Digital Ground Research Articles

Forest stand height predicted from ICESat-2 ATLAS data for forest inventory and comparison to airborne laser scanning metrics

Abstract The study analysed 2019–2022 summertime canopy height predictions (H ICESat) given in ICESat-2 ATLAS dataset ATL08 for hemiboreal forests growing on an area of 40,000 km2 in Estonia around 25.6° E, 58.8° N. In total 12,711 ATL08 20×20 m pixel observations were used from 3,065 forest stands with homogenous canopy structure. Regression modelling was used to explain variability in ground surface elevation estimates, and relationships of H ICESat to basal area weighted mean tree height given in the forest inventory database (H FI) and to the 95th percentile of the vertical distribution of airborne laser scanning pulse return (H ALS). The other explanatory variables were the ICESat-2 ATLAS observation geographic location, ICESat-2 ATLAS track and beam energy indicators, forest canopy cover, evergreen coniferous tree dominance indicator, and deep peat soil indicator. The linear model between the Estonian digital terrain model elevation and ATL08 ground elevation had a determination coefficient of R2=99.97% and residual standard error of δ=0.51 m when a geographic location was included. The H FI can be predicted from H ICESat with R2=85% and δ=2.7 m. A comparison of means indicated that, on average, H ICESat was about 0.3 m greater than H FI. All the predictive variables (except the geographic location) were significant in canopy height models, and the best models fitted H ICESat with R2=95% and δ=1.6 m, however, there was no notable increase in R2 if more predictors than H ALS were added in the models. In practical applications using ATL08 data for forest inventories, the inclusion of weak energy beam observations increases the number of observations, but the beam energy indicator has to be included in the models.

Unmanned Aerial Vehicle-Neural Radiance Field (UAV-NeRF): Learning Multiview Drone Three-Dimensional Reconstruction with Neural Radiance Field

In traditional 3D reconstruction using UAV images, only radiance information, which is treated as a geometric constraint, is used in feature matching, allowing for the restoration of the scene’s structure. After introducing radiance supervision, NeRF can adjust the geometry in the fixed-ray direction, resulting in a smaller search space and higher robustness. Considering the lack of NeRF construction methods for aerial scenarios, we propose a new NeRF point sampling method, which is generated using a UAV imaging model, compatible with a global geographic coordinate system, and suitable for a UAV view. We found that NeRF is optimized entirely based on the radiance while ignoring the direct geometry constraint. Therefore, we designed a radiance correction strategy that considers the incidence angle. Our method can complete point sampling in a UAV imaging scene, as well as simultaneously perform digital surface model construction and ground radiance information recovery. When tested on self-acquired datasets, the NeRF variant proposed in this paper achieved better reconstruction accuracy than the original NeRF-based methods. It also reached a level of precision comparable to that of traditional photogrammetry methods, and it is capable of outputting a surface albedo that includes shadow information.

Abdominal MR Multitasking for radiotherapy treatment planning: A motion-resolved and multicontrast 3D imaging approach.

Radiotherapy treatment planning (RTP) using MR has been used increasingly for the abdominal site. Multiple contrast weightings and motion-resolved imaging are desired for accurate delineation of the target and various organs-at-risk and patient-tailored planning. Current MR protocols achieve these through multiple scans with distinct contrast and variable respiratory motion management strategies and acquisition parameters, leading to a complex and inaccurate planning process. This study presents a standalone MR Multitasking (MT)-based technique to produce volumetric, motion-resolved, multicontrast images for abdominal radiotherapy treatment planning. The MT technique resolves motion and provides a wide range of contrast weightings by repeating a magnetization-prepared (saturation recovery and T2 preparations) spoiled gradient-echo readout series and adopting the MT image reconstruction framework. The performance of the technique was assessed through digital phantom simulations and in vivo studies of both healthy volunteers and patients with liver tumors. In the digital phantom study, the MT technique presented structural details and motion in excellent agreement with the digital ground truth. The in vivo studies showed that the motion range was highly correlated (R2 = 0.82) between MT and 2D cine imaging. MT allowed for a flexible contrast-weighting selection for better visualization. Initial clinical testing with interobserver analysis demonstrated acceptable target delineation quality (Dice coefficient = 0.85 ± 0.05, Hausdorff distance = 3.3 ± 0.72 mm). The developed MT-based, abdomen-dedicated technique is capable of providing motion-resolved, multicontrast volumetric images in a single scan, which may facilitate abdominal radiotherapy treatment planning.

Analysis of stress field in the head area of the Three Gorges Reservoir based on coupled fluid-solid theory

The Three Gorges Reservoir, one of the largest water conservation system in the world, has been of keen interest to scientists globally since its impoundment. After construction of the dam, there has been a significant increase in seismic activity in the head area of the reservoir. It is generally accepted that earthquakes in this region are predominantly caused by the Jiuwanxi and Xiannvshan faults. This study focused on the stress changes occurring in the research area. A three-dimensional finite element model of the reservoir area was constructed using the geological structure and digital ground elevation data of the reservoir area. The fluid-solid coupling theory was applied to calculate the dynamic spatial changes in pore pressure and Coulomb stress in the faults and surrounding rocks during reservoir impoundment. The findings indicated that the added head pore water pressure at the bottom of the reservoir had a maximum impact range of approximately −2800 m on the surrounding rock, whereas the Xiannvshan and Jiuwanxi faults had a maximum diffusion range of approximately −4300 m. Rock permeability also played a significant role in the water storage process. During the 1 56 m water impoundment stage, owing to rapid water storage activity, stress could not be transmitted to both sides in a timely manner, resulting in the formation of an extreme stress change zone at −4000 m inside the fault. This may have been the reason for the frequent earthquakes during this stage. The 17 5 m cycle water storage stage also exhibited a significant degree of seismicity, potentially attributable to the long-term infiltration of reservoir water and accumulation of stress in the previous stage. The stress in the study area at the four stages are in a process of accumulation-release-accumulation-release.

Method for extracting temperature distribution characteristics of municipal asphalt pavement construction in high-temperature weather under compaction quality constraint

ABSTRACT In order to improve the temperature detection ability of municipal asphalt pavement in high-temperature weather, a method to extract the temperature distribution characteristics of municipal asphalt pavement in high-temperature weather under the constraint of compaction quality was proposed. Using a digital image system, laser profiler, and ground penetrating radar system, collect construction temperature data of urban asphalt pavement under the constraints of compaction quality under high-temperature weather conditions, and use time series analysis to reconstruct the data. Combined with the nondestructive detection method of ground penetrating radar, the echo analysis model of temperature information is established, and the characteristics of temperature distribution are reconstructed using the spectral analysis method. The time–frequency transformation method is used to transform the time series of construction temperature under the constraint of compaction quality. The discrete signal window method was used to analyse the temperature characteristics of construction. According to the characteristic state monitoring, the temperature distribution characteristics are extracted. The test results show that the method is reliable in extracting the temperature distribution characteristics of municipal asphalt pavement construction under high-temperature weather and improves the real-time monitoring capability of asphalt pavement temperature.

Research on Visualization of Digital Ground Model Based on Satellite Image

3D printing technology has the advantages of high precision, low cost and environmental protection, and can provide a new and reliable technology for visual expression. This paper takes Qinghai Lake as the research object, uses remote sensing technology as the means to make a digital ground model, uses 3DMax software to convert geographic information data into data that can be visualized and expressed, and finally uses 3D printing technology to make a visual 3D solid model of Qinghai Lake basin. The experiment shows that 3D printing technology is feasible in the production of digital terrain model, and has broad prospects for development.

Aircraft Upset Recovery Strategy and Pilot Assistance System Based on Reinforcement Learning

The upset state is an unexpected flight state, which is characterized by an unintentional deviation from normal operating parameters. It is difficult for the pilot to recover the aircraft from the upset state accurately and quickly. In this paper, an upset recovery strategy and pilot assistance system (PAS) based on reinforcement learning is proposed. The man–machine closed-loop system was established and the upset state, such as a high angle of attack and large attitude angle, was induced. The upset recovery problem was transformed into a sequential decision problem, and the Markov decision model of upset recovery was established by taking the deflection change of the control surface as the action. The proximal policy optimization (PPO) algorithm was selected for the strategy training. The adaptive pilot model and the reinforcement learning method proposed in this paper were used to make the aircraft recover from the upset state. Based on the correspondence between the flight state, the recovery method, and the recovery result, the aircraft upset recovery safety envelopes were formed, and the four-level upset recovery PAS with alarm warning, coordinated control, and autonomous recovery modes was constructed. The results of the digital virtual flight simulation and ground flight test show that compared with a traditional single pilot, the aircraft upset recovery strategy, the upset recovery safety envelopes, and the PAS established in this study could reduce the handling burden of the pilot and improve the success rate and effect of upset recovery. This research has certain theoretical reference values for flight safety and pilot training.

Remote sensing campaign at the Roman Villa of Caddeddi on the Tellaro river (Noto, Italy)

The Villa of Caddeddi, in the territory of Noto (Siracusa) is located on the south bank of the Tellaro river, about 3 km from its mouth. The site, interpreted as a rural luxury residence dated to the fourth–fifth century CE, was first discovered in 1972 and intermittently investigated in the subsequent decades and mostly studied from the perspectives of the splendid mosaic floors there uncovered. The excavated structure accounts for just a portion of the complex, which is partially covered by an eighteenth–nineteenth century farmhouse. After a long period of neglect, the villa, mainly known in literature for its exquisite mosaic floors, has been recently restored and opened to the public and become subject of new studies by the University of South Florida’s Institute for Digital Exploration (IDEx) and the Institute of Heritage Science – CNR which between 2019 and 2022 conducted a remote sensing, using ground penetrating radar method, campaign in partnership with the Parco Archeologico e Paesaggistico di Siracusa, Eloro, Villa del Tellaro e Akrai. The results related to the digital exploration and ground penetrating radar allow new knowledge relating to the Roman villa and allows a scientific reconstruction of the villa.

A 2D/3D multimodal data simulation approach with applications on urban semantic segmentation, building extraction and change detection

Advances in remote sensing image processing techniques have further increased the demand for annotated datasets. However, preparing annotated multi-temporal 2D/3D multimodal data is especially challenging, both for the increased costs of the annotation step and the lack of multimodal acquisitions available on the same area. We introduce the Simulated Multimodal Aerial Remote Sensing (SMARS) dataset, a synthetic dataset aimed at the tasks of urban semantic segmentation, change detection, and building extraction, along with a description of the pipeline to generate them and the parameters required to set our rendering. Samples in the form of orthorectified photos, digital surface models and ground truth for all the tasks are provided. Unlike existing datasets, orthorectified images and digital surface models are derived from synthetic images using photogrammetry, yielding more realistic simulations of the data. The increased size of SMARS, compared to available datasets of this kind, facilitates both traditional and deep learning algorithms. Reported experiments from state-of-the-art algorithms on SMARS scenes yield satisfactory results, in line with our expectations. Both benefits of the SMARS datasets and constraints imposed by its use are discussed. Specifically, building detection on the SMARS-real Potsdam cross-domain test demonstrates the quality and the advantages of proposed synthetic data generation workflow. SMARS is published as an ISPRS benchmark dataset and can be downloaded from https://www2.isprs.org/commissions/comm1/wg8/benchmark_smars/.

Appraisal of Water Resources Development Action Plan for Groundwater Recharge in Raghunathapalli Watershed, Jangaon District, Telangana State, India

Water is elixir of life which needs regular assessment for maintaining ecological balance. Micro watershed wise (a few thousand hectares of extent) water resource action plan is need of the hour especially for a hard rock terrain like Raghunathapalli watershed of Jangaon District. Geologically, the area is underlain by Quartzite and Pelitic Schist of Older Metamorphics and Leuco Granite / Grey Alkali FelpsarGranite Terrain (Peninsular Gneissic Complex) belonging to Archeans. The Archeans are intruded at several places by several Pegmatite Veins and Basic Dolerite Dykes. The average annual rainfall of the study area for the past 19 years is 946 mm and that of monsoonal rainfall is 746 mm. In order to do artificial ground water recharge, the study and analysis of parameters that control the ground water recharge is very important for effective ground water recharge. The spatio-temporal variations in rainfall, regional/local distribution in geological formations and geomorphic composition of various units have led to uneven occurrence and distribution of water resources. Different thematic layers like Geology, Geomorphology, Stream Network, Micro Watersheds, Digital Elevation Model, Contours (2m), Base Layers, Soil and Ground Water Potential maps are prepared using Geospatial technologies like Remote Sensing & GIS. Existing Recharge Structures are marked using 1:25,000 scale Survey of India Toposheets and new locations are updated with high resolution satellite imagery. Micro watershed wise Water Balance studies are carried out and Water Resources Development Action Plan is prepared using Ridge to Valley concept with new artificial recharge structures like Check Dams (22), Percolation Tanks (10), Contour Trenches (68Kms), Subsurface Dyke (2), Farm Pond (268), Recharge Pit (179), Recharge Shaft (16), Desilting Tank (24 nos) etc at suitable terrain conditions. Newly proposed locations for constructions of Rainwater harvesting structures in the gap areas will improve the ground water regime and improves the sustainability of wells for agriculture in the drought prone area of Raghunathapalli watershed. Thus Geospatial technologies are cost effective tools for management and conservation of water resources.

Project Unplug - A Personal Reflection on Rediscovering the Joy in Being Online

In 2021 I realised that large swathes of the Internet were making me sad. I resolved to do something about it. The result was a focused, intense process of finding the mechanisms by which I could optimise my relationship with the online world. I resolved to focus on those things that brought me sustained happiness, as opposed to those things that merely offered transient pleasure. I ripped toxic websites out of my life, and limited my exposure to those I regarded as merely hazardous. The result was a battle to regain joy I once experienced in my online leisure activities - to regain my focus on electronic common ground, as opposed to digital battle grounds. Few technologies have reached so deeply into our lives - and into our sense of self - as the modern Internet. Social and psychological defence mechanisms that evolved for the context of a tribe simply do not survive at Internet scale. For all that social media is designed to link us together, in many ways it only serves to push us apart. This paper is a personal, autoethnographic reflection of how 'Project Unplug' was conceptualised, prepared, and executed over 2022. The specific combination of online vectors that were the cause of my unhappiness are unique to me. This paper though outlines a hopefully valuable approach to creating our own digital rituals and rites so as to create strong, inviolable limits on the extent to which the Internet might erode our personal happiness

Phaselet Transform-Based Digital Ground Fault Protection of Grid-Connected Photovoltaic Systems

The growing interests in utilizing Photovoltaic (PV) systems are usually faced with challenges of accurate and reliable protection of these distributed generation units. A desired protection of PV systems has to effectively and accurately detect and respond to internal faults (within the PV system) and external faults (in the host grid and/or fed loads). This paper presents and tests the performance of a digital ground fault protection (DGFP) for grid-connected PV systems. The presented DGFP detects faults based on the energy contents of high frequency sub-bands of the ground current. These energy contents are extracted using the phaselet transform that can process signals with non-stationary variations in their phases. Energy contents of the high frequency sub-bands can provide accurate, fast, and reliable detection and identification of faults experienced by a PV system operated. The phaselet transform (PHT)-based DGFP is implemented for performance testing using PV systems that are operated in the grid-connected mode, and subjected to various fault and non-fault events. Performance results demonstrate accurate, fast, and reliable detection and response to different types of fault and non-fault events. Response features of the PHT-based DGFP are complimented with minor sensitivity to the level of power production and/or type and location of faults.

Political satire as alternative journalism in Indian stand-up comedy

Political Satire has changed the way we view comedy. It would be accurate to say that real journalism is more evident in stand-up comedies and less in productive news channels that are also known as the fourth pillar of democracy. Journalism has turned into a laughingstock with all the unnecessary screaming, shouting and pointless/baseless debates. Digital platform has opened its arms wide to memes, stand-up comedies and sitcoms which are not only a visual treat to the audience but has in a way affected day to day lives of people reigning from different walks of life. Political satire through the digital ground has changed the way we perceive politics. Today’s political satire, put forth in the form of stand-up comedies, situational comedies and memes, debunks the status quo. They have revolutionised the content and our perception as to how we perceive important political events. Satire carries the ability to bring about a change in society. This paper is an attempt to understand the journey of Indian Stand-up comedy as an important tool for political satire and how in recent years this has taken the form of alternative journalism.

Forecasting landslides using community detection on geophysical satellite data.

As a result of extreme weather conditions, such as heavy precipitation, natural hillslopes can fail dramatically; these slope failures can occur on a dry day, due to time lags between rainfall and pore-water pressure change at depth, or even after days to years of slow motion. While the prefailure deformation is sometimes apparent in retrospect, it remains challenging to predict the sudden transition from gradual deformation (creep) to runaway failure. We use a network science method-multilayer modularity optimization-to investigate the spatiotemporal patterns of deformation in a region near the 2017 Mud Creek, California landslide. We transform satellite radar data from the study site into a spatially embedded network in which the nodes are patches of ground and the edges connect the nearest neighbors, with a series of layers representing consecutive transits of the satellite. Each edge is weighted by the product of the local slope (susceptibility to failure) measured from a digital elevation model and ground surface deformation (current rheological state) from interferometric synthetic aperture radar (InSAR). We use multilayer modularity optimization to identify strongly connected clusters of nodes (communities) and are able to identify both the location of Mud Creek and nearby creeping landslides which have not yet failed. We develop a metric, i.e., community persistence, to quantify patterns of ground deformation leading up to failure, and find that this metric increased from a baseline value in the weeks leading up to Mud Creek's failure. These methods hold promise as a technique for highlighting regions at risk of catastrophic failure.

DESIGN AND MODELLING OF GROUND PROXIMITY WARNING SYSTEM (GPWS) FOR TRAINING AID

Controlled flight into terrain (CFIT) is the most common type of aircraft crashes in the world of aviation today. Following the sheer volume of terrain collisions, there was an introduction of CFIT classification to enable the grouping into one category of all crashes involving aircrafts colliding with terrains. To avert CFIT accidents, the Ground Proximity Warning System (GPWS) was introduced onboard the aircraft for the flight crew to be aware of the moment the aircraft is approaching a ground terrain via automatic and very distinct acoustic warning. This paper presents a digital display ground proximity warning system as a teaching aid with audio prompt using ultrasonic sensor to produce forward distance from aircraft to obstacle ahead, height, inclination of aircraft in relation to its terrain beneath the aircraft and a digital computer interface for instrument visualization for better performance using graphic user interface (GUI) thereby enabling clearer understanding on GPWS. The Arduino IDE using Arduino sketch and C language were used on the Arduino Uno. The aircraft was integrated with different electronic modules which includes Arduino single board, Ultrasonic sensor, accelerometer and transceiver module, and all these uses the Arduino to read the signal from the sensor, processes and transmit to the base station wirelessly via radio frequency. Simulation results indicates that the responses of the models are a replica of the actual aircraft operations.

NDT spatial data integration for monumental buildings: technical information management for the Royal Alcazar of Seville

ABSTRACT Non-destructive testing (NDT) for the diagnosis of heritage buildings has proved to be one of the most sustainable approaches in the field of preventive conservation. Nevertheless, the comprehensive management of NDT information is complex, often resulting in a poorly optimized use of the data. This contribution aims to propose a method for integrating NDT data in a standardized way into simplified digital information models, produced using Geographic Information Systems (GIS). This method is applied to the plasterwork located in the Courtyard of the Maidens, which are elements with an enormous historic-artistic value in the Royal Alcazar of Seville (Spain), a significant UNESCO monument. For this purpose, a multi-scale web GIS-based model has integrated the NDT information from the plasterworks, such as ambient conditions, damage mapping, C-Shore Hardness, Superficial Humidity, Infrared thermography (IRT), Digital Image Processing (DIP) and Ground Penetration Radar (GPR). The combined georeferencing of the data from the various measurements and their simultaneous visualization has enabled the detection of vulnerable areas in the complex. The results are easily accessible for managers, and additionally show the analytical potential of the research approach, thereby allowing a quick diagnosis and hierarchization of tasks.

Research and development of tunnel intelligent design system

According to the characteristics of tunnel design, the tunnel BIM entity is created based on the digital ground model, forming a set of data sources, two-dimensional drawings, three-dimensional models and three expression design forms of BIM building information. The system can complete the design of tunnel building boundaries and internal contours, tunnel lining design, cave door design and auxiliary construction measures design; Among them, intelligent design is a feature of the software: the design of the cave door, lining section and auxiliary measures can be intelligently determined through the information such as the type of surrounding rock and the burial depth of the tunnel in the geological data, so as to realize the digitization and intelligence of the tunnel design. In addition, there is a template library function, a timely update function. At present, the system can meet 80% of the business needs of tunnel design, which greatly improves the design production efficiency.

Khel Tale: An Interactive Animated Storybook App for Children

According to the current study, children adores reading fairy tales or comics since their childhood. In today’s world, digital grounds have transformed storybooks into animated illustrations. In particular, famous studios like Disney are producing movies out of them to attract and influence millions of children. However, moral based stories have always been in demand to teach children that how to pay heed to the elder’s advice. Also, how to morally transform their behavior in a positive manner. Khel Tale is a modern version of animated storybook application for children to play which asks them to pick one of the main characters of their own choice, out of the story. Thus, children enjoy the consequences of making those choices at the end of the story. It is a choice based animated storybook that plays 3D animation clips in order to narrate the whole story to children through pictorial illustrations. The main purpose of this mobile application is to teach children regarding the importance of obeying the instructions of their elders through decision-based 3D animated stories. The application runs in landscape mode and is divided into further episodes. The content of each episode covers a small lesson for children. An episode begins by playing a fixed 3D animation video clip, and later on it offers two choices to children in order to particularly conclude the episode either with a good choice or a bad choice. Later, children can also see the consequences of their choices and actions in the story. The basic concept of this application revolves around a thought that mostly children are fascinated by the characters they observe in cartoons and read in stories. Hence, they start relating them to those characters. This concept is evolved by combining the approach of teaching to children through 3D animated stories where they can choose the characters to see the reaction of not listening to their elders. They also observe that what reward they can get if they actually act patient and listen to what elders advised them. Hence, the current study regarding Khel Tale application concludes it with the effectiveness. 
 Index Terms: Animated storybook, audio dubbing, computer animations, Khel Tale, teaching good behavior, 3D and 2D visual models

Photogrammetry and GIS to investigate modern landscape change in an early Roman colonial territory in Molise (Italy)

Legacy data in the form of historical aerial imagery can be used to investigate geomorphological change over time. This data can be used to improve research about the preservation and visibility of the archaeological record, and it can also aid heritage management. This paper presents a composite Image-Based Modelling workflow to generate 3D models, historical orthophotos, and historical digital elevation models from images from the 1970s. This was done to improve the interpretation of survey data from the early Roman colony of Aesernia. The main challenge was the lack of high-resolution recent digital elevation models and ground control points, and a general lack of metadata. Therefore, spatial data from various sources had to be combined. To assess the accuracy of the final 3D model, the RMSE was calculated. While the workflow appears effective, the low accuracy of the initial data limits the usefulness of the model for the study of geomorphological change. However, it can be implemented to aid sample area selection when preparing archaeological fieldwork. Additionally, when working with existing survey datasets, areas with a high bias risk resulting from post-depositional processes can be indicated.

Application of Multimedia Tilt Photogrammetry Technology Based on Unmanned Aerial Vehicle in Geological Survey

In order to better investigate the geological research, a tilt photogrammetry technology based on the unmanned aerial vehicle is proposed. This paper makes use of UAV tilt photogrammetry technology to make geological macroscopic analysis and establishes 3d color digital ground model, forming a set of technical methods for geological survey assisted by UAV. The experimental results show that the coordinate calculation is significantly improved, and the root mean square error of plane coordinates reaches 0.2 m, which can meet the requirements of later cartography and spatial measurement. The feasibility and efficiency of carrying out a geological survey based on the unmanned aerial vehicle are verified by the practical application in landslide hazard geological survey. It is proved that DEM and DOM data obtained based on oblique photogrammetry data can form various thematic maps by superimposing them with vector GIS data, which will provide a basic data model for subsequent engineering investigation, site management, and image display.