In: Wagner W., Székely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B
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electoral or district division. At the moment there is no
automatic conversion of addresses or ITN features into land
uses or integration of derived information from remote sensing
sources. There is a need for content specification of the data in
terms of land cover and land use that is currently not in place.
In order to have a clear internal structure of land cover and land
use information there was therefore a need to develop an
ontology that could establish links and associations. This
ontology was developed in the Protégé environment. In the
ontology a high level set of classes were created for both land
cover and land use and relationships established with each
other. It was important to clearly define the different nature of
land use and land cover classes as they are normally mixed up
in many of the existing classifications. For example, the NLUD
land cover classification included classes such as agricultural
land or features such as roads and pavements and the land use
includes water and open land. Also CORINE land cover
classification includes industrial, commercial and transport
units as well as mine, dump and construction sites. So a clear
definition of terms and relations is obviously needed.
The integration of this ontology within the framework follows
the suggestion of Fonseca et al (2000). They suggested an
inheritance structure by which we define general classes that
contain the structure of a generic type of object and then
specialise these classes into subclasses. The subclasses would
inherit all the properties of the super-class and add some more
of its own. In this way the combined use of objects and
ontologies could provide a rich model to represent geographic
entities. It also allows us to provide a sensible relationship
between land cover and land use in order to help define
topographic objects. For example by knowing that the land
cover for a “field” is “trees” and also knowing that the land use
is “fruit production” then we can deduce that a more specific
classification for the area of land is “orchard”. Similarly if we
know that an object is classified as an orchard that it must have
land cover of trees and its land use is “fruit production”. Also
different users have different views on classes. With this
framework they could use the main class as a common starting
point and add their own subclasses that would inherit all the
main properties of that class and server their particular purpose.
Figure 1 reflects this principle.
The link between the object oriented structure of Ordnance
Survey data and a user classification is done through the
intermediate ontology that can translate or incorporate new
attributes or subclasses that then can be added to the existing
features. Ultimately this framework would allow having
automatic customised legends for bespoke maps.
3. BOURNEMOUTH CASE STUDY
3.1 Data and methods
A preliminary trial was focused on the centre of the urban area
of Bournemouth (south of England). The framework was used
as guidance as there was still not an automatic transformation
devised for the trial. The data used for both land cover and land
use comprised:
• MasterMap Topography layer
• MasterMap Address Layer 2
• Mastermap Integrated Transport Network (ITN) layer
• Aerial imagery acquired in June 2006, 4 band spectral
resolution and spatial resolution of 60 cm.
The customised user classification included in this trial was the
NLUD classification.
3.1.1 Land Cover: For the Land Cover classification we
used a combination of the layers described above. The ITN
layer was used to identify artificial non-build up surfaces
whereas the Topography layer did so for artificial build-up
areas. For the classification of natural surfaces there was some
information available on the Topography layer but the
attribution was not rich enough to create a complete
classification. So it was a classification from aerial photography
that provided the most useful information. The classification
consisted of a combination of texture, NDVI and height data
that helped to identify high vegetation (trees) from low
vegetation (shrubs and grass) and bare surfaces using a
Maximum Likelihood classifier in Erdas Imagine.
Object-Oriented Ontology Framework
Figure 1: Object-Oriented Ontology Framework
3.1.2 Land Use: For the Land Use classification Address
layer 2 provided basic information about uses in different
addresses. ITN layer provided information about transport uses.
Topography layer and aerial photography were used to assess
whether there were any morphological or visual signs that could
help distinguish different areas within the urban space
(residential, services, industrial, green open space, etc)
3.2 Results
The Bournemouth trial highlighted different issues for Land
Cover and Land Use.
A Land Cover classification that uses the general classes
defined in the ontology could be quite straight forward using
the data sources available. However this information could be
insufficient depending on the level of granularity of other
classifications. Also it has to be taken into account that the land
cover classification of an urban environment is less complicated
than that of a rural environment. The link between the ontology
general classes and the NLUD classes worked well. However,