Use of airborne hyperspectral data and height information to support urban micro climate characterisation [Elektronische Ressource] / vorgelegt von Wieke Heldens

Wieke Heldens

Informations

• Publié par: julius-maximilians-universitat_wurzburg
• Publié le: 01 janvier 2010
• Nombre de lectures: 13
• Langue: English
• Poids de l'ouvrage: 6 Mo

Extrait

Use of airborne hyperspectral data and
height information to support urban
micro climate characterisation
Dissertation zur Erlangung des
naturwissenschaftlichen Doktorgrades
¨ ¨der Bayerischen Julius-Maximilians-Universitat Wurzburg
Vorgelegt von
Wieke HeldensEingereicht am: 11. Marz¨ 2010
1. Gutachter: Prof. Dr. Stefan Dech
2. Prof. Dr. Hermann Kaufmann
1. Prufer:¨ Prof. Dr. Stefan Dech
¨ ¨2. Prufer: Prof. Dr. Jurgen Rauh
Tag der Disputation: 9. Juni 2010Abstract
The urban micro climate has been increasingly recognised as an important aspect for urban
planning. Therefore, urban planners need reliable information on the micro climatic character-
istics of the urban environment. A suitable spatial scale and large spatial coverage are important
requirements for such information.
This thesis presents a conceptual framework for the use of airborne hyperspectral data to
support urban micro climate characterisation, taking into account the information needs of urban
planning. The potential of hyperspectral remote sensing in characterising the micro climate is
demonstrated and evaluated by applying HyMap airborne hyperspectral and height data to a
case study of the German city of Munich.
The developed conceptual framework consists of three parts. The first is concerned with the
capabilities of airborne hyperspectral remote sensing to map physical urban characteristics. The
high spatial resolution of the sensor allows to separate the relatively small urban objects. The
high spectral resolution enables the identification of the large range of surface materials that
are used in an urban area at up to sub-pixel level. The surface materials are representative for
the urban objects of which the urban landscape is composed. These spatial urban characteristics
strongly influence the urban micro climate.
The second part of the conceptual framework provides an approach to use the hyperspectral
surface information for the characterisation of the urban micro climate. This can be achieved by
integrating the remote sensing material map into a micro climate model. Also spatial indicators
were found to provide useful information on the micro for urban planners. They are
commonly used in urban planning to describe building blocks and are related to several micro
climatic parameters such as temperature and humidity.
The third part of the conceptual framework addresses the combination and presentation of
the derived indicators and simulation results under consideration of the planning requirements.
Building blocks and urban structural types were found to be an adequate means to group and
present the derived information for micro climate related questions to urban planners.
The conceptual framework was successfully applied to a case study in Munich. Airborne
hyperspectral HyMap data has been used to derive a material map at sub-pixel level by multiple
endmember linear spectral unmixing. This technique was developed by the German Research
Centre for Geosciences (GFZ) for applications in Dresden and Potsdam. A priori information on
building locations was used to support the separation between spectrally similar materials used
both on building roofs and non-built surfaces. In addition, surface albedo and leaf area index
are derived from the HyMap data. The sub-pixel material map supported by object height data
is then used to derive spatial indicators, such as imperviousness or building density. To provide
a more detailed micro climate characterisation at building block level, the surface materials,
albedo, leaf area index (LAI) and object height are used as input for simulations with the micro
climate model ENVI-met.
iAbstract
The identification of 31 surface materials represented the urban objects and their structure
in Munich very well. The unmixing approach could be transferred successfully to the Munich
region and a large number of flight lines because of the high level of automatisation of the
algorithm. The material abundances could be identified with a mean absolute error of 2.2 % per
building block and 16 % per cluster of 3x3 pixels (average of all classes). The use and quality
of a priori knowledge on building locations was found to be one of the most important factors
influencing the accuracy.
The surface albedo and leaf area index could also be derived with sufficient accuracy to be
used as input for the ENVI-met model. The albedo is strongly influenced by illumination effects
resulting from sensor viewing angle and object orientation. The estimation of the leaf area index
has to be carried out with care in urban areas, amongst others because of the high number of
mixed pixels.
The spatial indicators building density, vegetation density, imperviousness, building volume,
vegetation volume and dominant roof material were calculated with an absolute mean error of
less than 5 %. This is an improvement in comparison to the accuracy of the spatial indicators
currently used by the municipality of Munich of around 5 %. For the various urban structural
types, typical ranges of the spatial indicators could be identified.
The ENVI-met model was used to simulate the micro climate for 95 building blocks in 16
2areas of 400 x 400 m . Based on the sub-pixel material map, height data, albedo and leaf area
index values, the input data for the simulation of the micro climate in these areas could be gen-
erated without interactive steps, saving tedious manual editing. The sub-pixel information of
the material map helped to solve small co-registration errors between hyperspectral and height
data during the generation of the input data for the model. Areas of interest could thus be repre-
sented realistically in the micro climate simulation environment. A general limitation of remote
sensing data for this application is that tree crows obscure streets and buildings, especially in
detached and semi-detached housing areas.
Two approaches were demonstrated to analyse the micro climate simulation results in com-
bination with the spatial indicators, allowing the characterisation of the micro climate for urban
structural types.
Concluding, this thesis demonstrated the potential of hyperspectral remote sensing to support
urban micro climate characterisation. A detailed mapping of surface materials at sub-pixel level
could be performed. This provides valuable, detailed information on a large range of spatial
characteristics relevant to the assessment of the urban micro climate.
The developed conceptual framework has been proven to be applicable to the case study,
providing a means to characterise the urban micro climate. The remote sensing products and
subsequent micro climatic information are presented at a suitable spatial scale and in under-
standable maps and graphics. The use of well-known spatial indicators and the framework of
urban structural types can simplify the communication with urban planners on the findings on
the micro climate.
Further research is needed primarily on the sensitivity of the micro climate model towards the
remote sensing based input parameters and on the general relation between climate parameters
and spatial indicators by comparison with other cities.
iiZusammenfassung
Fur¨ die Stadtplanung werden klimatische Aspekte zunehmend wichtiger, weil die Klimaver-
anderung¨ besonders in Stadten¨ die Lebensqualitat¨ beeinflussen kann. Hierfur¨ benotigen¨ Stadt-
planer detaillierte Basis-Informationen uber¨ die mikroklimatischen Eigenschaften des urbanen
Gebietes. Dabei sind ein ausreichend detaillierter Maßstab sowie eine großflachige¨ Abdeckung
wichtige Voraussetzungen.
Das Ziel dieser Dissertation ist die Entwicklung und Anwendung von einem konzeptionellen
Rahmenwerk, wie raumlich¨ und spektral hochst¨ aufgeloste¨ Fernerkundungsdaten zur stadtkli-
matischen Charakterisierung verwendet werden konnen.¨ Hierbei sollten die Anforderungen der
Stadtplaner berucksichtigt¨ werden. Zusatzliches¨ Ziel ist das Potenzial dieser sog. hyperspek-
tralen Fernerkundung zur Charakterisierung des Mikroklimas zu demonstrieren. Dazu wird das
konzeptionelle Rahmenwerk an Hand des Fallbeispiels der Stadt Munchen¨ unter Verwendung
von HyMap-Daten angewendet und evaluiert.
Das entwickelte Rahmenwerk besteht aus drei Teilen: Der erste Teil beschreibt, wie rele-
vante Parameter aus Daten eines flugzeuggetragenen Hyperspektralsensors abgeleitet werden
¨ ¨ ¨ ¨ ¨konnen. Die hohe raumliche and spektrale Auflosung dieser Daten ermoglicht es, fur die he-
terogene urbane Landschaft Oberflachenmaterialien¨ auf Subpixel-niveau zu kartieren. Diese
Oberflachenmaterialien¨ sind wiederum reprasentati¨ v fur¨ urbane Objekte, aus welchen die ur-
bane Landschaft zusammengesetzt ist. Das Mikroklima wird stark durch diese raumlichen¨ Merk-
male der Stadt beeinflusst.
Der zweite Teil des Konzepts beschreibt einen Ansatz, wie hyperspektrale Datenprodukte fur¨
die Charakterisierung des Mikroklimas angewendet werden konnen.¨ Dies wird primar¨ durch die
Integration von thematischen Produkten (insbesondere die erwahnte¨ Oberflachenmaterialkarte)¨
in ein Mirkoklima-Simulationsmodell erreicht. Zusatzlich¨ haben sich raumliche¨ Indikatoren als
hilfreich erwiesen, um Stadtplanern Informationen zu mikroklimatischen Eigenschaften b