A METHOD TO ESTIMATE THE LAND USE EFFICIENCY IN THE OLD CITY OF BEIJING
The old city of Beijing represents the brilliant history and attracts people’s attention worldwide. With the rapid development of urbanization in Beijing, the old city is facing the problem that more and more people are working or living in this limited region. How to estimate the land use efficiency in the old city is crucial for the city planners to perform some policy-making decisions. Based on the Sustainable Development Goal 11 (SDG 11) which is to develop inclusive, safe, resilient and sustainable cities and human settlements, in which indicator SDG 11.3.1 is designed to testify the land use efficiency that is defined as a ratio between land consumption rate to population growth rate(PGR).This paper focus on how to evaluate the land use efficiency in the old city where the land is limited to a region while people are in a continuous growing. Based on the extraction of buildings from high resolution images with sub-meter spatial resolution in the area enclosed by the second-ring road which is mainly consists of Dongcheng and Xicheng districts, this study obtained the 3D building information including building height and floor numbers over years from 2005, 2010 to 2015 with the help of visually interpretation, POI information and the in situ investigation. By calculating the ratio of the building density growth rate(BDGR) to the population growth rate, the land use efficiency in the old city was computed for each year. Our results showed that most of the ratios are greater than 1 over year from 2005 to 2010 and less than 1 during periods from 2010 to 2015. Which means that the land use efficiency tend to lower from 2010 to 2015 than from 2005–2010. The reasons caused this phenomenon has been discussed in the discussion part. The results are helpful for local governors or managers to make a better decision in the protection and conservation of the old city, and to keep a sustainable old city.