data of unmanned aerial vehicle (UAV) for building 3D models has been widely used in recent years. However, building a 3D model for deep open - pit coal mines with the mean height difference between surface and bottom of mines to over 500 m, there has not been researched mentioned. The paper deals with the assessment possibility of developing 3D models for deep open - pit mines from UAV image data. To accomplish this goal, DJI's Inspire 2 flying device is used to take the photo at Coc Sau coal mine. The flying area is 4 km2, the flight altitude compared to the takeoff point on the mine surface is 250 m, the overlaying coverage is both horizontal and vertical is 70%. The average errors of the horizontal and height elements of the reference points photo correlates are 0.011 m, 0.017 m, 0.016 m, 0.049 m, and 0.051 m. The maximum error on the X-axis is - 0,025 m, and the Y-axis is 0.028 m, the maximum horizontal error is 0.034 m, the maximum error on the Z-axis is 0.095 m, and the position error is 0.095 m. These results show that the 3D model established from photographic data by Inspire 2 device has satisfied the requirements of the accuracy of establishing the mining terrain map 1: 1000 scale.

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Research on optimal takeoff positions of UAV integrated GNSS - RTK in producing large scale topological maps for open - pit mines

Journal of Mining and Earth Sciences ◽

10.46326/jmes.2020.61(5).06 ◽

2020 ◽

Vol 61 (5) ◽

pp. 54-63

Author(s):

Canh Van Le ◽

Cuong Xuan Cao ◽

Ha Thu Thi Le ◽

Keyword(s):

Large Scale ◽

Low Cost ◽

Open Pit ◽

Surface Model ◽

Open Pit Mines ◽

Topological Maps ◽

Accuracy Requirement ◽

Ground Control Points ◽

Uav Images ◽

A Site

Unmanned aerial vehicles (UAV) are widely used for establishing large scale topological maps. Recently, drones have been integrated with high-quality GNSS receivers which allows real time kinematic positioning (RTK), so are called UAV/RTK. This technology is beneficial to surveyors as they do not need to establish many ground control points in mapping such a complex terrain as open-pit mines. DJI Phantom 4 RTK (P4K) is a UAV/RTK which is of much interest due to its small size and low cost. For open-pit mines, the takeoff position of P4K needs to be seriously considered because of its influence on the accuracy of the digital surface model (DSM) and safety of survey flights. This article presents the method of determining the optimal takeoff positions for UAV in large scale mapping for open pit mines. To evaluate this method, a site of steep and rugged terrain with an area of 80 hectares at the Coc Sau coal mine was chosen as the study area. The results indicate that two optimal locations with altitudes of +50 m and +160 m could be used for taking off the P4K. The accuracy of DSM generated from UAV images using the optimal positions satisfied the accuracy requirement of large scale topological maps at the deepest area of the mine (the altitude of -60 m).

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UAV PHOTOGRAMMETRY-BASED FOR OPEN PIT COAL MINE LARGE SCALE MAPPING, CASE STUDIES IN CAM PHA CITY, VIETNAM

Sustainable Development of Mountain Territories ◽

10.21177/1998-4502-2020-12-4-501-509 ◽

2020 ◽

Vol 12 (4) ◽

pp. 501-509

Author(s):

Nguyen Long ◽

◽

Le Thi Thu Ha ◽

Tong Si Son ◽

Kim Thi Thu Huong ◽

...

Keyword(s):

Large Scale ◽

Coal Mines ◽

Open Pit ◽

Ground Control ◽

Surface Model ◽

Control Points ◽

Aerial Photogrammetry ◽

Ground Control Points ◽

Active Coal ◽

Uav Images

The use of lightweight Unmanned Aerial Vehicle with the aerial photogrammetry approach to construct the Digital Surface Model (DSM) has been effectively applied for various types of topography. However, the ability to carry out this approach for huge active open coal mines is insufficiently investigated, furthermore, the influences of topographical factors on the accuracy of DSM are ambiguous. This experiment attempts to apply the UAV method for the two active coal mines with the total area of 7.99 km2 , exploited at a range from -300 m to 300 m altitude to figure out the effect of topographic factors on the accuracy of DEM constructed from UAV images. A total of 972 UAV images and 17 ground control points have been coupled to construct DSM of the mines. Besides, 16 checking points located at different elevations are used to evaluate the accuracy of DEM and to define the influence. DEMs are generated with the maximum RMSE of 0.086 m, 0.099 m, and 0.170 m corresponding to X, Y, and Z dimensional errors. The results show the unclear correlation between the vertical accuracy of DEM and the relative elevation (R2=0.064), the general slope of the mines, and the number of ground control points using in the coal mines as well.

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Influence of Flight Height on The Accuracy of UAV Derived Digital Elevation Model at Complex Terrain

Inżynieria Mineralna ◽

10.29227/im-2020-01-27 ◽

2020 ◽

Vol 1 (1) ◽

Author(s):

Nguyen QUOC LONG ◽

Ropesh GOYAL ◽

Bui KHAC LUYEN ◽

Le VAN CANH ◽

Cao XUAN CUONG ◽

...

Keyword(s):

Complex Terrain ◽

Mining Industry ◽

Open Pit ◽

Control Points ◽

Open Pit Mines ◽

Ground Control Points ◽

Digital Elevation ◽

Flight Height ◽

Aerial Vehicle ◽

Elevation Model

Lightweight Unmanned Aerial Vehicle (UAV) for 3D topographic mapping in mining industry has been raised significantly in recent years. Especially, in complex terrains such as in open-pit mines in which the elevation is rapidly undulating, UAV-based mapping has proven its economical efficiency and higher safety compared to the conventional methods. However, one of the most important factors in UAV mapping of complex terrain is the flight altitude, which needs to be considered seriously because of the safety and accuracy of generated DEMs. This paper aims to evaluate the influence of the flight height on the accuracy of DEMs generated in open-pit mines. To this end, the study area is selected in a quarry with a complex terrain, which is located in northern Vietnam. The investigation was conducted with five flight heights of 50 m, 100 m, 150 m, 200 m, and 250 m. To assess the accuracy of resulting DEMs, ten ground control points (GCPs), and 385 checkpoints measured by both GNSS/RTK and total station methods were used. The accuracy of DEM was assessed by root-mean-square error (RMSE) in X, Y, Z, XY, and XYZ components. The results show that DEM models generated at the flight heights of less than 150 m have high accuracy. RMSEs of the 10 GCPs increase from 1.8 cm to 6.2 cm for the vertical (Z), and from 2.6 cm to 6.3 cm for the horizontal (XY), whereas RMSE of 385 checkpoints increase gradually from 0.05 m to 0.15 m for the vertical (Z) when the flight height increases from 50 m to 250 m.

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Determining the ability to receive rock of waste dumps when exploiting a group of open-pit coal mines

Journal of Mining and Earth Sciences ◽

10.46326/jmes.ktlt2020.06 ◽

2020 ◽

Vol 61 (5) ◽

pp. 71-79

Author(s):

Hoan Ngoc Do ◽

Fomin Sergey Igorevic ◽

Keyword(s):

Waste Disposal ◽

Coal Mines ◽

Open Pit ◽

Environmental Restoration ◽

Open Pit Mines ◽

Waste Dumps ◽

Geological Conditions ◽

Restoration Work ◽

Transportation Flows ◽

To Receive

In the process of developing the general exploitation and disposal plan for the Deonai, CocSau and Caoson coal mines, use should be taken into account the maximum internal disposal sites to reduce the transport supply and facilitate the environmental restoration work after exploitation. However, in the geological conditions of these coal mines, in order to ensure the space to exploit and make full use of useful minerals, it is necessary to calculate the economic efficiency when building the exploitation and disposal plan. The content of the article is based on the criteria of optimum transportation flows of rock in the arrangement of waste disposal when exploiting a group of three open-pit mines Deo Nai, Coc Sau and Cao Son.

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Detecting drainage pitfalls in open-pit mines and haul roads using UAV-photogrammetry

DYNA ◽

10.15446/dyna.v88n216.90801 ◽

2021 ◽

Vol 88 (216) ◽

pp. 190-195

Author(s):

Felipe Dille Benevenuti ◽

Rodrigo De Lemos Peroni

Keyword(s):

Three Dimensional ◽

Open Pit ◽

Road Maintenance ◽

Open Pit Mines ◽

Cycle Times ◽

Course Material ◽

Aerial Vehicle ◽

Haul Road ◽

Elevation Model

Open-pit mines generally have operational problems such as puddling and inappropriate water flow over haul roads, particularly if located in areas with high rainfall indices. These situations increase truck cycle times, promote rapid deterioration of haul-road wearing-course material, reduce productivity due to downtime and increase road maintenance. In addition, operational costs are raised as the frequency of truck maintenance and tire failures also increase. The use of a high-resolution three-dimensional elevation model, created based on Unmanned Aerial Vehicle (UAV) photogrammetry, has been shown to be an effective technique to detect anomalies in a fast and precise way. With the proposed approach, it is possible to diagnose haul-road conditions after rainfall or to anticipate the potential occurrence of such anomalies before they become a greater problem. This diagnosis can then be used to prioritize maintenance activities in open-pit mines. To describe the methodology, a case study is presented demonstrating and validating the results obtained.

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Improvement of Workflow for Topographic Surveys in Long Highwalls of Open Pit Mines with an Unmanned Aerial Vehicle and Structure from Motion

Remote Sensing ◽

10.3390/rs13173353 ◽

2021 ◽

Vol 13 (17) ◽

pp. 3353

Author(s):

Ignacio Zapico ◽

Jonathan B. Laronne ◽

Lázaro Sánchez Castillo ◽

José F. Martín Duque

Keyword(s):

Structure From Motion ◽

Open Pit ◽

Mining Areas ◽

Camera Angle ◽

Flight Mode ◽

Aerial Vehicle ◽

Computer Based ◽

Kaolin Mine ◽

Oblique Images ◽

Topographic Surveys

Conducting topographic surveys in active mines is challenging due ongoing operations and hazards, particularly in highwalls subject to constant and active mass movements (rock and earth falls, slides and flows). These vertical and long surfaces are the core of most mines, as the mineral feeding mining production originates there. They often lack easy and safe access paths. This framework highlights the importance of accomplishing non-contact high-accuracy and detailed topographies to detect instabilities prior to their occurrence. We have conducted drone flights in search of the best settings in terms of altitude mode and camera angle, to produce digital representation of topographies using Structure from Motion. Identification of discontinuities was evaluated, as they are a reliable indicator of potential failure areas. Natural shapes were used as control/check points and were surveyed using a robotic total station with a coaxial camera. The study was conducted in an active kaolin mine near the Alto Tajo Natural Park of East-Central Spain. Here the 140 m highwall is formed by layers of limestone, marls and sands. We demonstrate that for this vertical landscape, a facade drone flight mode combined with a nadir camera angle, and automatically programmed with a computer-based mission planning software, provides the most accurate and detailed topographies, in the shortest time and with increased flight safety. Contrary to previous reports, adding oblique images does not improve accuracy for this configuration. Moreover, neither extra sets of images nor an expert pilot are required. These topographies allowed the detection of 93.5% more discontinuities than the Above Mean Sea Level surveys, the common approach used in mining areas. Our findings improve the present SfM-UAV survey workflows in long highwalls. The versatile topographies are useful for the management and stabilization of highwalls during phases of operation, as well closure-reclamation.

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