2009 Urban Remote Sensing Joint Event
A Review of Remote Sensing Applications in Urban Planning and Management in China Yinghui Xiao
Qingming Zhan
School of Urban Design Wuhan University Wuhan 430072, China
[email protected]
School of Urban Design Wuhan University Wuhan 430072, China
[email protected]
Abstract - It is well-known that remote sensing technology has played a very important role in the urban planning and management since 1980s. In the past thirty years, as one of spatial data sources, remote sensing datasets, which contain more information of earth surface as compared with usual urban maps, have been used in urban planning and management in China. With the development of remote sensing technology such as the high spatial resolution sensors, 3D laser scanning, data mining and advanced image processing technology, remote sensing can be widely used in the whole range of urban planning processes. In this paper, we firstly make a review of the urban remote sensing applications in urban study and planning by giving examples. Then we identify remote sensing applications in different urban planning stages including master planning, district planning, detailed planning and planning implementation as well as in urban studies. We also analyze the bottlenecks of the remote sensing applications in urban planning and management in China at the end. I.
INTRODUCTION
Urban planning is generally understood as activities to prepare development plans to regulate and control the use of spaces in cities. Its main objective is to improve living conditions of urban areas and the welfare of urban residents. As an important tool for the public decision making of local governments, urban planning has played a key role in rapid urbanization and economic development over the past thirty years in China. Urban planning has to be supported by various types of knowledge. Knowledge depends upon information and information extraction based on the processing of data. In order to identify the existing problems and the needs and to have a comprehensive understanding of the interacting elements and their effects , urban planners have to acquire a wide range of information and are capable of using tools and techniques to analyze those information. Planners usually collect planning information by field visiting, review the historical documentsexisting topographic
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maps and so on. It is considered time consuming and labor intensive. Remote Sensing (RS) is a technique of collecting data from a distance without touching the objects. Broadly defined, remote sensing is not limited to digital, satellite-based sensor systems, but encompassed the realm of photogrammetric and hence conventional analogue sensors, including aerial photography. Viewed from this perspective, remote sensing has been used routinely to provide information on urban areas for analysis and planning purposes in the last three decades. For instance, analogue ortho-photos have long been used in urban planning. Now the satellite imagery owns its position in the urban planning applications by taking the advantages of easy to access, less expansive in contrasting with conventional aerial photographs, easy for time sequence comparison and etc. Remote sensing has long been widely used in resource inventory, land use change monitoring and many other applications. In urban planning, first of all, remote sensing is regarded as an important data source for monitoring of urban expansion and land use change analysis. With the interpretation (visual or computer based) of remotely sensed imagery, urban planners can get the land use data, which play an important role in urban planning processes. Secondly, remote sensing can be applied to the monitoring of the urban environment concerning air and water pollutions, green space investigation. Remote sensing is also used in the urban traffic analysis and other aspects of urban studies. With the development of the remote sensing technology such as increasing of spatial land spectral resolution, three dimensional (3D) laser scanning, data mining, advanced image processing technology, remote sensing is expected to be widely used in the whole procedure of urban planning. The following sections of this paper explore the effectiveness of remote sensing as contributed to the applications in urban planning and management. II.
REMOTE SENSING APPLICATIONS IN URBAN STUDY
In general, the planning process is the decision-making process. In order to better understand the current situation and trajectory of urban development, urban study is indispensable and essential. In 1980s, remote sensing technology was introduced into the urban study and the scope of planners in China.
2009 Urban Remote Sensing Joint Event The well-known case of applying remote sensing in urban study was the so called 8301 project implemented in Beijing in 1983. This project used airborne remote sensing technology to acquire large amount of essential information about soil and water resource utilization, environmental geology, environmental pollution, ecological conditions, heat island effect, green space, transportation, urban construction in Beijing. It also provided the accurate data of urban land use, green coverage, garbage dumping sites, and distribution of chimney in Beijing built up areas. Such useful information provided a scientific basis for urban planning and development study of Beijing [21]. Shangshai has been taken three rounds of urban survey by using remote sensing approach since 1988, which provide large amount essential information for urban land use planning, urban redevelopment, etc. [26] The Ministry of Land and Resources of China initiated a key project called “National Landuse Dynamic Monitoring Based on the Remote Sensing” in 1999. The aim of this project is to monitor the land use and land cover changes of 66 big cites (cities with population over 500 thousands) based on satellite imagery such as Landsat TM, SPOT MSS and China made systems . The results of this project have been applied to the investigation of land and resources, protection of arable land, implementation inspection of land use planning and enforcement of the law land administration, land use management, and inspection of the reliability of various land related statistical data. It provides reliable information to support land administration at the national level as well as the local level. Figure 1 shows a practical example.
Original TM image, 1998
Rectified TM image,1998
Rectified SPOT image 1999
Fused image 98+99
Fused image 1999
Change detection
for short-term construction (the Explanatory Notes of the City Planning Act, chapter 2, article 13,14, and 15). The main contents of master planning include: Specifying directions of future urban expansion and the land use structure; Preparing the structure and layout of the urban transportation system; Arranging development of water and green system; Preparing special protection plans if the city is on the list of the cultural and historical cities. The master planning is a complicated periodic work and required a wide range of essential information that have to be collected partially by means of remote sensing. With the advantages of large area coverage (e.g.; the coverage size of one scene of Landsat TM image covers an area of 185 km by185 km)informative (multi temporal, multi spectral, etc.)all-weather (micro wave RS images) and cost-effective, remote sensing is very helpful to the investigation and analysis of city’s natural conditions, resource distribution, geographical layout of towns, road network, urban expansion and land use change. Some examples are given in the remaining parts of this section. A. Spatial and temporal analysis of urban expansion and landuse change One of the important contents of the master planning is to determine the scale of urban development in the future. It is essential to understand how the city grows dynamically in the past. Therefore, the analysis of urban expansion based on remote sensing images has becoming a basic task of the urban master planning in China. One example is presented in Figure 2 where the built up areas were derived mainly from satellite images and aerial photographs acquired at different periods of time [18].
Statistical table
Interpretation result
Figure 1. Landuse change monitoring III.
REMOTE SENSING APPLIED FOR URBAN MASTER PLANNING
The urban master planning plays a very important role in urban planning in China. According to the City Planning Act: “the urban master plan should include the designated function of a city, the development goal and target planning size of the city, the standards, norms and criteria for the main constructions in the city and the land use structure, functional and land use differentiation and the general layout for various types of construction, comprehensive transport system, water space and green space system, district planning and planning
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Figure 2. Urban expansion in Wuhan city Source: Zhan et al, 2009 Remotely sensed data have played an important role in detecting urban morphologies effectively since 1980s in China. Nowadays a wide range of sensors are available that provide the panchromatic, multispectral as well as SAR and LIDAR data by different platforms, such as Landsat, SPOT, IKONOS, Quickbird, Radarsat and so on. In general, medium and low spatial resolution image such as Landsat (with 15 – 30 m spatial resolution) and medium high spatial resolution such as SPOT 4 images (with 10 – 20 m spatial resolution) can be used to describe the spatial and
2009 Urban Remote Sensing Joint Event temporal patterns of urban sprawl. The high resolution images such as IKONOS, Quickbird, and SPOT 5 are needed concerning the detailed land use changes in the inner city. B. Conservation planning of cultural heritages and historic sites To fully understand a historical heritage before protecting or rebuilding it, accurate documentation and 3D visualization play essential role in protection of historical sites. Due to its high historical value, it is important to measure and model a historical site including many ancient buildings with relatively high accuracy. Besides many conventional sensor images and applications in the planning practice, newly developed sensors such as airborne laser scanning (ALS) and terrestrial laser scanning (TLS) are also considered very useful in planning applications. In recent year, both ALS and TLS have become popular data acquisition tools since they can provide high precision 3D data. 3D modeling is a very useful tool for better communication and understanding of cultural heritages and historical sites as well as historical districts. Laser scanners offer fascinating possibilities for measuring millions of points within a short period of time. Some of them have been integrated with a digital camera to capture color images at the same time. Thus, is possible to record complete 3D objects such as cultural heritages and historical sites efficiently and accurately. Figure 3 shows an example of San Fan Qi Xiang district and the Temple of Confucian Learning in Fuzhou, Fujian province.
Figure 3 3D Laser Scanning of San Fan Qi Xiang historical neighborhood (left) and Temple of Confucian Learning (right) in Fuzhou City Source: (Xiao et al, 2007) C. Basemap for urban master planning The topographic maps have long been used as base maps for urban master planning. However, the traditional topographic maps do not reflect the real situation especially in urban areas since they are main produced by conventional cartographic technologies which are time-consuming and labor-intensive. Much useful information is missing in these maps due to the generalization and aggregation steps in map production. For example, the line graphic map can hardly describe the height and type of complex buildings, cloverleaf intersection, the city sculpture, and so on. So it could not fully satisfy the information demands of urban planners. Remote sensing data provide luxuriant information of earth surface. It can factually and objectively reflect the status of terrain surface, man-made objects, phenomena, environmental
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and ecological indicators and even human activities at the recording moment. So it has incomparable advantages to use remote sensing images as the base map of urban master planning as compared with the use of traditional topographic maps. Image based planning maps and electronic sand tables have enhanced the ability for illustration of contents of master planning. Therefore remote sensing and it by products have been used in public participation and the decision making processing of the municipal governments. IV.
REMOTE SENSING APPLIED FOR DETAILED PLANNING
According to the Chinese urban planning system, detailed planning is to arrange the detailed land use layout, basic service, and spatial structure of specific areas with the guidance of the urban master plan and district plan. It can be divided into two categories: regulatory planning and site planning. Regulatory planning is to specify a number of indicators for the building control such as land use functions and development intensity, roads and pipelines, etc. Site planning is to provide more detailed design of the specific construction projects. In compare to the urban master planning, detailed planning is concerning with more detailed arrangement at the ground. Therefore high spatial resolution images are required in order to meet the requirement of urban detailed planning. After the launching of the high resolution commercial satellites such as IKONOS 10 years agosatellite remote sensing data (which is cheaper and easier to acquiring than airborne remote sensing images) have started to contribute to the detailed planning. The required detailed data such as individual buildings roads and footpaths, detailed land use information can be derived from high resolution satellite imagery. It is of great significance to the urban planning especially to the detailed planning. Furthermore, new sensor 3D laser scanners have been invented and put into operation. In urban detailed planning stage, remote sensing data can be applied to extraction of building density and floor area ratio, calculation of the minimum distance between the adjacent buildings to avoid being hidden from sunlight. The high spatial resolution images (IKONOS and Quickbird), which with the stereovision capability and three dimensional laser scanning data are very useful to the terrain analysis as well as building three dimensional city models. Moreover, remote sensing data can be useful as well to the urban design such as analysis of city skyline and profiles of high rise buildings. V.
REEMOTE SENSING DATA APPLIED FOR PLANNING MANAGEMENT
Urban planning management or administration is comprised in various steps of the whole planning process. In this section, we focus on two contributions of remote sensing data. One is the monitoring of planning effectiveness. Another one is the identification of illegal development. Both are the important routine works of planning management in China. A. Monitoring the effectiveness of approved plans Planning implementation is an important stage of the planning process. Monitoring and examining the adopted
2009 Urban Remote Sensing Joint Event plans in terms of its effectiveness is essential and useful. But lack of scientific analysis methods for quantitative evaluation stems this stage of planning processes in the past. Fortunately, remote sensing can provide up to date and real-time images which can meet the demands of above mentioned requirement. The method is to compare the planning data and image data to find out the differences between them by using the overlay function of GIS. Digital maps of both plan and reality are preferred for this analysis. Figure 3 shows an example of this kind of analysis in Wuhan city.
For the inspection of illegal urban development, there are lots of successful cases available in many Chinese cities. Figure 5 shows an example of Beijing.
Figure 5 An example of change detection and analysis based on satellite images of Beijing Source: (Zhang et al, 2006) VI.
Figure 4 Evaluation of planning implantation Source: (Xiao, 2002) B. Identifying illegal development China is in a rapid urban development process. It is inevitable the arising of the development without official approval by the local government. These illegal developments affect the city’s landscape and set back the development of the city. Supervision and inspection the illegal development has become the routine task of urban planning and development control in China. The traditional approach for those inspections often requires a large number of inspectors. The high resolution images such as IKONOS images (1.0m), Quickbird images (0.65m) are needed, since individual buildings have to be identified in the images. Both manual and automatic change detection technologies can be applied in the identification of illegal development. Change detection need images obtained at two different time periods. After the geo-referencing or coregistration of two images, the differences can be detected and analyzed.
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THE BOTTLENECKS OF THE APPLICATIONS
There are some bottlenecks of the remote sensing applications existed in urban planning and management in China. The data requirement of urban planning is much broader than that remote sensing could provide since the limitations of the spatial, temporal and spectral resolution. Two main factors that affect the remote sensing applications in urban planning can be identified. The first one is the limitation of the existing remote sensing technique such as the spatial, temporal and spectral resolution, image processing technology, and object recognition and information extraction technology. The second factor is concerning the human factor. Urban planning and remote sensing technology are treated as two different disciplines. In the field of urban planning, many planners lack of the knowledge of using remote sensing technologies. On the other hand, many remote sensing experts do not really understand the data requirement from the planning practice. At present, urban planners have to rely on remote sensing experts that might cause misunderstanding between them. VII. CONCLUSIONS Applications of remote sensing in urban planning and management have drawn great attention from time to time. On the one hand, remote sensing as an important data source provides enriched and up to date information for planning at the different planning levels. On the other hand, remote sensing plays important role in monographic study in urban areas such as dynamic monitoring of urban sprawl, land use change analysis, infrastructure network (roads, railways and settlements) study, hydrological features (river/stream, lakes)
2009 Urban Remote Sensing Joint Event extraction, urban environment monitoring, etc. it is wellknown that planning at the different levels required information about cities with different scales and at different detailed levels (e.g. 1:10,000-1:25,000 for master planning, 1:1000-1:2000 for detailed planning). Recent developments in term of higher spatial resolution, higher spectral resolution as well as higher temporal resolution have provided wider range of application potentials in urban planning and management. Airborne LIDAR and terrestrial laser scanning have shown a bright future for applications in urban areas.
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ACKNOWLEDGMENT This research is supported by the Hi-Tec Research and Development Project (863 project, No. 2006AA12Z151) and the National Natural Science Foundation of China (No. 40871211).
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