scholarly journals EXTRACTION OF ELEMENT AT RISK FOR LANDSLIDES USING REMOTE SENSING METHOD

2018 ◽  
Vol XLII-4/W9 ◽  
pp. 181-188
Author(s):  
R. C. Hasan ◽  
Q. A. Rosle ◽  
M. A. Asmadi ◽  
N. A. Mohd Kamal
Keyword(s):  
At Risk ◽  
Extraction Process ◽  
Automatic Process ◽  
Landslide Risk ◽  
Lidar Data ◽  
Large Area ◽  
Building Footprint ◽  
Element At Risk ◽  
Hazard And Risk ◽  
Study Sites

<p><strong>Abstract.</strong> One of the most critical steps towards landslide risk analysis is the determination of element at risk. Element at risk describes any object that could potentially fail or exposed to hazards during disaster. Without quantification of element at risk information, it is difficult to estimate risk. This paper aims at developing a methodology to extract and quantity element at risk from airborne Light Detection and Ranging (LiDAR) data. The element at risk map produced was then used to construct exposure map which describes the amount of hazard for each element at risk involved. This study presented two study sites at Kundasang and Kota Kinabalu in Sabah with both areas have experienced major earthquake in June 2015. The results show that not all the features can be automatically extracted from the LiDAR data. For example, automatic extraction process could be done for building footprint and building heights, but for others such as roads and vegetation areas, a manual digitization is still needed because of the difficulties to differentiate between these features. In addition to this, there were also difficulties in identifying attribute for each feature, for example to separate between federal roads with state and unpaved roads. Therefore, for large area hazard and risk mapping, the authors suggested that an automatic process should be investigated in the future to reduce time and cost to extract important features from LiDAR data.</p>

scholarly journals Definitions and Concepts for Quantitative Rockfall Hazard and Risk Analysis

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 158
Author(s):  
Didier Hantz ◽  
Jordi Corominas ◽  
Giovanni B. Crosta ◽  
Michel Jaboyedoff
Keyword(s):  
Risk Assessment ◽  
At Risk ◽  
Failure Probability ◽  
Rockfall Hazard ◽  
Process Failure ◽  
Failure Propagation ◽  
Element At Risk ◽  
Hazard And Risk ◽  
Hazard And Risk Assessment ◽  
Definition Of

There is an increasing need for quantitative rockfall hazard and risk assessment that requires a precise definition of the terms and concepts used for this particular type of landslide. This paper suggests using terms that appear to be the most logic and explicit as possible and describes methods to derive some of the main hazards and risk descriptors. The terms and concepts presented concern the rockfall process (failure, propagation, fragmentation, modelling) and the hazard and risk descriptors, distinguishing the cases of localized and diffuse hazards. For a localized hazard, the failure probability of the considered rock compartment in a given period of time has to be assessed, and the probability for a given element at risk to be impacted with a given energy must be derived combining the failure probability, the reach probability, and the exposure of the element. For a diffuse hazard that is characterized by a failure frequency, the number of rockfalls reaching the element at risk per unit of time and with a given energy (passage frequency) can be derived. This frequency is relevant for risk assessment when the element at risk can be damaged several times. If it is not replaced, the probability that it is impacted by at least one rockfall is more relevant.

Semi-Automated Building Footprint Extraction From Orthophotos

GEOMATICA ◽  
2015 ◽  
Vol 69 (2) ◽  
pp. 231-244 ◽  
Author(s):  
Rheannon Brooks ◽  
Trisalyn Nelson ◽  
Krista Amolins ◽  
G. Brent Hall
Keyword(s):  
Image Segmentation ◽  
Best Practice ◽  
Light Detection And Ranging ◽  
Aerial Photographs ◽  
Lidar Data ◽  
Object Based ◽  
Source Data ◽  
Segmentation Approach ◽  
Building Footprint ◽  
Study Sites

Here we describe and apply a semi-automated, object-based method for extracting vector-building footprint polygons from aerial photographs (orthophotos) within urban settings. The approach integrates the use of high resolution orthophotos and image segmentation software and is compared with methods using Light Detection and Ranging (LiDAR) as the source data input. LiDAR data gives the best results with less processing, but is not widely used by municipalities due to the expense. Results from semi-automated image segmentation of the orthophotos showed a high accuracy between extracted building segments and reference building footprints for two study sites, comparable to those achieved using LiDAR data. We recommend image acquisition during summer months with a resolution of 10 cm by 10 cm. When data acquisition budgets are limited, combining ancillary GIS on roads with a semi-automated and object-based segmentation approach is a best practice strategy for land cover feature extraction and change quantification.

GIS-Based Quantitative Landslide Risk Assessment Approach for Property and Life at Bartin Hepler

2021 ◽  
pp. 1623-1636
Author(s):  
Arzu Erener ◽  
Gülcan Sarp ◽  
Şebnem Düzgün
Keyword(s):  
Risk Assessment ◽  
At Risk ◽  
Landslide Risk ◽  
Landslide Occurrence ◽  
Damage Probability ◽  
Landslide Risk Assessment ◽  
Assessment Approach ◽  
Damage Probability Matrix ◽  
Element At Risk ◽  
Work Done

In Turkey, landslides are the second most common natural disasters that cause damages in Turkey that follow the earthquakes. Thus, landslide risk assessment is of crucial importance in this area. Therefore in this study a quantitative approach for mapping landslide risk is developed for property and life at local scale. The approach is first based on the identification of existing elements at risk in the area by the developed algorithm. Then the vulnerability approach focuses on determination of quantitative vulnerability values for each element at risk by considering temporal and spatial impacts by adopting a “damage probability matrix“ approach. The loss estimation was combined with the hazard values which are based on former work done in Bartın Kumluca area where a detailed study of landslide occurrence and hazard in the recent past (last 30 years) was carried out. The final result risk maps for property ($/pixel/year) and life (life/pixel/year) shows all losses per pixel annually for each element at risk in Hepler village.

scholarly journals VULNERABILITY MAPPING AND ANALYSIS: AN IMPLEMENTATION IN GEOHAZARD AREAS IN SABAH

2018 ◽  
Vol XLII-4/W9 ◽  
pp. 189-200 ◽  
Author(s):  
Z. Mohamad ◽  
Z. Ramli ◽  
M. Z. Abd Rahman ◽  
M. R. Mohd Salleh ◽  
Z. Ismail ◽  
...  
Keyword(s):  
At Risk ◽  
Construction Materials ◽  
Weighted Average ◽  
Road Construction ◽  
Risk Mapping ◽  
Vulnerability Mapping ◽  
Natural Phenomenon ◽  
Landslide Risk ◽  
Specific Element ◽  
Element At Risk

<p><strong>Abstract.</strong> Vulnerability identifies the element-at-risk as well as the evaluation of their relationships with the hazard. The relationships relate the landslide potential damages over a specific element-at-risk. Vulnerability can be defined as the degree of loss to a given element-at-risk or set of elements at risk resulting from the occurrence of a natural phenomenon of a given magnitude and expressed on a scale from 0 (no damage) to 1 (total damage). In this study, the landslide vulnerability mapping and analysis were made on two element-at-risks namely buildings and roads. Based on field observations, building and road construction materials have been classified into 22 and 5 construction materials respectively. The field visits were made on specific areas based on candidate buildings and roads as chosen during the landslide exposure analysis and mapping. The vulnerability values for these element-at-risks were expressed using expert opinion. Four experts have been interviewed with separate sessions. The experts were also supplied with local information on the landslides occurrences and photos of element-at-risk in Kundasang and Kota Kinabalu. The vulnerability matrices were combined based on the weighted average approach, in which higher weight was assigned to panel with local expert (landslides and damage assessment), wide experience in landslide vulnerability analysis, hazard and risk mapping. Finally, the vulnerability maps were produced for Kundasang and Kota Kinabalu with spatial resolution of 25<span class="thinspace"></span>cm. These maps were used for the next step i.e. landslide risk mapping and analysis.</p>

scholarly journals Definitions and Concepts for Quantitative Rockfall Hazard and Risk Analysis

2021 ◽  
Author(s):  
Didier Hantz ◽  
Jordi Corominas ◽  
Giovanni B. Crosta ◽  
Michel Jaboyedoff
Keyword(s):  
At Risk ◽  
Failure Probability ◽  
Rockfall Hazard ◽  
Failure Frequency ◽  
Process Failure ◽  
Failure Propagation ◽  
Element At Risk ◽  
Hazard And Risk ◽  
Hazard And Risk Assessment ◽  
Definition Of

There is an increasing need for quantitative rockfall hazard and risk assessment that requires a precise definition of the terms and concepts used for this particular type of landslide. This paper suggests to use terms that appear to be the more logic and explicit as possible, and describes methods to derive some of the main hazard and risk descriptors. The terms and concepts presented concern the rockfall process (failure, propagation, fragmentation, modelling) and the hazard and risk descriptors, distinguishing the cases of localized hazards and diffused hazards. For a localized hazard, the failure probability of the considered rock compartment in a given period of time has to be assessed and the probability for a given element at risk to be impacted with a given energy must be derived combining the failure probability, the propagation probability and the exposure of the element. For a diffuse hazard that is characterized by a failure frequency, the number of rockfalls reaching the element at risk per unit of time and with a given energy (reach frequency) can be derived. However, when the element at risk is not replaced or repaired, the probability that it is impacted by at least one rockfall must be considered.

scholarly journals Application and Validation of a Model for Terrain Slope Estimation Using Space-Borne LiDAR Waveform Data

2018 ◽  
Vol 10 (11) ◽  
pp. 1691 ◽  
Author(s):  
Xuebo Yang ◽  
Cheng Wang ◽  
Sheng Nie ◽  
Xiaohuan Xi ◽  
Zhenyue Hu ◽  
...  
Keyword(s):  
Surface Characteristics ◽  
Airborne Lidar ◽  
Estimation Accuracy ◽  
Estimation Model ◽  
Large Area ◽  
Waveform Data ◽  
Terrain Slope ◽  
Lidar Measurements ◽  
Slope Estimation ◽  
Study Sites

The terrain slope is one of the most important surface characteristics for quantifying the Earth surface processes. Space-borne LiDAR sensors have produced high-accuracy and large-area terrain measurement within the footprint. However, rigorous procedures are required to accurately estimate the terrain slope especially within the large footprint since the estimated slope is likely affected by footprint size, shape, orientation, and terrain aspect. Therefore, based on multiple available datasets, we explored the performance of a proposed terrain slope estimation model over several study sites and various footprint shapes. The terrain slopes were derived from the ICESAT/GLAS waveform data by the proposed method and five other methods in this study. Compared with five other methods, the proposed method considered the influence of footprint shape, orientation, and terrain aspect on the terrain slope estimation. Validation against the airborne LiDAR measurements showed that the proposed method performed better than five other methods (R2 = 0.829, increased by ~0.07, RMSE = 3.596°, reduced by ~0.6°, n = 858). In addition, more statistics indicated that the proposed method significantly improved the terrain slope estimation accuracy in high-relief region (RMSE = 5.180°, reduced by ~1.8°, n = 218) or in the footprint with a great eccentricity (RMSE = 3.421°, reduced by ~1.1°, n = 313). Therefore, from these experiments, we concluded that this terrain slope estimation approach was beneficial for different terrains and various footprint shapes in practice and the improvement of estimated accuracy was distinctly related with the terrain slope and footprint eccentricity.

scholarly journals Joint Monitoring and Analysis of Sea Fog Using Dual Visibility Lidar in Ningbo, China

2021 ◽  
Vol 2112 (1) ◽  
pp. 012014
Author(s):  
Lijun Hu ◽  
Hao Yang ◽  
Hao Wang ◽  
Xinyue Ren
Keyword(s):  
Liquid Water Content ◽  
Lidar Data ◽  
Equivalent Diameter ◽  
Large Area ◽  
Forward Scatter ◽  
Detection Range ◽  
Sea Fog ◽  
Low Visibility ◽  
Joint Monitoring ◽  
532 Nm

Abstract Visibility lidar has obvious monitoring advantages over forward scatter visibility sensors or fog droplet spectrometers; it can measure visibility information over a large area. In 2021, two visibility lidar instruments (1064 or 532 nm wavelengths) were installed in Beilun, Ningbo Zhoushan Port, to monitor sea fog. Comparing their monitoring data to those of forward scatter visibility sensors and a fog droplet spectrometer revealed that the visibility lidar instruments could obtain energy progress information section-by-section in the monitoring path, and could directly reflect sea fog changes. The 1064 nm lidar outperformed the 532 nm lidar regarding sea fog detection. The effective detection range decreased significantly with decreasing visibility; the reliability decreased in low-visibility, uneven atmospheres. In a low-visibility but uniform atmosphere, however, lidar data corresponded well with forward dispersion data. The 532 nm and 1064 nm lidar data sometimes differed at the same monitoring position owing to differing heights and particle reflection angles. During a sea fog event on May 9, 2021, the maximum droplet concentration was 14 cm−3, the maximum liquid water content was 0.21 g·m−3, and the maximum equivalent diameter was 49 μm. The formation of this sea fog was dominated by large particles.

scholarly journals Evaluating the integrity of forested riparian buffers over a large area using LiDAR data and Google Earth Engine

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Hamdi A. Zurqani ◽  
Christopher J. Post ◽  
Elena A. Mikhailova ◽  
Michael P. Cope ◽  
Jeffery S. Allen ◽  
...  
Keyword(s):  
Google Earth ◽  
Riparian Buffers ◽  
Lidar Data ◽  
Large Area ◽  
Google Earth Engine

scholarly journals Extracting Building Boundaries from High Resolution Optical Images and LiDAR Data by Integrating the Convolutional Neural Network and the Active Contour Model

2018 ◽  
Vol 10 (9) ◽  
pp. 1459 ◽  
Author(s):  
Ying Sun ◽  
Xinchang Zhang ◽  
Xiaoyang Zhao ◽  
Qinchuan Xin
Keyword(s):  
High Resolution ◽  
Active Contour ◽  
Active Contour Model ◽  
Remote Sensing Data ◽  
Lidar Data ◽  
Boundary Extraction ◽  
Contour Model ◽  
Optical Images ◽  
Building Footprint ◽  
Salt And Pepper

Identifying and extracting building boundaries from remote sensing data has been one of the hot topics in photogrammetry for decades. The active contour model (ACM) is a robust segmentation method that has been widely used in building boundary extraction, but which often results in biased building boundary extraction due to tree and background mixtures. Although the classification methods can improve this efficiently by separating buildings from other objects, there are often ineluctable salt and pepper artifacts. In this paper, we combine the robust classification convolutional neural networks (CNN) and ACM to overcome the current limitations in algorithms for building boundary extraction. We conduct two types of experiments: the first integrates ACM into the CNN construction progress, whereas the second starts building footprint detection with a CNN and then uses ACM for post processing. Three level assessments conducted demonstrate that the proposed methods could efficiently extract building boundaries in five test scenes from two datasets. The achieved mean accuracies in terms of the F1 score for the first type (and the second type) of the experiment are 96.43 ± 3.34% (95.68 ± 3.22%), 88.60 ± 3.99% (89.06 ± 3.96%), and 91.62 ±1.61% (91.47 ± 2.58%) at the scene, object, and pixel levels, respectively. The combined CNN and ACM solutions were shown to be effective at extracting building boundaries from high-resolution optical images and LiDAR data.

Assessing the impact of mowing on Common Redshanks Tringa totanus breeding on saltmarshes: lessons for conservation management

2017 ◽  
Vol 27 (3) ◽  
pp. 440-453 ◽  
Author(s):  
KLAUS-MICHAEL EXO ◽  
ARNDT H. J. WELLBROCK ◽  
JULIA SONDERMANN ◽  
MARTIN MAIER
Keyword(s):  
At Risk ◽  
Wadden Sea ◽  
Conservation Status ◽  
Habitats Directive ◽  
Positive Effects ◽  
Management Measures ◽  
Favourable Conservation Status ◽  
Study Sites ◽  
The Impact ◽  
Tringa Totanus

SummaryInformed application of habitat management measures is crucial, especially in saltmarshes that function as last refuges for breeding waders in Europe. Despite a reduction in agricultural use of saltmarshes since the establishment of the Wadden Sea National Parks at the end of the 1980s, there remains controversy regarding management measures such as the timing of mowing. We modelled the proportion of nests and chicks that would be jeopardised by mowing at different dates, using long-term breeding data of the Common Redshank Tringa totanus – an endangered and widespread indicator species of saltmarshes – from four study sites in the German Wadden Sea. At two study sites in the western Jadebusen, the proportion of broods that were at risk of being killed when mowing began on 1 July ranged between 78% in early, to 96% in late, breeding years, averaging 87%. Although Common Redshanks in the eastern Jadebusen started breeding one week earlier, the model still predicted a loss of 73% of chicks; while 97% of broods were at risk on the island of Wangerooge. Postponement of mowing to 1 August reduced these proportions to 21%, 11% and 32%, respectively. This study is the first to model the positive effects of delayed mowing of saltmarshes on ground-nesting birds. By implementing adjusted mowing dates in addition to previously suggested reductions in artificial drainage, direct and indirect adverse effects caused by mowing and drainage, such as an increased predation risk, are likely to be reduced, such that a ’favourable conservation status’ according to the EC Habitats Directive may be achieved.

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