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Remote Sensing in Guangzhou area

Lin Shuyu
Institute of Geological Science of Guangdong

Guan Liji
Remote Sensing Centre of ZhongShan University, Guang Zhou China


Abstact
Remote Sensing in Guangzhou area is a big project and covers many subjects of applied techniques. The construction conditions, natural resources, environment, geology and geomorphology in Guang Zhou are has been investigated by means of Aero-remote Sensing method in order to meet the rapid development of the urban area. The results are studied together with previous ground data. We have analyzed some existent problems on the basis of multi-subjects investigation. Meanwhile we have provided various maps to some social departments, and solved many problems in planning small areas and important engineering. The numbers of users of these results are at present more than one hundred. Thus Remote Sensing in Guangzhou area has produced a great influence with its rich results and good effectiveness.

Introduction
In recent years with the rapid economic development, Guangzhou city is facing some serious problems urban expanding, population increasing, farmland decreasing, traffic Jams, lack of power, reconstruction of the city and so on. In order to solve these problems properly, comprehensive scientific data are need to support overall planning. Hereby we have adopted modern technique to collect data as the previous ones are too old and too incomplete to be used. Consequently a bit multi-diplomacy and comprehensive project of remote sensing has been carried out.

Under the leadership of the municipal government, about 15 organizations and 140 technicians, have worked together for more than 2 years and have made a great a achievement. After systematic and scientific study of the results, we have made some suggestions of city construction and management to the related units, thus laying down a solid basis for the establishment of an urban information system.

We must know completely the history, the present status, the future trend of urban factors in order to solve the problems which have popped up in recent years and propose reasonable planning and management. We, in close cooperation with planning -departments, have discussed and expounded 31 monographic items such as urban construction status, natural resources, gology and geomorphology, environmental pollution and remote sensing mapping, etc. According to the requirements of the project, we have carried out color infrared photography (1:20,000), natural color photography (1:10,000) and black/white visible photograph 91:15,000) . The accuracy of every monographic item (including qualitative classification, quantitative statistics and mapping scale) has a good correlation with the specifications set by users and planning departments.

Main rsults and benefits:
  1. The current status of city construction including land use, distributions of architectural density and light, banks use of Pearl River, greenery cover, traffic and urban development were surveyed in detail with Aero-Remote Sensing.

    We classified the land use of Guangzhou into 3 grades and 58 types based on its characteristics and need of city planning and construction. With a plotter A 10 and remote sensing data, the map of land use on scale 1:10,000 was drawn up and the land area of various types was calculated too. We have also analyzed the distributive characteristics, the proportion and other existing problems of land use.

    The Pearl River and its banks within the city are an important area of economic development; we investigated the current status of banks use and found some unreasonable phenomena. Some suggestions to improve administration were made.

    In the past, there was no exact data to show its high population density, high architectural density and serious traffic jams. With the remote sensing images of different dates and scales we have investigated they thus obtained the first completed data. With aero photographs on large scale of different dates we analyzed the Vehicular discharge and density on main streets and drew up their distributive charts. This is the basic data we have provided for the traffic control managements.

    In addition, we have also investigated in detail the greenery quality, type and cover-degree in Guangzhou area, with Remote sensing images on 1:5,000 and provided the information on detailed, systematic and exact greenery status.

    In order to know completely and systematically the construction status of different time, we compiled some maps of land use with aero photographs of 60's, 70's 80's (3 periods).And we compared the quantity, distribution, structural changes of land use in different time, nature and types, These would produce some reliable evidences for overall planning, adjusting development and making a local detailed plan.


  2. In geological and geomorphologic research, 9 results have been achieved by analysing lithosphere properties in the area with remote sensing and ground data. All kinds of rocks, stratigraphic distribution were ascertained and more than 40 exposed, concealed faults were discovered. We slao indicated and predicted various geological perils ----soft soil strata, karst growing area, swelling and shrinking soil areas. Then the city area was divided into different parts based on various geological and engineering conditions. It produces bass for construction, developments and engineering sites. Now these results have been used by more than 40 units.


  3. Natural resource research: 5 results have been gained. The current status quality, quantity and distribution of surface water, land, soil, vegetation, and economic forest and fruit orchards in the area were ascertained.


    4. Water use in the city mainly depends on surface water. The area was divided into 12 parts in two types: hilly area and plain, by means of combining remote sensing data with common ones. After his quality and quality of water sources in all part have been assessed, map of surface water resources compiled. We think that the main problem in water supply is to control water pollution.

    There are plenty of economic forest and fruit resources in Guangzhou and its suburbs. They consist of an important part in urban economic ecosystem. Economic forests and fruit orchards (such as banana pineapple) are divided) are divided into 51 types and the investigation has been conducted. A plan for developing economic forests in urban and suburban areas has been put forward. The investigation and assessment of land resources have been done on the basis of a series of remoter sensing mapping. The land resources of Guangzhou are classified and interpretated in detailed based on the current status of land use and many maps of soil, geomorphology, vegetation, geology as the basic data. Based on the type, nature, characteristics and value, the land resources was divided into 3 degrees, 4 classes and 16 types, thus, providing a basis for city planning and rational use of land. Through the monographic researches of natural resources, a lot of valuable suggestions have been made for current production and constructions, which produce considerable social and economic benefits such as the rational use and protection of water resources, fruit tree planting project, rational utilization of land resources, adjusting the proportion of land use in industry and commerce, full use of wasteland and so on.

  4. Research on urban environment quality: This program covers the pollution of water body, atmosphere and solid wastes, which affect the urban environment quality. Remote Sensing images, especially natural and infrared color images, have been proved to be obviously effective in these fields. Correlative analysis between images and pollution spectral data together with conventional monitoring data measured on the ground at the same time, detailed interpretation has been made to pollution of water body, atmosphere, pollution source and solid wastes. The different pollution factors have been indicated and a mp of various pollution degrees has also been compiled. It is the first time to make clear the degrees and distributions of the pearl River pollution, other water bodies, and atmosphere, the distributions of solid wastes and their influences on environmental quality. A reliable basis is provided to administer urban environment.

    Through interpretation of remote sensing images we have found some pollution sources and their relevant pollution fields which could not be picked out by conventional monitoring methods in the past. It is also possible to trace and monitor the spreading of polluted water mass, which displays clearly in the images.


  5. Remote Sensing mapping: Based on various monographic researches, 27 monographic maps have been compiled and some of them provided for the first time to some relevant departments and offices. These maps have satisfied the urgent needs of urban planning, construction and management in time.

    The initial topographic maps on different scales produced before 70's are hard to meet the demands of planning and management of Guangzhou as the city construction developed too rapidly in the past then years. For this purpose we used the Remote sensing information and the previous status data to modify and compile the urban maps on 1:10,000, 1:12,000 and a:50,000 scales, and compiled black and white image streets, Atlas on 1:50,000 scales. The Remote mpa on 1:20,000 scale and image maps of some areas from 1:500 to 1:500 to 1:500 to scales. The Remote Sensing data has not only met the urgent needs of monographic researches and city management but supplied extensive use to many fields of society. More than 100 units have used these results and great social, economic and environmental benefits have been achieved. In comparison with conventional surveys, the remote sensing has saved 50% funds and 50-80% time.
Conclusion
Generally, a city is a big synthetically system with multiple factors and complex structures. In order to make a good urban planning and management, the collection of basic data must be conducted in time. Conventional measurements require too much time and work to satisfy very urgent needs. This synthetical survey of remote sensing has played its full advantages of high speed, macroscope, high efficiency and it formed multi-subjects investigation and systematic engineering of urban remote sensing. It is helpful for multisubjects to permeate among them and gather scattered data in different units to be processed and applied. At last the results, in the form of detailed classification and accurate data, has become a basis for the scientific planning of city construction. The remote sensing research, with its plenty of results and benefits, has proved to posses a powerful potentiality in urban construction. Remote Sensing as a new techique in information acquisition combined with the application of computers will constitute an important part of an urban information system and play a major role in modernizing urban planning and management.