Geoscience Reference
In-Depth Information
and Fleer
1998
; Huttner and Bruse
2009
). Thanks to its almost contiguous spectral
coverage between 450 and 2,500 nm (Cocks et al.
1998
) as well as its high spatial
resolution, HyMap imagery was well suited to discriminate between different urban
surface materials having distinct reflection and absorption features across its entire
spectral range (cf. Heiden et al.
2007
;Heroldetal.
2007
;Frankeetal.
2009
).
In conjunction with the object heights extracted from HRSC data, hyperspectral
remote sensing and its derivative products enabled providing the spatial information
required for urban microclimate modeling with ENVI-met (Heldens
2010
; Heldens
et al.
2010
,
2012
).
The present work aims at evaluating the potential of airborne hyperspectral
data and LiDAR-derived object heights for urban surface material mapping and
microclimate modeling. In contrast to previous studies, the hyperspectral data cover
a much smaller spectral range (380-1,050 nm, Itres Research Ltd.
2013
), which
complicates the detection of surface materials having spectral key features occurring
only at longer wavelengths (e.g., in the short-wave infrared domain; Heiden et al.
2007
;Heroldetal.
2007
). A dedicated approach for the fusion of the above datasets
is presented, and the achieved mapping and modeling results are described and
discussed accordingly.
11.3
Materials
11.3.1
Study Area
The methods described in this study are applied to hyperspectral and LiDAR
remote sensing data that have been acquired over the City of Houston, Texas
.29°43
0
16
00
N;95°21
0
24
00
W/. Houston is situated in the American South, close
to the Gulf of Mexico, and comprises an area of roughly 1;500 km
2
(US Census
Bureau
2013
). Due to its location on the Gulf Coastal Plain (Yu et al.
2010
), the city
lies about 13 m above sea level (The City of Houston
2013
) and does not feature
significant topography (Streutker
2002
). With more than two million inhabitants,
Houston constitutes the fourth most populous city in the United States (The City
of Houston
2013
). According to the Köppen-Geiger classification system (Köppen
1936
; Peel et al.
2007
), the city's climate can be described as humid subtropical
(Cfa). In summer, days with air temperatures above 32 °C and a relative humidity
of more than 60 % are not uncommon (National Climatic Data Center,
2012a,b
).
Since, during that season, winds are often light and offer only little relief (University
of Utah
2009
), Houstonians are frequently subjected to considerable heat stress.
Therefore, it is not without reason that Houston has become one of the most air-
conditioned places in the world (Wilson
1992
). Given its specific demographic and
climatic features, the city represents a suitable area of investigation for the present
study.
Search WWH ::
Custom Search