Quarry wall stability and design optimisation using photogrammetric mapping and analysis techniques

The new generation of 50cm resolution stereo satellite photos are demonstrated to have relative horizontal accuracies in the range of 10cm in 10km. Using sophisticated image matching, signal enhancement and noise attenuation methods “borrowed” from the field of oil and gas exploration seismic processing, elevation maps with better than 50cm vertical accuracy, on 1m centers, can be produced from these 50cm stereo satellite photos. We call our processing of Digital Elevation Models (DEMs) from stereo satellite photos “geophysical processing” to differentiate it from the conventional photogrammetric stereo photo elevation mapping methods. This new geophysical stereo satellite elevation processing method produces stereo satellite DEMs with significantly better horizontal resolutions and vertical accuracies then the conventional photogrammetric processes. The resolution and accuracy of these high resolution geophysical stereo satellite DEMs has been demonstrated with thousands of ground survey points and by direct comparison with LiDAR DEMs. In areas of sparse vegetation the 1m posted DEMs produced from 50cm stereo satellite photos have demonstrated elevation accuracies of better than 50cm RMSE. These stereo satellite DEMs have resolutions and accuracies similar to high quality LiDAR DEMs.

<p>Active rock glaciers in Greenland have been studied since the 1980s focusing on two regions (Disko Island and Zackenberg) located north of 69°13’N. As judged from permafrost models, widespread existence of permafrost and thus active rock glaciers are also possible south of this latitude. Therefore, research on a large rock glacier on the island of Bjørneø (size: 1 km²; elevation 250-600 m a.s.l.; NNW-exposed) at 64°30’N was initiated in 2016. Research focused until 2020 on repeated differential GPS measurements at several fixed ground control points, on the analysis of the bottom temperature of the winter snow cover, and on the assessment of high-resolution orthophotos and digital terrain models based on UAV campaigns. Results up to 2020 indicate that permafrost influences a large part of the rock glacier and surface displacement takes place in the order of cm per year particularly in the central part.</p><p>Within an INTERACT research project we continued and expanded research at this rock glacier in 2021 applying two types of geophysics (electrical resistivity tomography, ground penetrating radar), differential GPS, relative surface dating, geomorphic mapping, clast form analysis, and monitoring of ground, air, and water temperatures. We find that widespread permafrost is likely along the measured geophysical profiles, that ground and water temperatures generally support the assumption of present permafrost conditions, and that the rock glacier evolved over a period of several thousand years, starting to form soon after the recession of the Greenland Ice Sheet from the coast some 10.4 to 11.4 ka BP.</p><p>In addition to fieldwork, different types of remote sensing- and modelling based research at this rock glacier were accomplished. Clast size distribution was semi-automatically quantified using a high-resolution digital terrain model. Results reveal distinct clast size-differences along a longitudinal profile of the rock glacier. Analyses of time-series of Sentinel-1 differential SAR interferograms for the period 2016 to 2021 showed minor motion in the uppermost part of the landform during a period of two months, distinct compressive flow (few cm) of two lobes of the landform after several months, and landform-wide movement over a period of 3 years. The terrain surface before the formation of the rock glacier, and thus the rock glacier volume, were reconstructed on the basis of field observations and terrain data. The volume of material relocated due to rock glacier activity was approx. 10 million m³. Finally, the present rock glacier extent and morphology were numerically reproduced as a steadily evolving and slowly moving viscous mass using a model implemented in the GIS-based open-source mass flow simulation framework r.avaflow.</p><p>Our chosen multidisciplinary approach is a significant step forward in understanding the long-term evolution and present conditions of large rock glacier systems in the low Arctic region of Greenland.</p>

Image matching as a data source for forest inventory – Comparison of Semi-Global Matching and Next-Generation Automatic Terrain Extraction algorithms in a typical managed boreal forest environment

With the realization of the Shuttle Radar Topographic Mission (SRTM) and the distribution of the 3 arcsec (90 m) data over Europe, a high-resolution digital terrain model (DTM) became available for Greece. Until today, high-resolution DTMs for Greece were generated by the Hellenic Military Geographic Service (HMGS) only and present variable resolutions with the finest one being set to 100 m. These DTMs were usually determined by digitizing topographic maps and are thus of variable and sometimes unknown accuracy. When a high-resolution, e.g., 0.5 - 1 arcmin geoid is needed, it is absolutely necessary to employ a very high resolution DTM to compute the terrain effects to gravity and the indirect effect to the geoid. If this information is not available and a coarser DTM is used, then the topographic effects computed are aliased, due to the insufficient resolution of the topographic data used. The scope of this work is twofold. First, a validation and accuracy assessment of the SRTM 90 m DTM over Greece is performed through comparisons with existing global models, like GLOBE and GTOPO30, as well as with the Greek 450 m DTMs delivered by HMGS. Whenever a misrepresentation of the topography is identified in the SRTM data, it is “corrected” using the local 100 m DTM. This processes resulted in an improved SRTM DTM called SRTMG, which was then used to determine terrain and RTM effects to gravity field quantities. Then, all available DTMs were used to compute terrain effects on both gravity anomalies and geoid heights at variable spatial resolutions. From the results acquired, the performance of the SRTMG model with respect to geoid modeling was assessed and conclusions on the effect of the DTM resolution were drawn.

A rapid high-resolution multi-sensory urban flood mapping framework via DEM upscaling

Remote geotechnical mapping of two large rock cuttings on a vital transportation corridor in North Queensland was undertaken to provide input data for stability analysis and design of stabilisation elements. The mapping approach described utilised state-of-the-art digital photogrammetry tools to allow the collection of structural data from large areas where direct access to the slopes for conventional (tape measure and compass) mapping was either not possible or very limited without the use of rope access methods. The photogrammetric method employed allowed the mapping to be completed rapidly and safely, without affecting the serviceability of the roadway during the site investigation. It provided measurements of the orientation, spacing and persistence of the rock discontinuities that control the stability of the cuttings. It also provided detailed digital terrain models (DTMs) of the slopes, which provided critical topographic information for input to the analysis and design processes. In recent years, the use of digital photogrammetry as a tool to collect structural and geotechnical mapping data from large rock cuttings has become commonplace in the mining industry. The application of this method to civil engineering problems on the other hand has been far less common, but comes as a natural progression as this technology becomes more user-friendly and cost-effective.

A New South Polar Digital Terrain Model of Mars from the High-Resolution Stereo Camera (HRSC) onboard the ESA Mars Express

Focused on the Stromboli Island, this research investigates whether airborne remote sensing systems, such as those based on digital photogrammetry and laser scanner sensors, can be adopted to monitor slope deformation and lava emplacement processes in active volcanic areas. Thanks to the capability of extracting accurate topographic data and working on flexible time schedule these methods can be used to constrain the regular and more frequent measurements derived from satellite observations. In this work we present an application dedicated to the monitoring of Stromboli volcanic edifice useful to obtain quantitative data on the geometry of deformation features and the displaced (failures and landslides) and emplaced (lava flows) volumes. In particular, we focused on the capability of extracting average effusion rates from volume measurements that can be used to validate or integrate satellite derived estimates are often affected by biases which are not easily detectable. Since 2001 a number of airborne remote sensing surveys, namely Digital Photogrammetry (DP) and Airborne Laser Scanning (ALS), were carried out on Stromboli volcano to obtain high resolution digital terrain models (DEM) and orthophotos characterized by sub-meter spatial resolution and time schedule suitable for monitoring the morphological evolution of the surface during the quiescent phases. During the last two effusive eruptions (2002-2003 and 2007) the surface modifications, suffered by the Sciara del Fuoco slope and by the crater area as a consequence of effusive activity, were quantified and controlled using the same methodologies. This work is mainly focused on the 2007 eruption but also accounts for analogies and differences with the 2002-2003 event being based on a multi-temporal quantitative analysis of the data collected from 2001 to 2007. The 2007 eruption involved the Sciara del Fuoco slope from the 27th February until the 2nd April: five flows produced a compound lava field including a lava delta on the shoreline and discharging most of the lava into the sea. The comparison of the 2007 DEMs with a pre-eruption surface (2006 LIDAR survey) allowed evaluating the total lava volume emplaced on the slope while two syn-eruption DEMs were used to calculate the average effusion rates through the eruption. Finally hypothesis on the lava discharge and slope instability mechanisms, which appear strongly connected, are formulated.

Hong Kong is one of the world's mountainous international cities, and landslides are a constant threat to human life and property. Monitoring landslides in Hong Kong is important and this is always done by field surveying. However, although conventional survey techniques provide accurate landslide information, they are limited to small areas and physical contact with the slope may be dangerous. Remote sensing techniques can provide an alternative for collecting information about landslide causes and occurrences, and they may assist in the prediction of future landslide occurrences. This article demonstrates the use of monoscopic and stereoscopic aerial photographs, along with satellite images from the IKONOS very high resolution (VHR) sensor for detailed landslide hazard assessment over Hong Kong. For monoscopic aerial photographs, a fusion technique for generating pseudo true colour images from false colour aerial photographs was demonstrated. The pseudo true colour image is useful for better visual analysis in the photogrammetric model. For monoscopic IKONOS image, a set of image fusion techniques was applied in order to improve landslide interpretation, and the results were examined visually and statistically. The Pan-sharpening method among all the image fusion techniques has been demonstrated to have superior performance for identifying both landslide trails and crowns. Stereoscopic viewing using a stereoscopic pair of aerial photographs and stereoscopic IKONOS images was employed for more detailed landslide investigation such as landscape positional relationships (e.g. streams and ridges). Digital elevation models (DEM) were generated from aerial photographs and IKONOS stereoscopic images, and they were compared with digital contour data with 2 m contour interval. The DEMs generated from digital photogrammetric model and IKONOS stereoscopic images are consistently more accurate than an existing DEM, and are sensitive to micro-scale terrain features. The Hong Kong Civil Engineering Department may use the derived monoscopic fused images, stereoscopic images, DEM and anaglyph as objective measures for a detailed landslide study within Hong Kong.

We demonstrate the creation of a large area of high-resolution (260 × 209 km2 at 1 m/pixel) DTM mosaic from the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images over the Chang’E-4 landing site at Von Kármán crater using an in-house deep learning-based 3D modelling system developed at University College London, called MADNet, trained with lunar orthorectified images and digital terrain models (DTMs). The resultant 1 m DTM mosaic is co-aligned with the Chang’E-2 (CE-2) and the Lunar Orbiter Laser Altimeter (LOLA)—SELenological and Engineering Explorer (SELENE) blended DTM product (SLDEM), providing high spatial and vertical congruence. In this paper, technical details are briefly discussed, along with visual and quantitative assessments of the resultant DTM mosaic product. The LROC NAC MADNet DTM mosaic was compared with three independent DTM datasets, and the mean differences and standard deviations are as follows: PDS photogrammetric DTM at 5 m grid-spacing had a mean difference of −0.019 ± 1.09 m, CE-2 DTM at 20 m had a mean difference of −0.048 ± 1.791 m, and SLDEM at 69 m had a mean difference of 0.577 ± 94.940 m. The resultant LROC NAC MADNet DTM mosaic, alongside a blended LROC NAC and CE-2 MADNet DTM mosaic and a separate LROC NAC, orthorectified image mosaic, are made publicly available via the ESA planetary science archive’s guest storage facility.

Convolutional Neural Networks (CNNs) play a vital role in machine learning. CNNs are typically both computing and memory intensive. Emerging resistive random-access memories (RRAMs) and RRAM crossbars have demonstrated great potentials in boosting the performance and energy efficiency of CNNs. Compared with small crossbars, large crossbars show better energy efficiency with less interface overhead. However, conventional workload mapping methods for small crossbars cannot make full use of the computation ability of large crossbars. In this paper, we propose an Overlapped Mapping Method (OMM) and MIxed Size Crossbar based RRAM CNN Accelerator (MISCA) to solve this problem. MISCA with OMM can reduce the energy consumption caused by the interface circuits, and improve the parallelism of computation by leveraging the idle RRAM cells in crossbars. The simulation results show that MISCA with OMM can achieve 2.7× speedup, 30% utilization rate improvement, and 1.2× energy efficiency improvement on average compared with fixed size crossbars based accelerator using the conventional mapping method. In comparison with GPU platform, MISCA with OMM can perform 490.4× higher on average in energy efficiency and 20× higher on average in speedup. Compared with PRIME, an existing RRAM based accelerator, MISCA has 26.4× speedup and 1.65× energy efficiency improvement.

Background/Objectives: The vast amounts of high-quality data stored in relational databases (RDB) is the primary resources for Linked Open Data (LOD) datasets. This paper proposes a schema-based mapping approach from RDB to RDF, which provides succinct and efficient mapping.Methods/Statistical analysis: The various approaches, languages and tools for mapping RDB to LOD have been proposed in the recent years. This paper surveys and analyzes classic mapping approach and language such as Direct Mapping and R2RML. The mapping approaches can be categorized by means of their data modeling. After analyzing the conventional RDB-RDF mapping methods, this paper proposes a new mapping method and discusses its typical features and applications.Findings: There are two types of mapping approaches for the translation of RDB to RDF: instance-based and schema-based mapping approaches. The instance-based mapping approaches generate large amounts of RDF graphs by means of mapping rules. These approaches causes data redundancy since the same data is stored in two ways of RDB and RDF. It is very easy to bring the data inconsistence problem when data update operations occur. The schema-based mapping approaches can effectively avoid data redundancy since the mapping can be accomplished in the conceptual schema level.The architecture of SPARQL endpoint based on schema mapping approach consists of five phases:Generation of mapping description based on mapping rules.SPARQL query statements for RDF graph patterns.Translation of SPARQL query into SQL query.Execution of SQL query in RDB.Interpretation of SQL query result into JSON-LD format.Experiments show the schema-based mapping approach is a straightforward, succinct and efficient mapping method for RDB2RDF.Improvements/Applications: This paper proposes a schema-based mapping approach called R2RS, which shows better performance than the conventional mapping methods. In addition, R2RS also provides the efficient implementation of SPARQL endpoint in RDB.

The application of the automated analysis of remote sensing data processed into high-resolution digital terrain models (DTMs) using geographic information systems (GIS) tools provides a geomorphometric characterization of the diversity of the relief of loess patches over large areas. Herein, a quantitative classification of 79 loess patches with a total area of 3361 km2, distributed within the eastern part of the Polish Uplands belt, is carried out. A high-resolution 1 × 1 m DTM was generated from airborne laser scanning (ALS) data with densities ranging from 4 pts/m2 to 12 pts/m2, which was resampled to a resolution of 5 × 5 m for the study. This model was used to classify landform surfaces using the r.geomorphon (geomorphon algorithm) function in GRASS GIS software. By comparing the values in the neighborhood of each cell, a map of geomorphometric features (geomorphon) was obtained. The classification and typology of the relief of the studied loess patches was performed using GeoPAT2 (Geospatial Pattern Analysis Toolbox) software. Pattern signatures with a resolution of 100 × 100 m were extracted from the source data grid, and the similarity of geomorphological maps within the signatures was calculated and saved as a signature file and segment map using the spatial coincidence method. The distance matrix between each pair of segments was calculated, and the heterogeneity and isolation of the maps were generated. R system was used to classify the segments, which generated a dendrogram and a heat map based on the distance matrix. This made it possible to distinguish three main types and eight subtypes of relief. The morphometric approach used will contribute to a better understanding of the spatial variation in the relief of loess patches.

Digital outcrop modelling using “structure-from- motion” photogrammetry: Acquisition strategies, validation and interpretations to different sedimentary environments

Digital Terrain Model (DTM) or Digital Elevation Model (DEM) is an important data for Raster Analysis in modern GIS. Its use is extremely important for almost all fields of engineering, especially Water Resources Engineering. In Nepal, high-resolution DTM is not available, and often funds are limited to generate high-resolution DTM using modern day technology such as LiDAR or Aerial Photography. As a result most of the works are based on SRTM DEM which is available free of cost. Presently, 1arc second DTM is available in SRTM for Nepalese Territories. In this study, the applicability of 1arc second or 30m resolution SRTM is checked in comparison with the Department of Survey Digital Topographic Map. It is found that SRTM DEM performs better than DEM generated from Data available with Survey Department.Journal of the Institute of Engineering, 2018, 14(1): 235-240