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3D LoD3 Modeling of High Building Using Terrestrial Laser Scanning and Unmanned Aerial Vehicle: A Case Study in Halong City, Vietnam

Le Thi Thu Ha, Nguyen Quoc Long

Inżynieria Mineralna

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2023

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no. 2, vol. 1

303--310

EN

3D urban building models play an important role in the association, convergence and integration of economic and social urban data. 3D building reconstruction can be done from both the lidar and image-based point clouds, however, the lidar point clouds has dominated the research giving the 3D buildings reconstruction from aerial images point clouds less attention. The UAV images can be acquired at low cost, the workflow can be automated with minimal technical knowhow limitation. This promotes the necessity to understand and question to what extent the 3D buildings from UAV point clouds are complete and correct from data processing to parameter settings. This study focuses on proposing a process for building 3D geospatial data for a smart city using geospatial data collected by UAV and Terrestrial Laser Scanner. The experimental results have produced 3D geospatial data of high building in LoD3, with the root mean square error of the received test points mΔx=3.8 cm, mΔy=3.1 cm, and mΔH=7.5 cm.

2

The Impact of Coal Exploitation on Tidal Flat Changes, an Investigation Using Remote Sensing Data in Vietnam

Pham Thi Lan, Tong Si Son, Le Thi Thu Ha, Le Thi Le, Hoang Huu Duc

Inżynieria Mineralna

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2021

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no. 2

521--532

EN

Tidal flat plays a crucial role in socio-economic development and ecological environment. Tidal flats in Ha Long-Cam Pha in Vietnam are impacted by human activities, especially coal mining activities. Using remote sensing data is able to detect, extract, and monitor the changes of tidal flats and exploited coal mine area with multi-temporal, in various scales, and for a large coverage. This study aims to investigate the impact of coal mining activities on the changes of tidal flats using remote sensing in Cam Pha, Ha Long, one of the biggest coal basins in Vietnam. Digital Elevation Models (DEMs) of tidal flats constructed by Landsat satellite images acquired in years 1989, 2001, and 2014 are compared to determine the volume changes. Besides, coal mining activities including coal production, waste rock dump area, and the expansion of open coal mine during the period 1989-2014 are investigated using correspondent Landsat images and the reports from the coal mine companies in the study area. Sediment samples in tidal flats are analyzed to determine the origin of the sediments. As the results, organic matter in the tidal flats is dominant with the concentration of 459 g/kg to 607 g/kg, which is evidence for the impact of coal exploitation on the coastal environment. In addition, the relationship between coal mine activities and tidal flat variation is well observed in this study.

3

Assessing Impacts of Mining Activities on Land Use/Land Cover Change Using Remote Sensing and GIS Techniques: A Case Study in Campha City, Vietnam

Le Thi Thu Ha

Inżynieria Mineralna

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2021

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no. 2

467--477

EN

Coal is one of the most mining commodities to date, especially to supply both national and international energy needs. Coal mining activities that are not well managed will have an impact on the occurrence of environmental damage. The present study was undertaken to analyze the process of humaninduced landscape transformation in the coal mines affected areas of Cam Pha, northeast Vietnam by interpreting temporal remote sensing data and using Geographic Information System. This experiment revealed that most of the study area was dominated by forest in all the time sequence period. The forest cover has decreased about 21.3%, meanwhile having nine fold increase in mining area from 1990 to 2020. The forest area lost during the study period was 7983.45 ha due to land cover conversion into mining area. The mining activities were also detrimental to the bare land and water body cover. The results of this study are expected to be used to support government efforts and mining managers in post-mining coal activities.

4

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

Le Van Canh, Cao Xuan Cuong, Nguyen Quoc Long, Le Thi Thu Ha, Tran Tuan-Anh, Bui Xuan‑Nam

Inżynieria Mineralna

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2020

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no. 2, vol. 1

65--74

EN

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.

PL

Tereny kopalni odkrywkowych w Wietnamie są często pozbawione roślinności o silnie zróżnicowanej morfologii utworzone w wyniku eksploatacji górniczej. Tradycyjne prace geodezyjne w kopalniach odkrywkowych są czasochłonne. W artykule, przedstawiono wyniki badania dotyczącego procesu technologicznego generowania 3D modeli i ortofotomapy na podstawie danych pozyskanych z pokładu bezzałogowej platformy UAV typu DJI Phantom 4RTK. Współcześnie bezzałogowe statki powierzchne (BSP) stanowią̨ dobrze rozwiniętą gałąź́ lotnictwa, która umożliwia pozyskiwanie danych z pułapu od kilku do kilkuset metrów. Własność́ ta stwarza nowe możliwości zastosowanie UAV w w kopalniach odkrywkowych. Omawiano metodę połączenia techniki fotogrametrii „Struktury z ruchu” (SfM) i fotogrametrii UAV, która jest szeroko stosowana w pomiarach topograficznych. Podczas gdy ważna rola naziemnych punktów kontrolnych (GCP) w dokładności cyfrowego modelu powierzchni (DSM) generowanego na podstawie obrazów uzyskanych przez „tradycyjne” UAV (a nie drony z obsługą RTK) została udowodniona w wielu poprzednich badaniach, nie jest to jasne w przypadek dronów obsługujących RTK, zwłaszcza na skomplikowanym terenie w odkrywkowych kopalniach węgla. W tym badaniu eksperymentalnie zbadano wpływ GCP pod względem jego liczby i rozmieszczenia na dokładność generowania DSM na podstawie obrazów uzyskanych przez drony z obsługą RTK w odkrywkowych kopalniach węgla. Dodatkowo, tryb Post Processing Kinematic (PPK) został uruchomiony na polu testowym na tej samej wysokości lotu. Generowanie DSM przeprowadzono z kilkoma konfiguracjami sterowania blokami: tylko PPK, PPK z jednym GCP i PPK z dwoma GCP. Zbadano również kilka pozycji GCP, aby przetestować optymalne lokalizacje do umieszczania GCP w celu uzyskania dokładnych DSM. Wyniki pokazują, że podana przez PPK dokładność pozioma i pionowa wyniosła odpowiednio 9,3 i 84,4 cm. Jednak po dodaniu co najmniej jednego GCP dokładność została znacznie poprawiona zarówno w komponentach poziomych, jak i pionowych, przy RMSE dla XY i Z w zakresie od 3,8 do 9,8 cm (z jednym GCP) i od 3,0 do 5,7 cm (z dwoma GCP), odpowiednio. Ponadto GCP umieszczone w głębokich obszarach kopalni odkrywkowej mogą zapewnić dokładność w granicach centymetrowych (cm).