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Sigma 0 for Urban Change Detection
Dr. François Cavayas
Geography
Department, University of Montreal,
Canada,
Tel: +1-514 343 8016,
E-mail: Francois.cavayas@umontreal.ca
Dr. Yves Baudouin
eography
Department, University of Québec in Montreal,
Canada,
Tel: +1-514 987-3000 7706#,
E-mail: Baudouin.yves@uqam.ca
Claire Gosselin
Synetix Inc.,
Canada, Tel: +1-514-598-1991,
E-mail: claire@gosselin.com
Dr. Rejean Simard
Synetix
inc., Malaysia, Tel : +60-12-235-8397,
E-mail: rejean@simard.com
ABSTRACT:Many
public-sector agencies require current, reliable
data on urbanized areas. Updating geospatial
databases at scales ranging from 1:10 000 to
1:250 000 stands out as one of the major
concerns of agencies involved in land
management. What they are looking for is an
efficient and economical system for detecting
urban change and facilitating map updating.
SIGMA 0 , a new geomatics system aimed at
updating land-use maps in urban areas with
RADARSAT-1 or Envisat imagery, could be just
what they need.
Until now, there has
been no automated, rapid, and effective method
for detecting change. Part of the problem lies
with optical satellite images usually applied
for change detection. In fact urban area
heterogeneity and object size make using very
high resolution images (less than 5 m)
necessary. These images, however, contain an
excessive amount of spatial and spectral detail
that makes tasks as basic as determining by
automatic means a building's perimeter
complicated and very often inaccurate.
RADARSAT and Envisat offer a solution
with images that have a resolution between 10
and 25 m that are not affected by weather
conditions. Radar images are sensitive to the
presence of elevated objects, such as buildings.
The appearance of buildings on areas previously
known as vacant is an undeniable indicator of
urban change . Tests carried out with SIGMA 0
show that it automatically detects nearly all
new buildings erected on the vacant lots
indicated on the land-use map to be updated. The
percentage of error is usually inferior to 5%.
SIGMA 0 was developed by the Laboratory
of Remote Sensing, University of Montreal, and
the GIS Laboratory, University of Quebec in
Montreal. It is presently being commercialized
and adapted for new map updating applications
with the collaboration of SYNETIX and under the
financial support of the Canadian Space Agency
and the Quebec Ministry of Economic Development,
and Regional and Research.
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