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<front>
<journal-meta>
<journal-id journal-id-type="publisher">ISPRS-Archives</journal-id>
<journal-title-group>
<journal-title>The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences</journal-title>
<abbrev-journal-title abbrev-type="publisher">ISPRS-Archives</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">2194-9034</issn>
<publisher><publisher-name>ISPRS</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/isprsarchives-XXXIX-B6-177-2012</article-id>
<title-group>
<article-title>AN ASSESSMENT OF SHADOW ENHANCED URBAN REMOTE SENSING IMAGERY OF A COMPLEX CITY &amp;ndash; HONG KONG</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Wan</surname>
<given-names>C.-Y.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>King</surname>
<given-names>B. A.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Li</surname>
<given-names>Z.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>The Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University Hung Hom, Kowloon, Hong Kong, China</addr-line>
</aff>
<pub-date pub-type="epub">
<day>27</day>
<month>07</month>
<year>2012</year>
</pub-date>
<volume>XXXIX-B6</volume>
<fpage>177</fpage>
<lpage>182</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2012 C.-Y. Wan et al.</copyright-statement>
<copyright-year>2012</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/3.0/">https://creativecommons.org/licenses/by/3.0/</ext-link></license-p>
</license>
</permissions>
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<abstract>
<p>Large portions of shadowed areas in satellite images of urban areas can affect the accuracy of classification and thus reduce an
image&apos;s effectiveness in urban remote sensing applications. This is particularly acute in cities such as Hong Kong where dense
high-rise buildings cast many long shadows across a variety of different surface types. One solution to this problem is to enhance
shadowed areas so their spectral range becomes closer to their corresponding non-shadowed areas. Shadowed areas were
automatically selected and two techniques, Gamma correction and Linear Correlation Correction, were applied to three study sites of
a 2.4 m Quickbird image. The selected study sites represent typical urban types of Hong Kong, ranging from high-rise commercial to
low-rise residential areas. The shadow detection algorithm is based on the spectral shape index and its limitation is discussed. The
histograms of the corresponding non-shadowed areas, the original and the enhanced shadow areas are used to compare the spectral
range. The results show that the enhanced areas, in band ratios such as NDVI, show greater similarity after enhancement, but they
also look darker than the non-shadowed areas. Where continuous shadowed areas such as in commercial areas, the spectral range
cannot be restored.</p>
</abstract>
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