Shadow Cast Tracking for Deduction of Elevation Data Through Affine Matching Methods on Optical Satellite Imagery

Author(s):  
Bas Altena ◽  
Bert Wouters
Water ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 2829
Author(s):  
Jesse N. Beckman ◽  
Joseph W. Long ◽  
Andrea D. Hawkes ◽  
Lynn A. Leonard ◽  
Eman Ghoneim

Over short periods of time, extreme storms can significantly alter barrier island morphology, increasing the vulnerability of coastal habitats and communities relative to future storms. These impacts are complex and the result of interactions between oceanographic conditions and the geomorphic, geological, and ecological characteristics of the island. A 2D XBeach model was developed and compared to observations in order to study these interactions along an undeveloped barrier island near the landfall of Hurricane Florence in 2018. Beachface water levels during the storm were obtained from two cross-shore arrays of pressure sensors for comparison to model hydrodynamics. Aerial drone imagery was used to derive pre-storm and post-storm elevation data in order to quantify spatially varying erosion and overwash. Sediment grain size was measured in multiple locations, and we estimated spatially varying friction by using Sentinel-2 satellite imagery. The high spatial and temporal resolution of satellite imagery provided an efficient method for incorporating pre-storm spatially varying land cover. While previous studies have focused on the use of spatially varying friction, we found that the utilization of local median grain sizes and full directional wave spectra was critical to reproducing observed overwash extent.


Earth ◽  
2022 ◽  
Vol 3 (1) ◽  
pp. 76-92
Author(s):  
David C. Wilson ◽  
Ram K. Deo ◽  
Jennifer Corcoran

We used LiDAR metrics and satellite imagery to examine regeneration on forested sites disturbed via harvest or natural means over a 44-year period. We tested the effectiveness of older low-density LiDAR elevation data in producing information related to existing levels of above ground biomass (AGB). To accomplish this, we paired the elevation data with a time series of wetness and greenness indices derived from Landsat satellite imagery to model changes in AGB for sites experiencing different agents of change. Current AGB was determined from high-density LiDAR acquired in northern Minnesota, USA. We then compared high-density LiDAR-based AGB and estimates modeled using Landsat and low-density LiDAR indices for 10,068 sites. Clear differences were found in standing AGB and accumulation rates between sites disturbed by different agents of change. Biomass accumulation following disturbance appears to decrease rapidly following an initial spike as stands 1asZX respond to newly opened growing space. Harvested sites experienced a roughly six-fold increase in the rate of biomass accumulation compared to sites subjected to stand replacing fire or insect and disease, and a 20% increase in productivity when compared to sites subjected to wind mediated canopy loss. Over time, this resulted in clear differences in standing AGB.


2020 ◽  
Vol 12 (12) ◽  
pp. 2002 ◽  
Author(s):  
Emmanouil Panagiotou ◽  
Georgios Chochlakis ◽  
Lazaros Grammatikopoulos ◽  
Eleni Charou

Generating Digital Elevation Models (DEM) from satellite imagery or other data sources constitutes an essential tool for a plethora of applications and disciplines, ranging from 3D flight planning and simulation, autonomous driving and satellite navigation, such as GPS, to modeling water flow, precision farming and forestry. The task of extracting this 3D geometry from a given surface hitherto requires a combination of appropriately collected corresponding samples and/or specialized equipment, as inferring the elevation from single image data is out of reach for contemporary approaches. On the other hand, Artificial Intelligence (AI) and Machine Learning (ML) algorithms have experienced unprecedented growth in recent years as they can extrapolate rules in a data-driven manner and retrieve convoluted, nonlinear one-to-one mappings, such as an approximate mapping from satellite imagery to DEMs. Therefore, we propose an end-to-end Deep Learning (DL) approach to construct this mapping and to generate an absolute or relative point cloud estimation of a DEM given a single RGB satellite (Sentinel-2 imagery in this work) or drone image. The model has been readily extended to incorporate available information from the non-visible electromagnetic spectrum. Unlike existing methods, we only exploit one image for the production of the elevation data, rendering our approach less restrictive and constrained, but suboptimal compared to them at the same time. Moreover, recent advances in software and hardware allow us to make the inference and the generation extremely fast, even on moderate hardware. We deploy Conditional Generative Adversarial networks (CGAN), which are the state-of-the-art approach to image-to-image translation. We expect our work to serve as a springboard for further development in this field and to foster the integration of such methods in the process of generating, updating and analyzing DEMs.


2016 ◽  
Vol 18 (4) ◽  
pp. 249
Author(s):  
Ely Nurhidayati ◽  
Imam Buchori ◽  
Mussadun Mussadun

Settlements of house on stilts in the Eastern Pontianak is located at the triangle of the Kapuas River and Landak River. This study to determine the changes of settlement’s areas in 2003-2014, predict the settlement’s areas in 2020 and the correlation between the disaster vulnerability and the development of settlement’s areas in the Kapuas riverbanks. This research method integrates quantitative-SIG binary logistic regression and CA-Markov. The data used are Quickbird satellite imagery (2003), elevation data ICONOS (2008) and contour intervals (1 meter). The results are the prediction accuracy (79.74%) and the highest kappa index (0.55). The prediction of settlement’s areas (481.98 hectares) in 2020, shows the highest land expansion in the Parit Mayor Village and the increase of settlement’s areas (6.80 ha/year) in 2014-2020. Regression analysis have a coefficient of 0 in the flooding variable, so the floods did not affected the development of settlement’s areas in the Eastern Pontianak.


2021 ◽  
Vol 13 (21) ◽  
pp. 4245
Author(s):  
Lee B. van Ardenne ◽  
Gail L. Chmura

The determination of rates and stocks of carbon storage in salt marshes, as well as their protection, require that we know where they and their boundaries are. Marsh boundaries are conventionally mapped through recognition of plant communities using aerial photography or satellite imagery. We examined the possibility of substituting the use of 1 m resolution LiDAR-derived digital elevation models (DEMs) and tidal elevations to establish salt marsh upper boundaries on the New Brunswick coasts of the Gulf of St. Lawrence and the Bay of Fundy, testing this method at tidal ranges from ≤2 to ≥4 m. LiDAR-mapped marsh boundaries were verified with high spatial resolution satellite imagery and a subset through field mapping of the upland marsh edge based upon vegetation and soil characteristics, recording the edge location and elevation with a Differential Geographic Positioning System. The results show that the use of high-resolution LiDAR and tidal elevation data can successfully map the upper boundary of salt marshes without the need to first map plant species. The marsh map area resulting from our mapping was ~30% lower than that in the province’s aerial-photograph-based maps. However, the difference was not primarily due to the location of the upper marsh boundaries but more so because of the exclusion of mudflats and large creeks (features that are not valued as carbon sinks) using the LiDAR method that are often mapped as marsh areas in the provincial maps. Despite some minor limitations, the development of DEMs derived from LiDAR can be applied to update and correct existing salt marsh maps along extensive sections of coastlines in less time than required to manually trace from imagery. This is vital information for governments and NGOs seeking to conserve these environments, as accurate mapping of the location and area of these ecosystems is a necessary basis for conservation prioritization indices.


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