Abstract: This paper was aimed at developing a three-dimensional approach to evaluate development density using multi-source remote sensing data. The three-dimensional evaluation model of development density is composed of development intensity, development compactness, and development level evaluation. Development intensity is the proportion of built-up areas. Development compactness describes the pattern (fragmented or centralized) of built-up areas. Development level describes the density of economic activities, population and building, and we used economic intensity as its proxy in this paper. We applied this three-dimensional evaluation model to the Pearl River Delta Megalopolis (PRDM), which is one of the most rapidly developing regions in China, and found the following. 1) Rapid urban expansion with the decrease of development compactness was the leading feature of development in PRDM. From 1998 to 2012, the development intensity of the PRDM increased from 8.08% to 16.93%, and the economic intensity increased from 191 million Yuan/km2 to 594 million Yuan/km2, but the development compactness declined from 0.008 2 to 0.006 5, indicating that the spatial form of PRDM tended to be more fragmented. Among the nine cities in PRDM, Shenzhen was the only city whose development compactness increased. Despite PRDM saw a significant increase in economic intensity since 1998, most of the increase should be attributed to the promotion of high land use efficiency of the already existing construction land in 1998. 2) The regional differences in development density were very remarkable. Both evaluation results at town scale as well as 1-km spatial resolution showed that the gaps in development intensity and economic intensity between the inner and outer circles of PRDM were obvious and had been enlarging from 1998 to 2012. In the central area of PRDM, the development intensity exceeded 40% in 2012, while most fringe areas’ development intensities were still less than 10%. The cities were different in economic intensity by a maximum of nearly four times in 2012. 3) The relationship between development intensity and compactness showed a “U” shaped curve at town scale; when the development intensity was less than 40%, the development compactness gradually decreased with the increase of development intensity; when the development intensity passed 40%, it increased fast with the development intensity. Meanwhile the relationship between development intensity and economic density of the towns was not so clear, but showed a roughly rising trend of economic density with the increase of the development intensity. Compared with the traditional method of development evaluation, this three-dimensional approach could synthetically and timely reflect the regional development mode in multi-dimensions using Landsat TM imageries and night-time light data, and could be applied in research at regional scale, city scale, township scale and 1-km spatial resolution. This approach contributes to a more comprehensive analysis of the essential characteristics and temporal-spatial pattern of the regional development mode.

Key words: regional development density, three-dimensional evaluation, night-time light imagery, Landsat TM data, the Pearl River Delta Megalopolis