Production of a Three-Dimensional Triangulated Irregular Network (3D TIN) for Al-Karkh University of Science, Baghdad- Iraq

Many satellite systems take cover images like QuickBird for terrain so that these images scan be used to construct 3D models likes Triangulated Irregular Network (TIN), and Digital Elevation Model (DEM). This paper presents a production of 3D TIN for Al-Karkh University of Science in Baghdad - Iraq using QuickBird image data with pixel resolution of 0.6 m. The recent generations of high-resolution satellite imaging systems open a new era of digital mapping and earth observation. It provides not only multi-spectral and high-resolution data but also the capability for stereo mapping. The result of this study is a production of 3D satellite images of the university by merging 1 m DEM with satellite image for ROI using ArcGIS package Version 10.3.

Zero Watermarking for the TIN DEM Data Based on the Edge Length

How to keep the fidelity of the digital elevation model (DEM) data is a crucial problem in the current watermarking research, as the watermarked DEM data need to preserve their accuracy. We proposed a zero watermarking method for the triangulated irregular network (TIN) DEM data. It takes full advantage of the characteristics of the edge length in the TIN DEM data. First, the radio of the edge lengths is quantified to the watermark index, and then the comparison of the edge lengths is quantified to the watermark bit. Finally, the watermark is constructed by combing the watermark bits according to the watermark indices with the help of the majority voting mechanism. In the method, the TIN DEM data are only used to construct the watermark, not to be embedded by the watermark. Therefore, the data quality is preserved to the greatest extent. Experiments verify the theoretical achievements of this method and demonstrate the method is lossless to the TIN DEM data. Simulation results also show that the method has good robustness on translation, rotation, scaling, and cropping attacks.

NOISE REDUCTION IN CONTOUR LINES AND SLOPE MAPS FROM MEDIUM/HIGH-DENSITY LIDAR DATA

The use of medium/high-density LIDAR (Light Detection And Ranging) data for land modelling and DTM (Digital TerrainModel) is becoming more widespread. This level of detail is difficult to achieve with other means or materials. However,the horizontal and vertical geometric accuracy of the LIDAR points obtained, although high, is not homogeneous.Horizontally you can reach precisions around 30-50 cm, while the vertical precision is rarely greater than 10-15 cm. Theresult of LIDAR flights, are clouds of points very close to each other (30-60 cm) with significant elevation variations, evenif the terrain is flat. And this makes the triangulated models TIN (Triangulated Irregular Network) obtained from such LIDARdata especially chaotic. Since contour lines are generated directly from such triangulated models, their appearance showsexcessive noise, with excessively broken and rapidly closed on themselves. Getting smoothed contour liness, withoutdecreasing accuracy, is a challenge for terrain model software. In addition, triangulated models obtained from LIDAR dataare the basis for future slope maps of the land. And for the same reason explained in the previous paragraph, these slopemaps generated from high or medium density LIDAR point clouds are especially heterogeneous. Achieving uniformity andgreater adjustment to reality by reducing the natural noise of LIDAR data is another added challenge. In this paper, theproblem of excessive noise from LIDAR data of high (around 8 points/m2) and medium density (around 2 points/m2) in thegeneration of contour lines and terrain slope maps is raised and solutions are proposed to reduce this noise. All this, in thearea of specific software for the management of TIN models and GIS (Geographic Information System) and adapting thealternatives proposed by these programmes.

UAV-Borne, LiDAR-Based Elevation Modelling: An Effective Tool for Improved Local Scale Urban Flood Risk Assessment

In this study we present the first findings of the potential utility of miniaturized Light and Detection Ranging (LiDAR) scanners mounted on Unmanned Aerial Vehicles (UAVs) for improving urban flood assessment at the local scale. This is done by generating high spatial resolution Digital Terrain Models (DTM) featuring buildings and urban microtopographic structures that can affect floodwater pathways (DTMbs). The accuracy and level of detail of the flooded areas simulated by a hydrologic screening model (Arc-Malstrøm), were vastly improved when DTMbs of 0.3 m resolution representing three urban sites surveyed by a UAV-LiDAR in Accra, Ghana, supplemented a commercially available 10 m resolution DTM covering the full catchment area of the region. The generation of DTMbs necessitated the effective classification of UAV-LiDAR point clouds using a morphological and a triangulated irregular network method for hilly and flat landscapes, respectively. The UAV-LiDAR enabled the identification of archways, boundary walls and bridges that were critical when predicting precise runoff courses that could not be projected using the DTM only. Variations in a stream’s geometry due to a one-year time gap between the satellite-based and UAV-LiDAR datasets were also observed. The application of the coarser DTM produced an overestimation of water flows equal to 15% for sloping terrain and up to 62.5% for flat areas when compared to the respective runoff simulated using the DTMbs. The application of UAV-LiDAR may enhance the effectiveness of urban planning by projecting precisely the location, extent and runoff of flooded areas in dynamic urban settings.

Caracterização geológica da porção centro-sul da Bacia Pernambuco com base na integração de modelo digital de elevação, dados magnetométricos e geológicos

Este trabalho descreve os principais aspectos geológicos, em escala de detalhe, observados para a porção centro-sul da Bacia Pernambuco, localizada em parte dos municípios de Ipojuca e Sirinhaém (PE). Seis unidades litoestratigráficas puderam ser individualizadas: o embasamento cristalino (rochas metamórficas intemperizadas), a Formação Cabo (conglomerados polimíticos), a Suíte Magmática Ipojuca (riolitos, basaltos e rochas piroclásticas), as formações Estiva (folhelhos verdes, calcíferos, com ausência de microfósseis) e Algodoais (argilitos e arenitos médios a finos, com fácies sedimentar vulcanogênica associada), e depósitos quaternários. Foram utilizadas ferramentas como o modelo digital de elevação (MDE) da Triangulated Irregular Network (TIN), derivado dos dados topográficos da Folha Sirinhaém (escala 1:25.000) e o mapa de amplitude do sinal analítico para auxiliar a cartografia geológica. Os lineamentos topográficos e magnéticos (trends NNW-ESE, NW-SE e NE-SW) correspondem à fase rifte. Esses lineamentos estão relacionados a falhas de borda (evento inicial) e, principalmente, à reativação dessas falhas, combinada à geração de novas falhas. Vinte e seis anomalias magnéticas positivas e circulares foram identificadas e podem refletir a assinatura de possíveis centros vulcânicos. Atentamos a ocorrência de dois possíveis grandes centros vulcânicos que se propagam em direção ao Platô de Pernambuco, sendo que um está localizado na porção leste da área (CV1), onde ocorre o maior volume de sedimentação quaternária, e o outro está inserido na porção sudoeste (CV2), e excede os limites da área estudada.

Recognizing Visibility Graphs of Triangulated Irregular Networks

A Triangulated Irregular Network (TIN) is a data structure that is usually used for representing and storing monotone geographic surfaces, approximately. In this representation, the surface is approximated by a set of triangular faces whose projection on the XY-plane is a triangulation. The visibility graph of a TIN is a graph whose vertices correspond to the vertices of the TIN and there is an edge between two vertices if their corresponding vertices on TIN see each other, i.e. the segment that connects these vertices completely lies above the TIN. Computing the visibility graph of a TIN and its properties have been considered thoroughly in the literature. In this paper, we consider this problem in reverse: Given a graph G, is there a TIN with the same visibility graph as G? We show that this problem is ∃ℝ-Complete.

TIN Surface and Radial Viewshed Determination Algorithm Parallelisation on Multiple Computing Machines

In this paper we have proposed a method of solving the computer graphic problem of creating a Triangulated Irregular Network (TIN) surface in large clouds in order to create viewsheds. The method is based on radial TIN surface and viewshed visualization task subdivision using multiple computing machines, which is intended to accelerate the process of generating the complete viewshed.

Base Point Split Algorithm for Generating Polygon Skeleton Lines on the Example of Lakes

This article presents the Base Point Split (BPSplit) algorithm to generate a complex polygon skeleton based on sets of vector data describing lakes and rivers. A key feature of the BPSplit algorithm is that it is dependent on base points representing the source or mouth of a river or a stream. The input values of base points determine the shape of the resulting skeleton of complex polygons. Various skeletons can be generated with the use of different base points. Base points are applied to divide complex polygon boundaries into segments. Segmentation supports the selection of triangulated irregular network (TIN) edges inside complex polygons. The midpoints of the selected TIN edges constitute a basis for generating a skeleton. The algorithm handles complex polygons with numerous holes, and it accounts for all holes. This article proposes a method for modifying a complex skeleton with numerous holes. In the discussed approach, skeleton edges that do not meet the preset criteria (e.g., that the skeleton is to be located between holes in the center of the polygon) are automatically removed. An algorithm for smoothing zigzag lines was proposed.

A Three-Dimensional Visualization Framework for Underground Geohazard Recognition on Urban Road-Facing GPR Data

The identification of underground geohazards is always a difficult issue in the field of underground public safety. This study proposes an interactive visualization framework for underground geohazard recognition on urban roads, which constructs a whole recognition workflow by incorporating data collection, preprocessing, modeling, rendering and analyzing. In this framework, two proposed sampling point selection methods have been adopted to enhance the interpolated accuracy for the Kriging algorithm based on ground penetrating radar (GPR) technology. An improved Kriging algorithm was put forward, which applies a particle swarm optimization (PSO) algorithm to optimize the Kriging parameters and adopts in parallel the Compute Unified Device Architecture (CUDA) to run the PSO algorithm on the GPU side in order to raise the interpolated efficiency. Furthermore, a layer-constrained triangulated irregular network algorithm was proposed to construct the 3D geohazard bodies and the space geometry method was used to compute their volume information. The study also presents an implementation system to demonstrate the application of the framework and its related algorithms. This system makes a significant contribution to the demonstration and understanding of underground geohazard recognition in a three-dimensional environment.