scholarly journals Change Detection in Coral Reef Environment Using High-Resolution Images: Comparison of Object-Based and Pixel-Based Paradigms

2018 ◽  
Vol 7 (11) ◽  
pp. 441 ◽  
Author(s):  
Zhenjin Zhou ◽  
Lei Ma ◽  
Tengyu Fu ◽  
Ge Zhang ◽  
Mengru Yao ◽  
...  
Keyword(s):  
Coral Reef ◽  
Change Detection ◽  
Accuracy Assessment ◽  
Detection Accuracy ◽  
Reef Environment ◽  
Object Based ◽  
Coral Reef Environment ◽  
Study Sites ◽  
Object Area ◽  
Segmentation Image

Despite increases in the spatial resolution of satellite imagery prompting interest in object-based image analysis, few studies have used object-based methods for monitoring changes in coral reefs. This study proposes a high accuracy object-based change detection (OBCD) method intended for coral reef environment, which uses QuickBird and WorldView-2 images. The proposed methodological framework includes image fusion, multi-temporal image segmentation, image differencing, random forests models, and object-area-based accuracy assessment. For validation, we applied the method to images of four coral reef study sites in the South China Sea. We compared the proposed OBCD method with a conventional pixel-based change detection (PBCD) method by implementing both methods under the same conditions. The average overall accuracy of OBCD exceeded 90%, which was approximately 20% higher than PBCD. The OBCD method was free from salt-and-pepper effects and was less prone to images misregistration in terms of change detection accuracy and mapping results. The object-area-based accuracy assessment reached a higher overall accuracy and per-class accuracy than the object-number-based and pixel-number-based accuracy assessment.

scholarly journals Evaluating the feasibility and advantage of a multi-purpose submerged breakwater for harbor protection and benthic habitat enhancement at Kahului Commercial Harbor, Hawai‘i: case study

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Yuko Stender ◽  
Michael Foley ◽  
Ku’ulei Rodgers ◽  
Paul Jokiel ◽  
Amarjit Singh
Keyword(s):  
Coral Reef ◽  
Coral Cover ◽  
Ecological Impact ◽  
Coastal Protection ◽  
Benthic Habitat ◽  
Engineering Structures ◽  
Camera System ◽  
Reef Environment ◽  
Submerged Breakwater ◽  
Coral Reef Environment

AbstractConstruction of breakwaters provides an engineering solution for coastal protection. However, little effort has been made toward understanding the ecological impact on local coral reef ecosystems and developing engineering structures that would enhance the coral reef environment. A submerged breakwater proposed for Kahului Commercial Harbor, Hawai‘i, provided an opportunity to design a multi-purpose ‘reef structure’ to mitigate wave impacts while providing new coral reef habitat. This design involved ecological and environmental considerations alongside engineering principles, serving as a model for environmentally sound harbor development. This field study evaluated environmental conditions and reef community composition at the proposed site in a gradient extending outward from the harbor, using in situ data with multivariate analyses. Benthic and topographic features in the area were assessed using a towed drop camera system to relate to biological factors. Results that support breakwater topography should follow the natural spur and groove and depth of the adjacent reef and orient with wave direction. A deep area characterized by unconsolidated substrata and low coral cover would be replaced with the shallow, sloping hard bottom of the breakwater, and provide an exemplary area for corals to flourish while protecting the harbor from large ocean swells. Surfaces on shallow sloping hard bottoms receive higher levels of irradiance that benefits coral growth. Optimal levels of water motion facilitate sediment removal and promote coral recruitment and growth. The design of the Kahului Harbor submerged multi-purpose structure serves as a model for design of shoreline modification that enhances, rather than degrades, the local coral reef environment.

Estimation of Sand Distribution in Coral Reef Environment using Colour Segmentation and Colour Thresholding Methods

2019 ◽  
Vol 1 (3) ◽  
pp. 96-104
Author(s):  
Pauleen Ong ◽  
Muhammad Suzuri Hitam ◽  
Zainuddin Bachok ◽  
Mohd Safuan Che Din
Keyword(s):  
Coral Reef ◽  
Extraction Methods ◽  
Colour Difference ◽  
Reef Environment ◽  
Still Images ◽  
Point Count ◽  
Automatic Computer ◽  
Computer Based ◽  
Coral Reef Environment ◽  
Colour Segmentation

At present, marine scientists employ manual method to estimate the components in coral reef environment, where Coral Point Count with Excel extensions (CPCe) software is used to determine the coral reef components and substrate coverage. This manual process is laborious and time consuming, and needs experts to conduct the survey. In this paper, a prototype for estimating the distribution of sand cover in coral reef environment from still images by using colour extraction methods was introduced. The colour segmentation called delta E was used to calculate the colour difference between two colour samples. Another method used was colour threshold by setting the range of sand colour pixels. The system was developed by using a MATLAB software with image processing toolbox. The developed system was semi-automatic computer-based system that can be used by researchers even with little knowledge and experience to estimate the percentage of sand coverage in coral reef still images.

scholarly journals IMPACT OF OFFSHORE SAND MINING ON SANDY BEACH IN CORAL REEF ENVIRONMENT - CASE STUDY IN KINENHAMA BEACH, TOKUNOSHIMA ISLAND, JAPAN

2015 ◽  
Vol 71 (2) ◽  
pp. I_772-I_777
Author(s):  
Ryuichiro NISHI ◽  
Yoshihisa TSURUNARI ◽  
Kazunori HOSOTANI ◽  
Mario de Leon ◽  
Isao MATSUMOTO ◽  
...  
Keyword(s):  
Coral Reef ◽  
Sandy Beach ◽  
Sand Mining ◽  
Reef Environment ◽  
Coral Reef Environment

Multiple Factors driving Variability of CO2 Exchange Between the Ocean and Atmosphere in a Tropical Coral Reef Environment

2012 ◽  
Vol 18 (4) ◽  
pp. 357-386 ◽  
Author(s):  
Rachel F. S. Massaro ◽  
Eric Heinen De Carlo ◽  
Patrick S. Drupp ◽  
Fred T. Mackenzie ◽  
Stacy Maenner Jones ◽  
...  
Keyword(s):  
Coral Reef ◽  
Co2 Exchange ◽  
Reef Environment ◽  
Multiple Factors ◽  
Tropical Coral ◽  
Coral Reef Environment ◽  
Tropical Coral Reef

Conventional tagging and acoustic telemetry of a small surgeonfish, Zebrasoma flavescens, in a structurally complex coral reef environment

2011 ◽  
Vol 91 (2) ◽  
pp. 185-201 ◽  
Author(s):  
Jeremy T. Claisse ◽  
Timothy B. Clark ◽  
Brett D. Schumacher ◽  
Sarah A. McTee ◽  
Megan E. Bushnell ◽  
...  
Keyword(s):  
Coral Reef ◽  
Acoustic Telemetry ◽  
Reef Environment ◽  
Coral Reef Environment

scholarly journals A supervised method for object-based 3D building change detection on aerial stereo images

2014 ◽  
Vol XL-3 ◽  
pp. 259-264 ◽  
Author(s):  
R. Qin ◽  
A. Gruen
Keyword(s):  
Change Detection ◽  
Current Trend ◽  
Detection Methods ◽  
Support Vector ◽  
Detection Accuracy ◽  
Status Change ◽  
Aerial Photos ◽  
Object Based ◽  
The Status

There is a great demand for studying the changes of buildings over time. The current trend for building change detection combines the orthophoto and DSM (Digital Surface Models). The pixel-based change detection methods are very sensitive to the quality of the images and DSMs, while the object-based methods are more robust towards these problems. In this paper, we propose a supervised method for building change detection. After a segment-based SVM (Support Vector Machine) classification with features extracted from the orthophoto and DSM, we focus on the detection of the building changes of different periods by measuring their height and texture differences, as well as their shapes. A decision tree analysis is used to assess the probability of change for each building segment and the traffic lighting system is used to indicate the status "change", "non-change" and "uncertain change" for building segments. The proposed method is applied to scanned aerial photos of the city of Zurich in 2002 and 2007, and the results have demonstrated that our method is able to achieve high detection accuracy.

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