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26 Jul 2017

Case Study: Use of Satellite Imagery in the Classification of Mangrove Species

In support of UNESCO's International Day for the Conservation of the Mangrove Ecosystem today, Geoimage presents this case study on the Classification of Mangrove Species: Application of Earth Observation satellite imagery in the monitoring and conservation of Mangroves.

Project Overview

This case study utilising WorldView-3 imagery showcases a robust, non-invasive, cost-effective, reproducible, consistent and un-biased strategy to monitor and preserve the very fragile and important environments that are mangrove habitats.

 Challenge: Provide an indication of rehabilitation success of an adjacent mangrove habitat, potential impacts to nearby mangrove forests and comparison to control sites growing within the same region.
 Scope: 
Mapping and analysis of plant groups at species level. 
 Method: Use archived imagery collected by the WorldView-3 satellite in 8 discrete wavelength bands at 2m resolution and one broad wavelength band at 50cm resolution.  
 Location: Four discrete mangrove habitats within a 50sq km area were investigated.
 Outcome:
Reduced the need for extensive, lengthy and expensive field visits.
Un-biased and stable dataset allowed our client to limit the number of training and calibration sites required for consistent mangrove monitoring.
Minimizing operational costs, the application of remote sensing technology reduced the need for associated health and safety considerations and minimized the potential for injury and lost time.

Detailed Case study 

This case study is the Classification of Mangrove Species by Geoimage, wherein we demonstrate how Earth Observation Satellite imagery can support and protect one of the world’s most fragile and important ecosystems.

Earth Observation satellites have been collecting imagery since the launch of ERTS-1, renamed Landsat 1, in 1972 and hence, there is a significant archive of imagery for many applications, including visual inspection and interpretation, analysis, extraction of information, change detection and land cover classification.  Since the launch of the first very high resolution (sub-metre) sensor in 1999, Geoimage has had the ability to apply these types of investigations at a much higher detail, such as mapping and analysis of plant groups at species level. 

The project described herein uses archived imagery collected by the WorldView-3 satellite in 8 discrete wavelength bands at 2m resolution and one broad wavelength band at 50cm resolution. 

Background

Many industrial and commercial businesses that adjoin mangroves, particularly where damage has occurred, have a regulatory requirement to offset (by coordinated planting), rehabilitate and monitor these environments. 

This project was undertaken to provide an indication of rehabilitation success of an adjacent mangrove habitat, potential impacts to nearby mangrove forests and comparison to control sites growing within the same region.  The rehabilitation process involved the planting and monitoring of two mangrove species i.e. Rhizophora stylosa and Avicennia marina. 

The described application of remotely sensed satellite imagery and analysis of same provided several advantages compared to that of ground based monitoring investigations and can be considered as a useful tool in the characterization, assessment of environmental impacts and ultimately the preservation of mangrove forests, whether these be naturally occurring or planted. 

Benefits to the environment 

Mangroves are an important part of estuarine ecosystems and wetlands and are protected in many Australian jurisdictions.  Specifically, under Queensland legislation all marine plants (including mangroves) are protected under the Fisheries Act 1994.  This act prohibits the destruction, damage or disturbance of marine plants without approval from the regulator.  

Due to the importance of mangroves, monitoring is an important means of characterisation allowing determination of composition, health and distribution of forests.  This information can be used to compare status and identify trends and provide information useful in environmental impact assessments.

Application of emerging or developing technologies

The application of remote sensing for monitoring mangroves has significant advantages to that of traditional manual surveys. 

Information can be gathered in a non-invasive manner and provides greater objectivity (the data is quantitative) by removing subjectivity of assessors on the ground. In addition, remote sensing techniques have a great potential for reproducibility and consistency across discrete and adjacent areas of investigation. Satellite imagery is also able to cover greater spatial areas, removing sizable coordination and costs associated with labour intensive manual surveys.

Unlike traditional surveys, sensors such as WorldView-3 collect information in wavelength ranges of the electromagnetic spectrum that lie outside of the visible range. The discrete spectral responses of the 8 bands on WorldView-3 to different land cover types allows a more robust classification and provide a greater sensitivity to the mangrove species varieties.  In addition, the near infrared bands can be used to provide insight into vegetation attributes such as plant health or vigour, which may also be used in the classification criteria. 

Whilst not unique in its application for scientific studies and similar selected applications, WorldView-3 8 band imagery provides great potential in mainstream markets for environmental monitoring through a combination of high spatial resolution and spectral capability.  This allows for greater differentiation of features for purposes of identification, classification and improved characterisation.  

Finally, the availability of an extensive data archive allows for the investigation of temporal changes and trends over a regional or localized landscape and potentially further calibration and qualification of results.

Contact Geoimage to learn more 

At Geoimage we believe that Earth Observation satellite imagery is an extremely useful and cost effective tool to Environment and Sustainability applications. 

To learn more about this case study and the benefits of innovative imaging solutions in environmental monitoring, please contact Geoimage on 07 3319 4990.

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