SOME PROBLEMS OF COMPUTER-ASSISTED MAPPING OF 
LAND USE FROM LANDSAT DATA: THE HONG KONG CASE 
by 
C.P. TO 
Department of Geography and Geology 
University of Hong Kong, HONG KONG 
ABSTRACT 
Land use mapping from Landsat digital data for Hong Kong was carried 
out with the aid of the IBM 3031 computer and the software developed by the 
Office for Remote Sensing of Earth Resources (ORSER) of the Pennsylvania 
State University. The land use maps which were produced with this computer- 
assisted approach included one for the whole of Hong Kong at a scale of 
1:100 000 for 2nd November, 1978 and two for the urban area of Hong Kong at a 
scale of 1:25 000 for 25th December 1973 and 2nd November, 1978. The methods 
of Euclideandistance classification and maximum likelihood classification were 
employed throughout, together with some data preprocessing, such as band 
rationing and canonical transformation. It was found that the accuracy of 
the 1:25 000 urban land use maps showed a much better weighted accuracy (in the 
region of 84 per cent) than that of the 1:100 000 land use map (about 73 per 
cent). It was concluded that proper classifier training rather than the 
choice of different classification methods or the application of data 
preprocessing would determine the accuracy of land use mapping. 
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INTRODUCTION 
In an earlier attempt to evaluate the accuracy of land use mapping of 
Hong Kong, a small territory of 1 061 km“ in area, from Landsat data (Lo, 
1981), it was discovered that the computer-assisted approach could only 
produce a land use map of the urban area at the scale of 1:25 000 with an 
accuracy of 69 per cent. This falls far short of the accuracy reported of 
the 79 to 96 per cent with a 95 per cent level of confidence of the 1:24 000 
scale level II land use maps produced by the United States Geological Survey 
(Fitzpatrick-Lins and Chambers, 1977). A follow-up research was therefore 
conducted to investigate the possibilities of improving the accuracy of 
computer-assisted mapping of land cover/land use of Hong Kong at both small 
and medium scales. Despite Hong Kong's small size, the city-state of five 
million population in 1981 has exhibited a great diversity of urban and rural 
land use patterns. It is also characterised by a hilly but highly broken 
terrain with little flatland. Climatically, Hong Kong experiences distinct 
seasonal changes in weather with a cold, dry winter and a hot, humid summer. 
All these environmental features have made the problem of computer-assisted 
mapping of land use from Landsat data an intricate one for Hong Kong. 
LANDSAT DATA SELECTION 
Hong Kong occupies only the southeast corner of the Landsat scene (Path 
131 Row 44) for the Pearl River Delta. Because of the orbital precession and 
variations in satellite attitude, repetitive overpasses of the satellite 
result in fluctuating coverage of Hong Kong. In most cases, the eastern 
portion is cut off so that the adjacent Landsat scene to its east (i.e. Path 
130 Row 44) obtained in a previous orbit is normally required to make up for 
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