MAPPING BUILT-UP AREAS USING TWO BAND RATIO ON LANDSAT IMAGERY OF ACCRA IN GHANA FROM 1980 TO 2017


Twumasi N. Y. D. , Shao Z., Altan O.

APPLIED ECOLOGY AND ENVIRONMENTAL RESEARCH, vol.17, no.6, pp.13147-13168, 2019 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 17 Issue: 6
  • Publication Date: 2019
  • Doi Number: 10.15666/aeer/1706_1314713168
  • Title of Journal : APPLIED ECOLOGY AND ENVIRONMENTAL RESEARCH
  • Page Numbers: pp.13147-13168

Abstract

Lack of historical land cover and urban growth governance structure makes spatial planning within the economic capitals of developing countries difficult. Monitoring urban built-up growth with in-situ methods is complicated. In this paper, long-term Landsat archive is utilised to map the built-up areas of Accra, the economic capital of Ghana, in Africa. Simple two band ratio and band combination is coupled with historic Google Earth imagery to monitor built-up dynamics from 1980-2017. A 10-year period was sub-divided into three parts each; early period, mid period and late period for analysis. Maximum Likelihood classifier was used for the classification within the ENVI environment. The results show 11.90% as the highest and 4.63% as the lowest built-up growth rates between 2001-2005 and 1996-2000 respectively. Annual loss of non-built-up areas was 1.31%, and 48.57% over the entire study period. Water bodies lost 0.08% annually but 3.1% over the 37-year period. Highest and lowest overall accuracy were 87.18% and 81.31% respectively, with an average kappa coefficient of 0.7618. Gain in the built-up area was 1676.69 km(2) but non-built up areas lost 1576.10 km(2) while water bodies lost 100.60 km(2). Results will be of interest to spatial planners, policy makers and land administrators.