Terrain Contours Research Articles

A Multi-Scale Fusion Strategy for Side Scan Sonar Image Correction to Improve Low Contrast and Noise Interference

Side scan sonar images have great application prospects in underwater surveys, target detection, and engineering activities. However, the acquired sonar images exhibit low illumination, scattered noise, distorted outlines, and unclear edge textures due to the complicated undersea environment and intrinsic device flaws. Hence, this paper proposes a multi-scale fusion strategy for side scan sonar (SSS) image correction to improve the low contrast and noise interference. Initially, an SSS image was decomposed into low and high frequency sub-bands via the non-subsampled shearlet transform (NSST). Then, modified multi-scale retinex (MMSR) was employed to enhance the contrast of the low frequency sub-band. Next, sparse dictionary learning (SDL) was utilized to eliminate high frequency noise. Finally, the process of NSST reconstruction was completed by fusing the emerging low and high frequency sub-band images to generate a new sonar image. The experimental results demonstrate that the target features, underwater terrain, and edge contours could be clearly displayed in the image corrected by the multi-scale fusion strategy when compared to eight correction techniques: BPDHE, MSRCR, NPE, ALTM, LIME, FE, WT, and TVRLRA. Effective control was achieved over the speckle noise of the sonar image. Furthermore, the AG, STD, and E values illustrated the delicacy and contrast of the corrected images processed by the proposed strategy. The PSNR value revealed that the proposed strategy outperformed the advanced TVRLRA technology in terms of filtering performance by at least 8.8%. It can provide sonar imagery that is appropriate for various circumstances.

Геоінформаційні системи для створення геодезичної основи і побудови генеральних планів населених пунктів

The use of geoinformation systems in conducting geodetic activity is a modern method of geodetic production. The development of a master plan for the territory of a settlement begins with the implementation of geodetic measurement works and the construction of a geodetic cartographic base. Geodetic measuring works are now carried out with modern geodetic devices that provide high accuracy of results, which meets the modern requirements of conducting geodetic activities in our country. With the help of modern software, they process the results of geodetic measurements and further build cartographic material. The application of Remote Sensing of the Earth data makes it possible to spatially link to terrain contours and determine the scope of geodetic measurement works for the further development of general plans of settlements. Modern requirements for the development of urban planning and land management documentation require the use of the latest devices and technologies. The use of high-precision electronic tacheometers and satellite radio navigation systems makes it possible to perform geodetic measurement work quickly and qualitatively in compliance with modern requirements for them. The use of GIS technologies, remote sensing of the Earth and modern programming makes it possible to create cartographic products in digital and paper form. The main purpose of using GIS technologies and DZZ data is to quickly identify the territory of the geodetic survey, find the points of the State Geodetic Network according to the data of the geoportal of Ukraine as a GIS technology system for linking to the starting points and obtaining initial information about them. The use of information layers of the Public Cadastral Map can help to find the source information about the territories of geodetic measurements as quickly as po The use of geodetic software enables the processing of the results of geodetic measurements and the construction of maps, plans, schemes and other cartographic products in symbols of the appropriate scale quickly and accurately. The construction of such cartographic materials serves as a geodetic basis for the development of general plans for the settlement. Our study was the territory of the village of Ivano-Shychyne, Bogodukhiv district, Kharkiv region, which belongs to the forest-steppe zone of Ukraine. To develop a master plan for the village of Ivano-Shychyne with complex relief conditions and the development of degradation processes of the soil cover had to perform a geodetic cartographic basis in digital form. And only after that, develop a master plan, since the old cartographic materials have long since lost their weight. The whole situation has changed a long time ago, new building blocks have appeared, the street and road network has developed. To compare the situation, we used the data of the DZZ, where we found significant changes, which were reflected on the constructed cartographic materials, which simplifies the solution to the problem.

Method for continuous multiscale representation of terrain contours using T‐spline technique

AbstractContours are the main graphical element for characterizing three‐dimensional terrain on a topographic map. Continuous multiscale representation of contours is crucial to meet users' needs for detailed information between fixed‐scale contours. Wherein shape of the contour should ideally progressively change as the scale continuously changes. However, the lack of a bridge between scale and shape deformation degrees is an obstacle in obtaining continuous multiscale contours. A novel method for continuous multiscale representation of contour based on T‐spline (CMRTS) is proposed. Multiscale contours are generated through interpolation of the T‐spline and constraint of the relationship between scale and shape similarity. First, a T‐spline surface is established using two fixed‐scale contours. Second, the T‐spline surface intersects a set of horizontal planes with gradual heights to generate intersecting lines. Finally, the quantitative relationship between the scale and shape similarity is determined to align each intersecting line with the corresponding scale and achieve continuous multiscale contours. A case study in Chongqing, China implements and evaluates the proposed method. Results indicate that shape changes of contours generated by CMRTS are more natural and progressive than those by two typical methods. Our method shows high potential and practicability for mapping continuous multiscale contours for real‐world terrain applications.

A Global Continuous Multi-Scale Terrain Contour Simplification Method Based on the Level Set

Multi-scale spatial representation has been widely used in geographic information and online mapping systems. Terrain contour, which provides a reference for understanding and monitoring the Earth’s surface, is an important data category. For the multi-scale representation of contour lines, simplification is a fundamental step in providing different levels of detail for linear features. However, achieving a global continuous multi-scale simplification of contours remains a challenge. Therefore, based on the concept of level set, a novel contour simplification method labeled the continuous changing surface model (CCSM) was proposed in this paper. The CCSM was built by using a non-uniform rational B-spline constrained with characteristics and was then intersected with a set of horizontal planes with progressive height values. The generated intersection lines are considered continuous multi-scale simplified contours. Experiments were conducted on a 1:50,000 real contour dataset to verify the effectiveness of CCSM. Results showed that the changes in the shape of the simplified contours generated by CCSM are more natural and progressive than those generated by two other significant simplification methods. CCSM can also effectively balance local and global structures and has potential applications in obtaining a continuous multi-scale representation of terrain contours.

Review of snake robots in constrained environments

Snake robots have advantages of terrain adaptability over wheeled mobile robots and traditional articulated robot arms because of their limbless thin body structure and high flexibility. They have extensive applications in tasks such as rescue, disaster recovery, inspection and minimally invasive surgery. Current research on snake robots is mainly focused on snake-like locomotion and the embodiment of these motion gaits for different applications. Modular structure and real-time control algorithms are two key aspects for snake robots operating in constrained environments. This review will attempt to address both. First, a review on the snake motion and the body structure is provided, which outlines the biological foundation of all snake robots. This is followed by the mechanical structure of snake robots, especially the structure of elemental snake modules. Finally, control algorithms for variant terrain contours and obstacle avoidance are discussed. The review also outlines emerging application areas and potential future directions of snake robots.

Remote Sensing Monitoring of the Bottom Topography in a Shallow Reservoir and the Spatiotemporal Changes of Submerged Aquatic Vegetation Under Water Depth Fluctuations

Monitoring the growth and distribution of submerged aquatic vegetation (SAV) is crucial to the protection and restoration of the ecosystem of inland reservoirs. Considering the high sensitivity of SAV to water depth fluctuations in Guanting Reservoir, China, in this study, we realized the reconstruction of bottom topography by combining changing water level with a long time series remote sensing technology and explored the spatiotemporal succession law of SAV by analyzing the effect of water depth on the spatiotemporal distribution of SAV. Results of water depth spatial distribution in Guanting Reservoir were obtained by using water and land boundary lines to construct underwater terrain contours. The accuracy of estimated water depth data from remote sensing images was verified with measured water depth data, and the average relative error of water depth estimation results was about 0.25 m. The experimental results show that (1) the SWIR bands of Landsat images could avoid the interference of aquatic vegetation and realize the separation of land and water; and (2) after separating water area from land, an SWIR1_NIR index was used to effectively map SAV distribution in the reservoir. The results also indicate that the distribution of SAV in the reservoir is suitable for the water depth range of 0−2 m. Water depth fluctuations cause changes in the spatial distribution of suitable water depth. It is the main reason for the change of SAV distribution area in the reservoir during the past 20 years.

A comparative study of modern UAV platform for topographic mapping

Unmanned Aerial Vehicle (UAV) has emerged as latest and widely used surveying equipment worldwide for topographic mapping. There has been a growing increased in number and type of UAV platform for image capturing. This research aims at analysing the effects of UAV platform on image quality and further on its output products like orthomosaic, Digital Surface Model (DSM), Digital Terrain Model (DTM) and contours. For this study, part of the main campus area of Universiti Teknologi Malaysia has been selected, covering around 0.52 sq. km. Two different types of UAV surveying platforms used are eBee classic fixed wing (eBee) and DJI Phantom 4 Advanced (P4) multirotor quadcopter. Surveying through both the platforms conducted by flying both UAV’s on 300 meters height, with 75%, front and 75% side overlap. Both have almost identical camera parameters so as ground sampling distance (GSD). 8 ground control points (GCPs) for image processing and 15 checkpoints (CP) were used for accuracy assessment. Final processing is done by using Pix4D software. The results show that all the UAV output were successfully produced for both type of UAVs. In general, the output of P4 UAV is superior to eBee UAV. As conclusion, the P4 UAV is more practical to be employed for topographic map of small area coverage as shown in this study due to capability of producing accurate result, portable, low cost and offer other advantages.

Numerical Simulation of the Water Surface Movement with Macroscopic Particles on Movable Beds

In this paper, on the basis of the three-dimensional Navier-Stokes equation, an incompressible fluid flow has been studied numerically when a dam is broken. In order to simulate this problem, a modification of the standard VOF model was carried out and a combination of Newtonian and non-Newtonian models was used. The flow effect on the transport of solid particles and mobile sediment has been shown. Several experiments were simulated to evaluate the computational model. All the obtained numerical results showed good agreement with the experimental data and the results of other authors. The effect of the mixture, which consists of solid particles and mobile deposits on the fluid flow, was studied in detail. The results of the flow behavior and transfer of solid particles at different heights of the moving layer were also shown. According to the numerical results analysis, the effect of dam destruction can be divided into the stage of high-speed impact and the flood stage. The first can cause damage due to instant exposure, and the second can cause damage due to stagnation. The simulation analysis of this work can be useful in hydropower to prevent breakthroughs of reservoirs with real terrain and real coastal contours. This investigation improves the understanding of bed topography with the solid particles effects of downstream dams impact based on simulation analysis.

Energy-Efficient Anti-Flocking Control for Mobile Sensor Networks on Uneven Terrains

Anti-flocking controlled mobile sensor networks (MSNs) have demonstrated impressive dynamic area coverage performances. Even though MSNs are often utilized in outdoor environments that consist of uneven terrains, existing anti-flocking control protocols are designed for flat terrain navigation. Thus, they tend to maneuver mobile sensory units along shortest paths between navigation goals in an area of interest. Even though navigating along shortest paths can be both time- and energy-efficient on flat terrains, such motions can often result in excessive energy consumptions on uneven terrains. This brief proposes an energy-efficient anti-flocking control protocol for MSNs based on a terrain adaptation force and a navigation goal selection method. The proposed control protocol encourages mobile sensory units to follow terrain contours whenever feasible. Test results show that the proposed control protocol is a promising energy-efficient solution for MSNs operating on uneven terrains.

Water Bodies Extraction and Terrain Analysis for Finding Critical Water Scarcity Locations using Elevation Data

The present study is aimed to create some new methods for extraction of water bodies (Rivers and Reservoirs) and analyze the land formation of terrain using elevation data. The digital elevation models (DEM) are used to extract water bodies and create terrain contours for finding water scarcity locations. Further this work also used some geospatial villages related data to obtain and analyze how many villages are suffering from critical water scarcity problems under the found water scarcity locations. The village’s data also highlights all village’s in which they fell under critical water scarcity regions and facing agriculture and drinking water problems, with respect to their elevation data and available nearby natural water resources.

Planning machine paths and row crop patterns on steep surfaces to minimize soil erosion

Soil erosion in arable fields is intensified on irregular surfaces. Although machine and crop-row patterns following terrain contours reduce runoff and increase water infiltration, these contours are almost never parallel while machine operations always are. In this work, a method is presented to generate patterns of machine paths on sloping land and assess their susceptibility to water erosion. The approach comprises three main process-steps: (1) assembling a comprehensive set of reference tracks and introducing hybrid contour lines; (2) adjust these curved tracks into steerable parallel tracks for agricultural machines; and (3) assess water flow accumulation and susceptibility to soil loss of the corresponding pattern. The methods were implemented in open source software and applied on three case studies concerning sugarcane production in the São Paulo region in Brazil. Our results suggest that soil loss could be reduced fivefold by inserting one single change in the cropping pattern while estimated reductions up to 75% could be obtained by the model when compared to a human-suggested coverage pattern.

Genfundne gravhøje i Nordjylland – Kartografiske studier

Genfundne gravhøje i Nordjylland – Kartografiske studier

A Comparison of Two Heavy Rainfall Events during the Terrain-Influenced Monsoon Rainfall Experiment (TiMREX) 2008

Abstract Two contrasting localized heavy rainfall events during Taiwan’s early summer rainy season with the daily rainfall maximum along the windward mountain range and coast were studied and compared using a combination of observations and numerical simulations. Both events occurred under favorable large-scale settings including the existence of a moisture tongue from the tropics. For the 31 May case, heavy rainfall occurred in the afternoon hours over the southwestern windward slopes after a shallow surface front passed central Taiwan. The orographic lifting of the prevailing warm, moist, west-southwesterly flow aloft, combined with a sea breeze–upslope flow at the surface provided the localized lifting needed for the development of heavy precipitation. On 16 June before sunrise, pronounced orographic blocking of the warm, moist, south-southwesterly flow occurred because of the presence of relatively cold air at low levels as a result of nocturnal and rain evaporative cooling. As a result, convective systems intensified as they moved toward the southwestern coast. During the daytime, the cold pool remained over southwestern Taiwan without the development of onshore/upslope flow. Furthermore, with a south-southwesterly flow aloft parallel to terrain contours, orographic lifting aloft was absent and preexisting rain cells offshore diminished after they moved inland. Over northern Taiwan on the lee side, a sea breeze/onshore flow developed in the afternoon hours, resulting in heavy thundershowers. These results demonstrate the importance of diurnal and local effects on determining the location and timing of the occurrences of localized heavy precipitation during the early summer rainy season over Taiwan.

Wetland inundation monitoring by the synergistic use of ENVISAT/ASAR imagery and ancilliary spatial data

Wetlands are among the most ecologically important ecosystems on Earth and their sustainability depends critically on the water resources. In a scenario of climate change and increased anthropogenic pressure, detailed monitoring of the water resources provides a fundamental tool to assess the ecosystem health and identify potential threats.Doñana wetlands, in Southwest Spain, dry out every summer and progressively flood in fall and winter to a maximum extent of 30,000ha. The wetland filling up process was monitored in detail during the 2006–2007 hydrologic cycle by means of twenty-one Envisat/ASAR scenes, acquired at different incidence angles in order to maximize the observation frequency. Flood mapping from the two uncorrelated ASAR channel data alone was proved unfeasible due to the complex casuistic of Doñana cover backscattering. This study addresses the synergistic utilization of the ASAR data together with Doñana's digital elevation model and vegetation map in order to achieve flood mapping.Filtering and clustering algorithms were developed for the automated generation of Doñana flood maps from the ASAR images. The use of irregular filtering neighborhoods adapted to the elevation contours drastically improved the ASAR image filtering. Edge preservation was excellent, since natural edges closely follow terrain contours. Isotropic neighborhoods were assumed of a single class and their intensities were averaged. As a result, intensity fluctuations due to speckle and texture over areas of the same cover type were smoothed remarkably.The clustering and classification algorithm operate on individual sub-basins, as the pixel elevation is more accurately related to the cover classes within them. Vegetation and elevation maps plus knowledge of Doñana backscattering characteristics from preceding studies were initially used to select seed pixels with high confidence on their class membership. Next, a region growing algorithm extends the seed regions with new pixels based on their planimmetric adjacency and backscattering Mahalanobis distance to the seeds.During the seed region growth, new pixels' possible classes are not constrained to their cover type according to the vegetation map, so the algorithm is able to capture temporal changes in the vegetation spatial distribution. Comparison of the resultant classification and concurrent ground truth yielded 92% of flood mapping accuracy. The flood mapping method is applicable to the available ASAR images of Doñana from six other hydrologic cycles.

3D Digitalization Modeling for Visualization of Dam Construction Process

It is established a visualization simulation mechanism of dam construction process at first. Then terrain contours are converted into grid mesh by contours discrete method to establish the terrain model. The 3D dam model, foundation pit, construction road are built. Then the dam model is digitalized to create the dam database. After that, all of the models are rendered by using 3DSMax, and then documents of models and materials are exported with a plugin of OgreMaxSceneExporter to assure that they can be identified by an effective graphics rendering engine--OGRE. Finally, a dam construction process visualization system for a practical case is developed, by which an interactive virtual reality environment is created for engineers and administrators.

Predicting terrain contours using a feed-forward neural network

Wheeled or tracked vehicles cannot move easily over much of the land surface of the earth. This paper describes research work to create walking machines that are able to travel when the terrain makes wheeled or tracked vehicles ineffective. These legged walking vehicles must be able to negotiate unknown environments with little or no knowledge of the terrain. A predictive terrain contour mapping strategy is proposed that uses a feed-forward neural network trained using a back-propagation algorithm to predict contours based on leg positions and orientations. The strategy is tested using the abilities of a tele-operated eight-legged robot named “ Robug IV”. Predicted performance is an improvement on previous implementations and a summarised comparison of the results for the four terrains is provided.

Orographic Effects on a Squall Line System over Taiwan

A north‐south-oriented, multicellular squall line during the Taiwan Area Mesoscale Experiment’s (TAMEX) intensive observation period 2 was studied, using dual-Doppler radar data, as it moved over the island of Taiwan. Over the open ocean, it moved eastward at a constant speed (;15.5 m s21). As the squall line encountered Taiwan Island’s complex mountainous areas, the leading edge moved slower in the mountain ridge areas than over the valleys. As a result, its orientation became approximately parallel to the terrain contours. In the upper levels, the eastward movement of the squall line aloft was less affected by the terrain compared to the low levels. As a result, the westward tilt of the rising motion at the front became less significant. Part of the system-relative rear-to-front flow entered the rising branch of the storm’s circulation as a result of orographic lifting, as illustrated by the trajectory analysis, and was enhanced by latent heat release. The system-relative rear-to-front flow did not appear to descend to the lowest levels. Furthermore, it is unlikely that the low-level cold pool behind the leading edge would move upslope. When the squall line moved over the higher terrain areas, the midlevel system-relative westerly flow from the rear entered the storm’s updraft. The vertical motion pattern was dominated by orographic lifting and sinking. Low-level system-relative frontto-rear inflow was absent. Weak echo maxima were found, mainly associated with orographic lifting ahead of or near the mountain peaks. These changes occurred within a short time (;40 min) after the squall line encountered the mountainous terrain. The environmental low-level wind ahead of the squall line exhibited a weak southerly flow west of the mountain ridge areas and a weak southwesterly flow in the valley areas because of island blocking. As a result, the low-level system-relative front-to-rear inflow was weaker in the valley areas than that in ridge areas. Nevertheless, the low-level moisture inflow from the front decreased rapidly in both the former and the latter areas when the squall line encountered mountainous terrain. This was attributed to a rapid decrease in the depth of the low-level inflow layer and less moisture availability in the higher terrain areas. The drier midlevel air entered the storm from the west with the echo tops decreasing as the squall line moved farther over the mountainous terrain.

Geographic representation of noticeability of aircraft noise in Grand Canyon National Park.

A novel geographic representation of the noticeability of aircraft noise that accounts for topographic relief has been constructed in a distributed computing environment. A regular grid of points spaced at 300-m intervals was superimposed over Grand Canyon National Park. Starting from digital elevation model data, GRASS geographic information system software running on a Sun workstation determined line-of-sight transects from each surface grid point to points on a complex system of aircraft flight paths. An acoustic propagation model based on algorithms of the U.S. Army Tank-Automotive Command’s ADRPM-7 software was then exercised on networked VAX and Butterfly computers to predict 1/3-octave-band aircraft noise levels produced by operation of a fleet of aircraft at each grid point. Bandwidth-adjusted signal-to-noise ratios were then calculated and returned to the Sun for construction of a new GRASS map layer of noticeability levels for the park. The new map can be color coded, draped over terrain contours, and rendered in perspective views for visualization purposes.

Terrain modeling for microwave landing system

A powerful analytical approach for evaluating the terrain effects on a microwave landing system (MLS) is presented. The approach combines a multiplate model with a powerful and exhaustive ray tracing technique and an accurate formulation for estimating the electromagnetic fields due to the antenna array in the presence of terrain. Both uniform theory of diffraction (UTD) and impedance UTD techniques have been employed to evaluate these fields. Innovative techniques are introduced at each stage to make the model versatile to handle most general terrain contours and also to reduce the computational requirement to a minimum. The model is applied to several terrain geometries, and the results are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Snowfall in high southern latitudes

Precipitation over Antarctica is an important climatic variable whose study has been limited by the frequent inability to discriminate between actual snow precipitation and drifting snow. Recent advances in point precipitation measurements promise to circumvent this problem. In addition, indirect estimates based upon the atmospheric water balance equation provide seasonal precipitation amounts for areas larger than 1×106 km². For broad‐scale studies in the continental interior net snow accumulation closely approximates precipitation. Annual precipitation is relatively high over the marginal ice slopes in relation to amounts in the interior. This meridional distribution is due to the orographic lifting of moist air by the ice sheet. Zonal precipitation variations are related to the quasi‐stationary cyclones in the circumpolar low‐pressure trough. Most precipitation falls in winter, when the average moisture content of the air is low. The intensity of cyclonic activity is the key factor governing the amount of precipitation and its variations. Precipitation generation in coastal regions is strongly influenced by the fact that poleward moving, moist maritime air masses are deflected by the steep marginal ice slopes to blow parallel to the terrain contours. Direct orographic lifting with accompanying adiabatic cooling is the dominant precipitation formation mechanism inland of the 1‐km elevation contour; intrusions of moist air far into the continent are accompanied by southerly winds through a deep tropospheric layer. Above 3000 m elevation where terrain slopes are gentle, radiative cooling is the primary mechanism by which saturation is maintained within moist air, and thus by which precipitation is formed. Most precipitation at these elevations falls from clear skies. This phenomenon does not differ from precipitation originating in clouds but is a direct result of the low moisture content of the air, and hence ice layers are optically too thin to be visible as clouds.