Undulating Terrain Research Articles

Time‐domain finite element method based on arbitrary quadrilateral meshes for two‐dimensional SHTE mode seismoelectric and electroseismic waves modelling

AbstractA time‐domain finite‐element method based on an arbitrary quadrilateral mesh is proposed to simulate two dimensional seismoelectric and electroseismic waves in SHTE mode. By decoupling the electrokinetic coupling equation, we can solve seismic waves and electromagnetic waves independently. For the simulation of seismic wavefield, we utilize a more compact second‐order unsplit perfectly matched layer that is easier to implement in finite‐element methods. Moreover, to avoid errors caused by the quasi‐static approximation, we directly solve the full‐wave electromagnetic equations when simulating the electromagnetic wavefield. Our computational domain is discretized using arbitrary quadrilateral meshes, which offers possibilities in handling undulating terrain and complex anomalies in the underground. To ensure computational accuracy, we utilized biquadratic interpolation as our finite‐element basis functions, which provides higher precision compared to bilinear interpolation. We validate our time‐domain finite‐element method by comparing its results with analytical solutions for a layered model. We also apply our algorithm to the modelling of an underground aquifer and a complex anomalous hydrocarbon reservoir under undulating terrain.

Geo-positioning Method of Optical Satellite Unconventional Stereo Imagery Based on Optimal Intersection

Generally, the classic three-dimensional (3D) geometric positioning of optical satellite imagery uses the least squares principle to calculate the coordinates of a ground point by minimizing the sum of the squares of the distances between two imaging rays, which requires the standard stereo data with good imaging geometric conditions. As for unconventional stereo images, the undesirable and ubiquitous weak intersection phenomena exist in data will lead to bad results or even calculation failures for the conventional method. By selecting the highest precision intersection point in block adjustment, a new method that can solve the 3D coordinates with higher accuracy and stability was proposed. Tests of two data sets covering different landscapes validated the effectiveness of the method. The results showed that the geo-positioning performance and robustness of the proposed method was better than that of the conventional method, and this advantage is even greater in areas with more undulating terrain and more images with weak convergence.

PERFORMANCE ASSESSMENT OF SPATIAL INTERPOLATIONS FOR TRAFFIC NOISE MAPPING ON UNDULATING AND LEVEL TERRAIN

Traffic noise mapping frequently employs Kriging, Inverse Distance Weighted (IDW), and Triangular Irregular Networks (TIN) spatial interpolations. This study uses the Henk de Kluijver noise model to evaluate the performance of spatial interpolations. Effective traffic noise mapping requires that noise observation points (Nops) be designed as 2 m grids. The upper and lower slopes function as noise barriers to reduce sound levels. Therefore, assessment of accuracy is essential for visualising noise levels in undulating and level terrain. In addition, this work gives an accurate comparison of traffic noise interpolation in undulating areas. The elements of spatial interpolations, such as the weighting factor, variogram, radius, and number of points influence the interpolation accuracy. The Kriging with a Gaussian variogram, where the radius is 5 m and the number of points is 12 demonstrates the highest level of precision. However, there is no direct relationship between accuracy validation and cross-validation. In cross-validation, however, the accuracy of the Gaussian variogram with a 7 m radius and 18 points is more accurate. In addition, this study demonstrates that Kriging is superior for extrapolating noise levels in undulating regions. Accurate visualising traffic noise levels requires a prior understanding of spatial interpolations.

Geographically induced and the spatially differentiated dimension of flood vulnerability in Greater Kumasi Metropolis, Ghana

ABSTRACT Over the past several years, the constant flooding events and their lethal consequences have reignited the debate on the need for vulnerability assessment of flood-prone communities in urban areas as a flood risk mitigation and adaptation measure. This article focuses on Ghana and uses remotely sensed high-resolution data, and community mapping to assess the flood vulnerability of 442 urban communities of the Greater Kumasi Metropolitan Area (GKMA). The Compound Topographic Index and the Shuttle Radar Topographic Mission were used systematically. The results showed that 43% of communities were found in low-risk areas, 30% were in medium-risk areas, and 27% were in high-risk areas. Flood intensity and frequencies were found to be dependent on location relative to slopes and undulating terrain. We argue that the identified flood hazard communities should guide policymakers in proffering specific and targeted interventions toward flood risk reduction and community resilience strategies

Shaded fraction and backtracking in single-axis trackers on rolling terrain

A generalized closed-form equation for the shaded collector fraction in solar arrays on rolling or undulating terrain is provided for single-axis tracking and fixed-tilt systems. The equation accounts for different rotation angles between the shaded and shading trackers, cross-axis slope between the two trackers, and offset between the collector plane and axis of rotation. The validity of the equation is demonstrated through comparison with numerical ray-tracing simulations and remaining minor sources of error are quantified. Additionally, a simple procedure to determine backtracking rotations for each row in an array installed on the rolling terrain (varying in the direction perpendicular to the tracker axes) is provided. The backtracking equation accounts for a desired shaded fraction (including complete shade avoidance) as well as an axis-collector offset. Test cases are provided to facilitate implementation of these equations.

Restoration of UAV-Based Backlit Images for Geological Mapping of a High-Steep Slope.

Unmanned aerial vehicle (UAV)-based geological mapping is significant for understanding the geological structure in the high-steep slopes, but the images obtained in these areas are inevitably influenced by the backlit effect because of the undulating terrain and the viewpoint change of the camera mounted on the UAV. To handle this concern, a novel backlit image restoration method is proposed that takes the real-world application into account and addresses the color distortion issue existing in backlit images captured in high-steep slope scenes. Specifically, there are two main steps in the proposed method, which consist of the backlit removal and the color and detail enhancement. The backlit removal first eliminates the backlit effect using the Retinex strategy, and then the color and detail enhancement step improves the image color and sharpness. The author designs extensive comparison experiments from multiple angles and applies the proposed method to different engineering applications. The experimental results show that the proposed method has potential compared to other main-stream methods both in qualitative visual effects and universal quantitative evaluation metrics. The backlit images processed by the proposed method are significantly improved by the process of feature key point matching, which is very conducive to the fine construction of 3D geological models of the high-steep slope.

Wind erosion and transport on planetesimals

We consider the possibility that aeolian (wind blown) processes occur on small, 1 to 100 km diameter, planetesimals when they were embedded in the protosolar nebula. Drag from a headwind within a protostellar disk is sufficiently large to loft cm and smaller sized particles off the surface of a 10 km diameter asteroid in the inner solar system (at a few AU), and micron sized particles off the surface of a 10 km diameter object in the Transneptunian region. The headwind is sufficiently strong to overcome surface cohesion in the inner solar system, but not in the outer solar system. However, in the outer solar system, surface particles can be redistributed or escape due to impacts from particles that are in the protosolar disk’s wind. Based on scaling crater ejecta, we estimate that impacts from particles in the headwind will lead to erosion of mass rather than accretion for planetesimals below about 6 km in diameter. The erosion limit is independent of material strength but proportional to the wind velocity. We explore the sensitivity of splash particle trajectories to particle size, headwind velocity and Reynolds number. Winds from a protostellar disk could account for Kuiper Belt Object (486958) Arrokoth’s smooth undulating terrain but only during an epoch of high particle flux and low wind velocity. These conditions could have been present during and just after coalescence of Arrokoth’s building blocks.

The ES-GNF method of unstructured tetrahedral mesh for fast inversion of gravity and magnetic data with undulating terrain

The ES-GNF method of unstructured tetrahedral mesh for fast inversion of gravity and magnetic data with undulating terrain

THE SCALE OF RECREATIONAL ASSESSMENT OF SUBURBAN FORESTS IN LVIV (ON THE EXAMPLE OF BRIUKHOVYCHI FORESTRY)

Using the comprehensive assessment proposed by the authors of the article, a study of recreational and health forests in Lviv was conducted on the example of the Bryukhovychi forestry. The presented methodology combines 29 indicators, which are grouped into blocks: attractiveness, comfort, and sustainability. Each of the indicators is evaluated on a 5-point scale (from 0 to 4). The methodology combines environmental, biological and anthropogenic factors. The calculated average score of the integrated assessment for the three blocks of indicators for the plantations of the Bryukhovychi forestry is 2.7, which indicates an average degree of recreational potential. The average score for the attractiveness block indicators is 3.0, which indicates a high level of landscape aesthetics. The studied stands are complex and multi-tiered in their composition. Among the dominant species, the following should be noted: Pinus sylvestris L., Fagus sylvatica L., Fraxinus excelsior L., Acer platanoides L., Tilia cordata Mill., Betula pendula Roth., Quercus robur L., Q. rubra L., Alnus glutinosa (L.) Gaerth., Carpinus betulus L., Larix decidua Mill., Ulmus glabra Huds. The tree stands of the Bryukhovychi forestry belong to the category of ripening and mature, such plantations are rated with the highest score due to their attractiveness and decorative appearance The average score of the studied quarters for the comfort block indicators is 2.7, which indicates an average indicator that reflects the level of improvement and the degree of comfort of recreationists. Most of the recreational and health forests of the Bryukhovychi forestry have hilly and undulating terrain, and in 60-61 blocks, ravine and gully terrain, which is quite attractive but poorly suited for recreational activities. The average assessment of the comfort of recreational and health forests by the indicator "relief" is 2 points and is characterized as moderately suitable for active recreation According to the indicators of the sustainability block, the average score is similar to the comfort block, namely 2.7. The comfort of stay is significantly affected by the noise factor, the condition of the road and trail network, and the presence of annoying insects. In the blocks that are at the III-IV stage, the stability of the lower forest components is estimated at 1-2 points, and the success of natural regeneration is insufficient. In areas at the I-II stage of recreational degradation, the average sustainability score is 3.7, which is quite high and indicates a low level of human intervention. The condition of the undergrowth is characterized as "good" and natural regeneration as "reliable". This methodology of integrated assessment is dynamic because it includes variable parameters that depend on the time of day and season and is suitable for use throughout the calendar year.

Abundant resources compensate for the uneven distribution of ungulates in desert grassland.

Strategically managing livestock grazing in arid regions optimizes land use and reduces the damage caused by overgrazing. Controlled grazing preserves the grassland ecosystem and fosters sustainability despite resource limitations. However, uneven resource distribution can lead to diverse grazing patterns and land degradation, particularly in undulating terrains. In this study, we developed a herbivore foraging algorithm based on a resource selection function model to analyze foraging distribution patterns, predict the probability of foraging, and identify the determinants of foraging probability in cattle. The study area was a complex desert landscape encompassing dunes and interdunes. Data on cattle movements and resource distribution were collected and analyzed to model and predict foraging behavior. Our findings revealed that cattle prefer areas with abundant vegetation in proximity to water sources and avoid higher elevations. However, abundant resource availability mitigated these impacts and enhanced the role of water points, particularly during late grazing periods. The analysis showed that available resources primarily determine foraging distribution patterns and lessen the effects of landforms and water distance on patch foraging. The results suggest that thoughtful water source placement and the subdivision of pastures into areas with varied terrain are crucial for sustainable grazing management. By strategically managing these factors, land degradation can be minimized, and the ecological balance of grassland ecosystems can be maintained. Further research is needed to refine the model and explore its applicability in other arid regions.

Raw Data Simulation under Undulating Terrain for Bistatic SAR with Arbitrary Configuration

Raw Data Simulation under Undulating Terrain for Bistatic SAR with Arbitrary Configuration

Detection and mapping of supraglacial lakes on East Antarctic margin using Landsat 8 OLI during 2014–2023

Using an optical band index generated from Landsat 8 OLI data, an inventory of Antarctic supraglacial lakes (size >0.01 km2) during 2014–2023 is presented. Shaded snow, cloud and rock shadow were removed by using a band-based filter. Over the north Antarctica, we identified 639 lakes covering an area of 520.79 km2, 1025 lakes covering 272.82 km2 over the East Antarctica, and 1045 lakes covering 93 km2 over the Transantarctic Mountains. The influence of air temperature, 10-m zonal/meridional wind components and climate indices on surface melt were investigated. Over the Dronning Maud Land, air temperature promoted melt, while Föhn and katabatic winds warmed adiabatically along the leeward side of the elevated features and initiated melt in south Antarctica. Nearly all areas have exhibited a decrease in melt over the past few years, and the number of melt cases dropped after 2020. Negative SAM index favoured melt over the Dronning Maud Land. This study identified new SGLs, which will be a benchmark for further studies. The undulating terrain posed a difficulty for collecting and interpreting satellite data, which should be addressed using advanced technologies and algorithms.

Omnidirectional Battery Electric Vehicle for Use in Oil Palm Plantation

Concerns on the low labour shortage and the need to reduce greenhouse gas (GHG) generation prompted the industrial player to increase mechanisationduring operation and adopting low carbon footprint mobile platforms. In this paper, a design and analysis study was conducted and reported on a conceptual battery electric vehicle (BEV) for use in the oil palm plantations. With a maximum operating road speed of 30km/hr and harvesting load of 320kg, the BEV will require a minimum operational power of 44.5kW. In accommodating the soggy ground with the demand to navigate narrow and undulating terrains, the proposed BEV was designed to be equipped with an omnidirectional functionality with continuous track, without the use of conventional wheels. Major components arrangement and design for the omnidirectional mechanism are presented in this paper. This preliminary work will also serve as the foundation towards refining the BEV design, especially on the vehicle functionality and manoeuvrability in the plantation sites. Further recommendations are also outlined that will focus on validating the conceptual design and analysis on the total energy generation and consumption of the BEV.

Influence of Topography on UAV LiDAR-Based LAI Estimation in Subtropical Mountainous Secondary Broadleaf Forests

The leaf area index (LAI) serves as a crucial metric in quantifying the structure and density of vegetation canopies, playing an instrumental role in determining vegetation productivity, nutrient and water utilization, and carbon balance dynamics. In subtropical montane forests, the pronounced spatial heterogeneity combined with undulating terrain introduces significant challenges for the optical remote sensing inversion accuracy of LAI, thereby complicating the process of ground validation data collection. The emergence of UAV LiDAR offers an innovative monitoring methodology for canopy LAI inversion in these terrains. This study assesses the implications of altitudinal variations on the attributes of UAV LiDAR point clouds, such as point density, beam footprint, and off-nadir scan angle, and their subsequent ramifications for LAI estimation accuracy. Our findings underscore that with increased altitude, both the average off-nadir scan angle and point density exhibit an ascending trend, while the beam footprint showcases a distinct negative correlation, with a correlation coefficient (R) reaching 0.7. In contrast to parallel flight paths, LAI estimates derived from intersecting flight paths demonstrate superior precision, denoted by R2 = 0.70, RMSE = 0.75, and bias = 0.42. Notably, LAI estimation discrepancies intensify from upper slope positions to middle positions and further to lower ones, amplifying with the steepness of the gradient. Alterations in point cloud attributes induced by the terrain, particularly the off-nadir scan angle and beam footprint, emerge as critical influencers on the precision of LAI estimations. Strategies encompassing refined flight path intervals or multi-directional point cloud data acquisition are proposed to bolster the accuracy of canopy structural parameter estimations in montane landscapes.

HIGH-RESOLUTION MAPPING OF FORESTED HILLS USING REAL-TIME UAV TERRAIN FOLLOWING

Abstract. This study presents a novel method for high-altitude terrain following photogrammetric mapping using Unmanned Aerial Vehicles (UAVs) that adapt their height to the terrain's morphology. Traditional grid missions in UAV mapping surveys use nadir photographs to cover an area of interest which is taken from a fixed height from the datum.Many times this leads to difficulties in flight mission and processing when hilly/undulated terrain is under consideration. The proposed solution addresses this by adjusting the UAV's flying height based on real-time terrain information gathered by a range detection sensor. This paper tests the proposed method in a hilly area in the Himalayas, capturing high-resolution images and processing them using UAV-based photogrammetry software. The pre-acquired terrain information ensures safe separation from obstacles and enables trajectory generation at lower altitudes when planning initial flights. The experimental results validate the effectiveness of the proposed method and highlight its potential for generating high-resolution photogrammetric products applicable to various UAV mapping tasks and monitoring scenarios. Overall, this research contributes to advancing the field of UAV mapping by providing a practical and effective solution for UAV based surveys in hilly and undulated terrains. The findings of this study have significant implications for various applications, including land surveying, environmental monitoring, landslide mapping and other scenarios that require detailed and accurate data acquisition from UAVs.

Characteristics of cloud-to-ground lightning (CG) and differences between +CG and −CG strokes in China regarding the China National Lightning Detection Network

Abstract. A lightning location system consisting of multiple ground-based stations is an effective means of lightning observation. The dataset from CNLDN (China National Lightning Detection Network) in 2016–2022 is employed to analyze the temporal and spatial lightning distributions and the differences between +CG (positive cloud-to-ground lightning) and −CG (negative cloud-to-ground lightning) strokes in China. On the annual scale, lightning activity is most prevalent during the summer months (June, July, and August), accounting for 72.6 % of the year. Spring sees more lightning than autumn, and winter has only a small amount in southeastern coastal areas. During the day, the frequency of lightning peaks at 15:00–17:00 CST (China standard time) and is lowest at 8:00–10:00 CST. For the period with high CG stroke frequency (summer of a year or afternoon of a day), the proportion of +CG strokes and the discharge peak current are relatively small. Winter in a year and morning or midnight in a day correspond to a greater +CG stroke proportion and discharge current. Spatially, low latitudes, undulating terrain, the seaside, and humid surfaces are favorable factors for lightning occurrence. Thus, the southeast coastland has the largest lightning stroke density, while the northwest deserts and basins and the western and northern Tibetan Plateau, with altitudes over 6000 m, have almost no lightning. The proportion of +CG strokes and the peak current are low in the southern region with high density but diverse in other regions. The Tibetan Plateau causes the diversity of lightning activity in China and lays the foundation for studying the impact of surface elevation on lightning. Results indicate that the +CG stroke proportion on the eastern and southern Tibetan Plateau is up to 15 %, larger than the plain regions. The peak current of −CG strokes is positively correlated with altitude, but +CG strokes show a negative correlation, resulting in a large difference in peak current between +CG and −CG on the plain and a small difference on the plateau.

Numerical Modeling of Anisotropic Magnetic Field for High Susceptibility in Undulating Topography

Most minerals with high magnetism have anisotropic characteristics, and the magnetic field distribution will be affected by topography. Based on the numerical modeling of magnetic field of anisotropic ferromagnetic body, this paper introduces the undulating topographic surface, sets up multiple horizontal planes with different depths between the highest point and the lowest point of the undulating terrain, calculates the magnetic field of these horizontal planes, and finally obtains the distribution of magnetic anomaly field on undulating topographic surface through interpolation. The correctness of undulating topography calculation is verified by comparison with the analytical solution. It is of great significance for inversion imaging of strong magnetic bodies in undulating topography.

A new frontier of archaeological dark earth at the northern Amazonia headwaters of Roraima state: Soil attributes and landscape interplays

Despite the existence of various studies on Archaeological Dark Earth - ADE, there is still a very large gap concerning the Amazon region, with many areas remaining unexplored scientifically. The aim of this study, therefore, was to characterize and classify areas of Archaeological Dark Earth located on rural properties and in one riverside community in the southern mesoregion of the state of Roraima. At these locations, trenches were dug in a total of 13 areas, and the profiles morphologically characterized and sampled for soil classification and Carbon-14 dating. The areas were georeferenced and measured, and the history of land use was described, together with the predominant vegetation in the region. The following physical analyses were carried out: texture and bulk density. The chemical analysis consisted of pH in water and KCl, exchangeable cations, exchangeable Al, available P, titratable acidity (H + Al), total N and organic matter. To produce the maps, computational processing was used in a Geographic Information System - GIS, employing geoprocessing tools with the aid of the ArcGIS v10.6 software; the attributes prepared from SRTM images were drainage network and terrain. Using the Brazilian System of Soil Classification (SiBCS), the profiles were classified as: Argissolos Amarelos, Cambissolo Háplico, Latossolos Amarelos, Argissolo Vermelho Amarelo, and Nitossolo Vermelho. It is suggested that the anthropogenic subgroup be included in the SiBCS. With the exception of 3 horizons, the anthropogenic horizon of each of the profiles sampled in the region has a eutrophic character, with ages that range from 1120 to 1864 years before present (YBP). Each of the areas of ADE is associated with a drainage network ranging from a small creek, approximately 6m wide, to a fast-flowing river, such as the Branco River, which is over 1,700m wide. The 13 areas are located in places away from the flood area that show little variation in relief, with a predominance of flat to gently undulating terrain.

Evaluation of Slope Correction Methods to Improve Surface Elevation Change Estimation over Antarctic Ice Sheet using SARAL/AltiKa

Antarctic Ice Sheet (AIS) surface elevation change plays a crucial role in understanding the ice sheet mass balance. The present study focuses on improving AIS surface elevation estimations by incorporating slope correction methods called Direct Method (DM) using SARAL/AltiKa 40 Hz geophysical data record for 2013 (Exact Repeat Mission) and 2020 (Drifting Phase) with terrain slope ranges from 0° to 0.85°. The NASA's Ice, Cloud, and land Elevation Satellite (ICESat) Digital Elevation Model (DEM) has been utilized as a priori topography model to retrieve slope of the AIS terrain. While comparing the two direct methods (DM1 & DM2) based slope corrected elevations with Operation Ice Bridge (OIB) elevation data of November 2013, the RMSE resulted in 0.35 and 0.37 m and biases of the order of 0.26 m and 0.28 m for DM1 and DM2 respectively. Moreover, comparison with ICESat DEM showed the RMSE of the order of 1.81 and 2.09 m, and biases of the order of 0.95 and 0.99 m for DM1 and DM2, respectively. It has been observed that DM1 is the most suitable method for correcting terrain slope with the lowest RMSE and bias. Moreover, the slope induced error correction methods show utmost importance in estimating accurate elevation, especially over undulating terrain of AIS.

Showcasing Incredible India Through Swachh Bharat Abhiyan: Swachh Smarak, Swachh Pakwan And Swachh Paryatan

India is a nation renowned for its rich and storied history, boasting one of the world's oldest and most advanced civilizations. Its diverse landscape features perennial rivers, undulating terrain, verdant mountains, evergreen rainforests, and stunning beaches in Goa, as well as the breathtaking backwaters of Kerala and the snow-capped paradise of North India. Cleanliness is crucial for travellers when selecting a destination as it greatly affects their experience and perception of the place. In order to enhance the reputation of popular tourist destinations in India as clean and secure places, a range of measures have been implemented. One of the key initiatives taken by the Indian government to enhance cleanliness in the country is the Swachh Bharat Abhiyan campaign. Swachh Bharat Abhiyan is really a magical tool if used efficiently; it will change the image of India on the world map and will positively increase the number of tourists visiting the country. Swachh Bharat Abhiyan also helps in achieving the motto of ‘Incredible India’ and ‘Atithi Devo Bhava’ programmes. Thus in this present paper, the researchers focus on the importance of Clean India Campaign for promoting Indian Tourism and also explore the various initiatives under Swachh Bharat Abhiyan: Swachh Bharat – Swachh Smarak, Swachh Bharat – Swachh Pakwan and Swachh Bharat – Swachh Paryatan as the backdrop of Incredible India.