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Topic 19


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Topic 19

  1. 1. LSGI4321 Essay Chan Tsz Ying Sakina (10595489D)Topic: To facilitate forward planning and development control, planners have beenusing remote sensing techniques to understand the existing land usepattern. However, critiques have argued that “… Despite the promise of new andfast-developing remote sensing technologies, a gap exists between theresearch-focused results offered by the urban remote sensing community and theapplication of these data and products by the governments of urban regions.”(Netzband et al., 2007). Critically assess the validity of the above statementsuggested by Netzband et al. 2007.It is known that remote sensing is applied in many applications. There are manyarticles, journals and books discussing how remote sensing is useful to urbandevelopment. However, Netzband et al. 2007 states that “… Despite the promise ofnew and fast-developing remote sensing technologies, a gap exists between theresearch-focused results offered by the urban remote sensing community and theapplication of these data and products by the governments of urban regions.” Theirview point is quite different from the general cognition towards remote sensingapplication for urban planning. This essay is to critically assess the validity of thestatement. Reasons for validating this statement would be discussed. Also, somerecommendations would be given in order to improve the situation.Generally speaking, the remote sensing data and products are independent,up-to-date and available from anywhere around the earth. Also, the products arereproducible, consistent and comparable (Taubenböck, H. & Dech, S., 2010). Remotesensing technology has many applications. One of the examples is urbandevelopment. Urban development includes urban planning, urban monitoring andland use or land cover type classification. These applications can facilitate thegovernment to analysis the city and make better planning. The government wants toobtain the land use or land cover information in order to analyze the existing landuse situation first before design any plans. This can be achieved by satellite imagesand classification is needed to identify the land cover of each pixels. Remote sensingcan obtain the earth’s image fast and temporally. This can allow change detectionover the same area within a time period. However, is it true that theresearch-focused data and products meet the needs of the regional government forurban development?Urban area is so special that it is a combination of social, economical and naturalarea. Since land resources are limited and valuable, so effective planning is needed inorder to develop the city in accordance with the city characteristics. According to
  2. 2. LSGI4321 Essay Chan Tsz Ying Sakina (10595489D)Wikipedia (2011), urban planning includes ten different aspects, examples are safetyand security, transport and economics. Therefore, the governmental departmentwhich is responsible for urban development needs many different types of data toassist their work. Data like the needs of the citizen, population growth,transportation flow and road network accessibility cannot be provided by remotesensing. It is obvious that the remotely sensed data cannot reveal this kind ofinformation and not applicable in this aspect. This is one of the reasons why there isa gap between research-focused remotely sensed data and government use.More importantly, remote sensing can only provide data. What make the data usefulis how to convert the data into useful information for different end users and fordifferent applications. According to the Steering Committee On Space Applicationsand Commercialization (2001), remote sensing data can initially be complicated andeven irrelevant to potential end users who make policy and management decisions.This kind of users need easily understood information which can be used to addresseconomic, social, environmental, and other policy questions. Obviously, whatNetzband et al. state is due to the fact that the researchers do not really know theneeds of the end users. The end users stated by Netzband are governments of urbanregions. Different cities and regions have different topology, culture and policy. Whatthey need is the information useful for their specific urban development.Different cities have different approaches for urban planning. For example, somecities want to focus on the sustainable development. The cities would like topreserve the agricultural land in the urban fringe. Then, their needs for the data isnot just showing the current urbanization situation, but also the predictions. Theremote sensing community should focus the research on monitoring and predictingthe trend of urbanization in order to provide useful information of the localgovernment to make better plans. This is the reason why remote sensing cannot helpmuch in forward planning. Let’s take one more example. Consider a city which wantsto protect and preserve the ecosystem in urban area. There is a lack of reliable basedata to assess the ecosystem health and biodiversity of many urban cities becauseurban area is too mixed. It is hard to identify the micro ecosystem. Also, remotesensing cannot differentiate the forest, freshwater habitat, natural and semi-naturalgrassland (Borre, J. V. et al., 2010). Remote sensing cannot meet the need ofmonitoring the environmental change due to urbanization. Other technology isneeded rather than remote sensing.Take Hong Kong as another example. Hong Kong is a crowded city with lots of
  3. 3. LSGI4321 Essay Chan Tsz Ying Sakina (10595489D)mountainous area and many people. Shortage of land and housing is a long termproblem in Hong Kong. Town planners need to think of how to explore the new landfor development and preserve the mountain ridge the Victoria Habour view at thesame time. The planning department in Hong Kong needs detail and accurate landuse classification. However, the remote sensing images are limited with more than 2meters per pixel. Still, classification result may not be accurate for a 2-meter pixel. Itis possible to have several land use within a pixel in Hong Kong, especially areas likeSham Shui Po. Remotely sensed data is not very useful to a high density city. Anothersituation is when there is unauthorized development. It is hard for the governmentto sue the owner using satellite image as the evidence because the resolution of theimage is not high enough to identify the building.Another factor causing the remotely sensed data not applicable is the intellectualproperty of the data. Due to the intellectual property right, the cost of purchasingthe data becomes higher. According to Steering Committee on Space Applicationsand Commercialization (2001), there is a growing trend toward licensing rather thanselling commercially produced databases. So the terms for use of the data arecontrolled by the terms of the license. Successive uses of the same data couldbecome very costly. This expense may become a hindrance using remote sensingdata. Moreover, if the government bodies want to share the data to the generalpublic, they may not be allowed because it is possible that the private remotesensing service providers control the number of users. Multiple users may need topay for extra money.Sometimes, the remote sensing data or products cannot meet the need of regionalplanner is due to the fact that remote sensing technology has its limitations. Manyresearchers in the remote sensing field are focusing on how to solve these problemsbecause these limitations would lower the quality of the remote sensing productsand limit the applications. The following would discuss about limitations likerelatively low spatial resolution, cloud cover and shadow problem and atmosphericabsorption.There is always a tradeoff between spatial and spectral resolution of satellites. A highspectral resolution is coupled with a low spatial resolution and vice versa. Forexample, GeoEye-1 is the commercial imaging system launched on September 6,2008 by the U.S. It has the highest spatial resolution compared with similar system atthe moment. It can collect images with a ground resolution of 0.41 meters in thepanchromatic imagery and it collects multispectral imagery at 1.65 meters resolution.
  4. 4. LSGI4321 Essay Chan Tsz Ying Sakina (10595489D)However, it only has four bands including red, blue, green and near infrared in themultispectral imagery (GeoEye-1 Launch Site | About GeoEye-1, 2011). Contrastingly,Earth Observing 1 (EO-1) is a satellite sensor launched on November 21, 2000 by theU.S. It is the hyperspectral sensor with the highest spectral resolution. It contains 220bands but each band has only 30 meters ground resolution (Characterization ofSatellite Remote Sensing Systems | Satellite Imaging Corp, 2011). These twoexamples show that we cannot obtain satellite image with high spatial and spectralresolution at the same time. Although satellite image can provide a relatively largepixel size, this is still not enough for some urban planning application. Take HongKong as an example, Hong Kong’s urban area like Mong Kok, is very crowded withmixed land use. Even 2-meter pixels are hard to classify the land cover type.Cloud cover and shadow is the big problem in optical remote sensing, the problem isespecially serious in the humid tropical region. Clouds would hide the features on theground. Also, its shadow would cast on the ground. If the clouds do not be removedfrom the image, it will affect the result of classification. To mask out the cloud fromthe image, automated cloud masking is used by many researchers. However, simplethresholds cannot handle thin clouds and cloud shadows, and often confuse brightland surfaces as clouds (Li, M. et al., 2003).Beside cloud cover and shadow, atmospheric absorption is another unavoidableproblem for remote sensing. Atmospheric absorption appeared when theatmospheric particles absorb the signal from the satellite. Beside absorption, theatmosphere will reflect, refract and scatter the energy. This problem causes thereflected signal from the features on the ground back to the satellite weaken. Thedigital number (DN) value would be affected. This can be adjusted by atmosphericcorrection. Atmospheric correction is important preprocess of image classification. Ifthe pixel value is not accurate, many analysis works would be affected.It is inevitable that there is a gap between the regional governmental users andresearch-based remote sensing products. Then what should be done is to narrowdown the gap. The following are some suggested solutions.First, the researchers need to understand the need of the government. Regularmeetings or conferences can be held for the two parties in order to understand therecent developments so that they can cooperate with each other. Like Hong Kong,the planning department can cooperate with the Chinese University of Hong Kongand the University of Hong Kong. The Institute of Space and Earth Information
  5. 5. LSGI4321 Essay Chan Tsz Ying Sakina (10595489D)Science from the Chinese University of Hong Kong has the Satellite Remote SensingReceiving Station. The station can capture and process satellite-sourced remotesensing data and provide information that is useful to Hong Kong. On the other hand,the Department of Urban Planning and Design of the University of Hong Kongprovide education of urban planning and design. The planning department canunderstand the academic research directions or area of the institutes and theacademic sides can understand the concerns of the government and the academicresearchers can assist the town planners for better development of Hong Kong.Nothing in the world is perfect. Remote sensing technology has its limitation, but itstill has many advantages that the regional government departments for urbandevelopment can make use of it. Remote sensing can obtain the earth data within alarge area quickly and temporally. Although the spatial resolution is not very high, itcan act as the base information and integrate with different data sources liketopological survey, aerial photographs or overlay with different satellite images foranalysis. This can complement different technologies’ limitation and make thederivative products useful for urban development. Investment by the government isneeded to provide long time training for the technicians, prepare hardware andsoftware and data acquisition. (Steering Committee on Space Applications andCommercialization, 2001)To conclude, it is valid for Netzband et al. (2007) who state that “there is a gapbetween the research-focused results offered by the urban remote sensingcommunity and the application of these data and products by the governments ofurban regions.” The reasons are the lack of understanding and communicationbetween the remote sensing researchers and regional governmental end users. Also,the intellectual property of the remote sensing data may cause the data costly. Thelimitations of remote sensing technology affect the quality of the data and thuslower the effectiveness of these data to urban development application. Whatshould be done is to strengthen the collaboration between the remote sensingcommunity and the governments. Also, the government can try to integrate the dataobtained by different technologies like surveying and photogrammetry with theremote sensed data to derive a more useful data for urban planning.
  6. 6. LSGI4321 Essay Chan Tsz Ying Sakina (10595489D)ReferenceBorre, J. V., Paelinckx, D., Hoffmann, M. Spanhove, T. (2010). Biodiversity MonitoringBeyond 2010: What Role For Remote Sensing?Characterization of Satellite Remote Sensing Systems | Satellite Imaging Corp(2011).Retrieved November 5, 2011 from Launch Site | About GeoEye-1 (2011). Retrieved November 18, 2011 from, M., Liew, S. C. & Kwoh, L. K. (2003). AUTOMATED PRODUCTION OF CLOUD-FREEAND CLOUD SHADOW-FREE IMAGE MOSAICS FROM CLOUDY SATELLITE IMAGERY.Steering Committee on Space Applications and Commercialization (2001).Transforming Remote Sensing Data into Information and ApplicationsTaubenböck, H. & Dech, S. (2010). Remote Sensing and Urban Planning - A CommonFuture?. Retrieved November 19, 2011 from (2011). Retrieved November 18, 2011 from