# Use of UAV Images in 3D Modelling of Waste Material Stock-Piles in an Abandoned Mixed Sulphide Mine in Mathiatis—Cyprus

^{1}

^{2}

^{*}

## Abstract

**:**

^{3}, approximately.

## 1. Introduction

^{3}. Based on the present investigation, the area is considered suitable for further investigation to be exploited in the future.

## 2. Geology of Cyprus (of the Study Area)

## 3. Stockpile Volume Estimation

#### 3.1. Proposed Methodology Plan

- The stockpile’s boundary was digitised by visual inspection on the point cloud.
- The points of the stockpile’s boundary combined with drillhole data were imported into the GEOVIA Surpac database to build a pseudo-3D block model (BM) The estimation parameter is the elevation Z since the z coordinate of imported data and blocks centroid is dummy (zero).
- After statistical and geostatistical analysis, estimates of elevation (here treated as a BM attribute) were calculated into each BM’s centroid using the Kriging technique.
- These elevation estimates were validated using Kriging residual statistics described analytically in Section 3.6 as proposed by [17,18]. If the Kriging validation failed, then corrections of the Block Kriging model variables were made, and the elevation estimations were repeated.
- After successful validation of Kriging, X, Y of the BM centroids along with the elevation estimated variable as Z were used as input data (points) for the bottom stockpile’s DTM.

#### 3.2. Topographic Map Creation

#### 3.3. Drillhole Data Database

#### 3.4. Statistcal—Geostatistical Analysis

#### 3.5. Block Model of the Study Area

#### 3.6. Validation of Block Model Estimates

- ${Q}_{1}$ value

- ${Q}_{2}$ value

#### 3.7. Block Model Elevation and Variance Estimates

_{2}residual statistic constraint was not met. A second Scenario II, was implemented to remove a polynomial trend (Equation (1)), as described in Section 3.4. In Scenario II, after the first estimation of Z transformed data into every block of the BM, data from drillhole NMMT_BH19 were inserted into the calculations, and the Kriging algorithm was executed again (Figure 10b). New estimates for elevation were carried out, and new errors were calculated. This procedure was continued until all drillhole data were inserted into calculations, and all errors were estimated for every step (Figure 10c–h). The drillhole data import sequence was NMMT_BH18, NMMT_BH19, NMMT_BH21, NMMT_BH22, NMMT_BH20, NMMT_BH17, as displayed in Figure 10b–h.

**Figure 10.**BM plans presenting the elevation (transformed) distribution as data from drillholes are imported into the Kriging algorithm when (

**a**) no drillholes are used, (

**b**) NMMT_BH18 is added to (

**a**,

**c**) NMMT_BH19 is added to (

**b**,

**d**) NMMT_BH21 is added to (

**c**,

**e**) NMMT_BH22 is added to (

**d**,

**f**) NMMT_BH20 is added to (

**e**,

**g**) NMMT_BH17 is added to (

**f**,

**h**) colormap legend.

_{1}and Q

_{2}constraints were met (Figure 12), the construction of the lower TF surface and the stockpile’s volume estimation was done. The Kriging variance of the final Z transformed values (Figure 10g) is presented below After the validation of Z predictions, the X, Y, and Z-predicted values of each BM’s centroid were now used as a point for the creation of the bottom stockpile’s surface. This means that the number of points that was used for the bottom stockpile’s surface is the same, with the number of the block shown in Figure 10 and Figure 11 (inside the red line).

_{1}< 0) and overestimates the error (Q

_{2}< 1), which can be enhanced by further reducing the semivariogram sill value. It was noted that the residual statistics check, although far from the mean values of the respective statistics Q

_{1}and Q

_{2}, were within the confidence level (CL) of 5%, so the selected semivariogram parameters cannot be rejected.

#### 3.8. Stockpile Volume Estimation

^{3}. The two blue lines show the traces of two sections of STK1.

## 4. Discussion

## 5. Conclusions

^{3}. The advantage of the Kriging method is that the uncertainty is also estimated. Based on the above methodology, new drillhole locations in areas of high Kriging variance can be proposed to minimise any uncertainty. It was noted that the most secure method would be to use topographic maps before placing the waste deposits, but this was not feasible due to time elapsed since the old open pit mine was abandoned.

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

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**Figure 1.**South view of the abandoned open pit North Mathiatis mine (Personal photo of Papaconstantinou).

**Figure 2.**Percentage presentation of UAV application in each mining process phase [14].

**Figure 3.**Display of factors, resulting in the massive sulfide ore deposits formation [41].

**Figure 13.**Final stockpile STK1 bottom surface (

**a**) before and (

**b**) after digitising from UAV data (blue line) boundary is applied.

**Figure 14.**Final stockpile STK1 of 56,000 m

^{3}with the traces of two sections in NS and WE direction.

Constant | Value | Constant | Value |
---|---|---|---|

${a}_{0}$ | 389.8 | ${a}_{3}$ | 1.423 × 10^{−3} |

${a}_{1}$ | 0.1194 | ${a}_{4}$ | 2.540 × 10^{−3} |

${a}_{2}$ | 0 | ${a}_{5}$ | 0 |

Model | Nugget | Sill | Range (m) | |
---|---|---|---|---|

Elevation (raw) | Gaussian | 2.6 | 58.4 | 80 |

Elevation (transformed) | Exponential | 0.06 | 6.8 | 41 |

Description | Min Value | Max Value |
---|---|---|

X | 531,900 | 532,020 |

Y | 3,870,400 | 3,870,580 |

Z | 0 | 1 |

Rotation | 0 | - |

Block Size (X, Y, Z) | 2 m × 2 m × 1 m | - |

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## Share and Cite

**MDPI and ACS Style**

Saratsis, G.; Xiroudakis, G.; Exadaktylos, G.; Papaconstantinou, A.; Lazos, I.
Use of UAV Images in 3D Modelling of Waste Material Stock-Piles in an Abandoned Mixed Sulphide Mine in Mathiatis—Cyprus. *Mining* **2023**, *3*, 79-95.
https://doi.org/10.3390/mining3010005

**AMA Style**

Saratsis G, Xiroudakis G, Exadaktylos G, Papaconstantinou A, Lazos I.
Use of UAV Images in 3D Modelling of Waste Material Stock-Piles in an Abandoned Mixed Sulphide Mine in Mathiatis—Cyprus. *Mining*. 2023; 3(1):79-95.
https://doi.org/10.3390/mining3010005

**Chicago/Turabian Style**

Saratsis, Georgios, George Xiroudakis, George Exadaktylos, Alexandros Papaconstantinou, and Ilias Lazos.
2023. "Use of UAV Images in 3D Modelling of Waste Material Stock-Piles in an Abandoned Mixed Sulphide Mine in Mathiatis—Cyprus" *Mining* 3, no. 1: 79-95.
https://doi.org/10.3390/mining3010005