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Mapping Flooded Areas in 
Mapping Flooded Areas in 
Nadi Using TerraSAR
Nadi Using TerraSAR
-
-
X 
X 
Data and ERDAS
Data and ERDAS
Wolf Forstreuter
Wolf Forstreuter
TerraSAR
TerraSAR
-
-
X
X
(Radar Satellite)
(Radar Satellite)
•
•
System records with high resolution 
System records with high resolution 
while area is still under thick cloud 
while area is still under thick cloud 
cover
cover
•
•
Download 12 hours after recording
Download 12 hours after recording
•
•
However, data recording 
However, data recording 
not
not
on high
on high
-
-
peak of flood
peak of flood
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Scene Coverage
Scene Coverage
•
•
Synthetic Aperture 
Synthetic Aperture 
Radar
Radar
•
•
Signal penetrates 
Signal penetrates 
clouds !
clouds !
•
•
3 m resolution
3 m resolution
•
•
Recorded:  
Recorded:  
12.01.09 / 18:30
12.01.09 / 18:30
•
•
Cost: 
Cost: 
€
€
3,750 
3,750 
• Coverage:             
30 x 60 = 1,800 km
2
Radar Reflection
Radar Reflection
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Operating Principle
Operating Principle
Polarisation
Polarisation
H = horizontal
H = horizontal
V = vertical
V = vertical
HH = horizontal send and receive
HH = horizontal send and receive
VV = vertical send and receive
VV = vertical send and receive
HV = horizontal send vertical receive
HV = horizontal send vertical receive
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Reflection of Radar 
Reflection of Radar 
depends on:
depends on:
a)
a)
angle of the object surface to the 
angle of the object surface to the 
radar beam, 
radar beam, 
b)
b)
dielectric constant of the object, 
dielectric constant of the object, 
c)
c)
roughness of the object surface
roughness of the object surface
These influences vary by: 
These influences vary by: 
a)
a)
wavelengths used by the system, 
wavelengths used by the system, 
b)
b)
polarisation of the transmitted 
polarisation of the transmitted 
signal, 
signal, 
c)
c)
direction of the transmitted signal.
direction of the transmitted signal.
Housing Areas
Housing Areas
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Water None
Water None
-
-
Water
Water
Image to Image Rectification 
Image to Image Rectification 
•
•
Pan
Pan
-
-
sharpened QuickBird available 
sharpened QuickBird available 
as reference for image rectification
as reference for image rectification
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Visual Analysis (Mapping) of 
Visual Analysis (Mapping) of 
Infrastructure at 1:10,000
Infrastructure at 1:10,000
•
•
Digitising of road network
Digitising of road network
•
•
Digitising of river system and 
Digitising of river system and 
normal water bodies
normal water bodies
•
•
Digitising of houses
Digitising of houses
•
•
Digitising of flooded areas
Digitising of flooded areas
•
•
4 people 1 
4 people 1 
½
½
days each
days each
Semi Automatic Analysis
Semi Automatic Analysis
• Speckle suppression to reduce 
salt and pepper effect
• Density slicing to separate water 
and non water pixels
• Editing layer density slicing
• Deleting small areas from “water 
non water layer” through filter
• Raster to vector conversion
•
•
Speckle suppression to reduce 
Speckle suppression to reduce 
salt and pepper effect
salt and pepper effect
•
•
Density slicing to separate water 
Density slicing to separate water 
and non water pixels
and non water pixels
•
•
Editing layer density slicing
Editing layer density slicing
•
•
Deleting small areas from 
Deleting small areas from 
“
“
water 
water 
non water layer
non water layer
”
”
through filter
through filter
•
•
Raster to vector conversion
Raster to vector conversion
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Comparison:
Comparison:
Visual and Semi Automatic
Visual and Semi Automatic
Flood Mapping within 2 
Flood Mapping within 2 
Hours?
Hours?
YES 
YES 
…
…
. if :
. if :
1.
1.
Semi automatic analysis is 
Semi automatic analysis is 
applied
applied
2.
2.
Reference data is available for 
Reference data is available for 
image correction
image correction
3.
3.
Infrastructure and river system 
Infrastructure and river system 
is available at 1:10,000 scale
is available at 1:10,000 scale
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Workflow & Information Flow
Workflow & Information Flow
NDMO Nadi
SOPAC CRP
informs (after 2 days)
informs (after 2 days)
informs (after 6 hours)
informs (after 6 hours)
SOPAC GIS&RS
InfoTerra in Germany
informs  directly
informs  directly
InfoTerra Satellite 
Programming Deptm. 
SOPAC Finance
Informs (1 day)
Informs (1 day)
identifies funds (1 day)
identifies funds (1 day)
Satellite records
data download
over Kiruna
from Kiruna to
Infoterra 
data pre-processing 
12 hours
12 hours
data download
from InfoTerra
How to Reduce Response 
How to Reduce Response 
Time ?
Time ?
• NDMOs must know the technique 
available [on the way]
• Funds must be directly addressable [ ✔ ]
• Link to other space borne radar systems 
to reduce programming time [✔]
• 24/7 response of satellite companies [ ✔ ]
•
•
NDMOs
NDMOs
must know the technique 
must know the technique 
available [
available [
on the way
on the way
]
]
•
•
Funds must be directly addressable [ 
Funds must be directly addressable [ 
✔
✔
]
]
•
•
Link to other space borne radar systems 
Link to other space borne radar systems 
to reduce programming time [
to reduce programming time [
✔
✔
]
]
•
•
24
24
/
/
7 response of satellite companies [ 
7 response of satellite companies [ 
✔
✔
]
]
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Other New Satellites
Other New Satellites
• 5 satellites in space
• 50 cm frame 5.5 km
• 1 m frame 8 km x 60 km
• Response 10 hours after 
recording
• Operational since 22 July 2008  
•
•
5 satellites in space
5 satellites in space
•
•
50 cm frame 5.5 km
50 cm frame 5.5 km
•
•
1 m frame 8 km x 60 km
1 m frame 8 km x 60 km
•
•
Response 10 hours after 
Response 10 hours after 
recording
recording
•
•
Operational since 22 July 2008  
Operational since 22 July 2008  
SAR-Lupe
SAR-Lupe
Also in Space:
Also in Space:
RadarSat
RadarSat
2
2
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Reducing the Disaster 
Reducing the Disaster 
Response Time
Response Time
NDMO informs
SOPAC
Flood appears
SOPAC orders
image data
Programming
satellite
Data recording
Data pre-processing &
downloading
Data processing
at SOPAC
Map send to
NDMO
1
1
1
6
10 2
Time
Thanks
Thanks