Object-based classification of Ikonos imagery for mapping large-scale vegetation communities in urban areas

Mathieu, Renaud and Aryal, Jagannath and Chong, Albert K. (2007) Object-based classification of Ikonos imagery for mapping large-scale vegetation communities in urban areas. Sensors, 7 (11). pp. 2860-2880. ISSN 1424-8220

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Effective assessment of biodiversity in cities requires detailed vegetation maps. To date, most remote sensing of urban vegetation has focused on thematically coarse landcover products. Detailed habitat maps are created by manual interpretation of aerial photographs, but this is time consuming and costly at large scale. To address this issue, we tested the effectiveness of object-based classifications that use automated image segmentation to extract meaningful ground features from imagery. We applied these techniques to very high resolution multispectral Ikonos images to produce vegetation community maps in Dunedin City, New Zealand. An Ikonos image was orthorectified and a multi-scale segmentation algorithm used to produce a hierarchical network of image objects. The upper level included four coarse strata: industrial/commercial (commercial buildings),residential (houses and backyard private gardens), vegetation (vegetation patches larger than0.8/1ha), and water. We focused on the vegetation stratum that was segmented at more detailed level to extract and classify fifteen classes of vegetation communities. The first classification yielded a moderate overall classification accuracy (64%, κ = 0.52), which led us to consider a simplified classification with ten vegetation classes. The overall classification accuracy from the simplified classification was 77% with a κ value close to the excellent range (κ = 0.74). These results compared favourably with similar studies in other environments. We conclude that this approach does not provide maps as detailed as those produced by manually interpreting aerial photographs, but it can still extract ecologically significant classes. It is an efficient way to generate accurate and detailed maps in significantly shorter time. The final map accuracy could be improved by integrating segmentation, automated and manual classification in the mapping process, especially when considering important vegetation classes with limited spectral contrast.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Reproduction is permitted for noncommercial purposes. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/). This article belongs to the Special Issue 'Sensors for Urban Environmental Monitoring'.
Faculty / Department / School: Historic - Faculty of Engineering and Surveying - Department of Surveying and Land Information
Date Deposited: 09 Apr 2010 12:37
Last Modified: 30 Jul 2013 05:07
Uncontrolled Keywords: object-based classification; remote sensing; cities; New Zealand; biodiversity; habitat
Fields of Research : 09 Engineering > 0909 Geomatic Engineering > 090999 Geomatic Engineering not elsewhere classified
05 Environmental Sciences > 0502 Environmental Science and Management > 050206 Environmental Monitoring
08 Information and Computing Sciences > 0801 Artificial Intelligence and Image Processing > 080106 Image Processing
Socio-Economic Objective: D Environment > 96 Environment > 9606 Environmental and Natural Resource Evaluation > 960610 Urban Land Evaluation
Identification Number or DOI: 10.3390/s7112860
URI: http://eprints.usq.edu.au/id/eprint/7337

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