N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 1
Nicolas Ackermann
Supervisor: Prof. Christiane Schmullius
Co-supervisors: Dr. Christian Thiel, Dr. Maurice Borgeaud
DLR Oberpfaffenhofen, the 16th February 2011
Investigations of TerraSAR-X and Cosmo-SkyMed backscatter intensity and interferometric coherence over temperate forested areas
TSX Science Team Meeting
ENVILAND2 is sponsored by the Space Agency of the German Aerospace Center with federal funds of the German Federal Ministry of Economics and Technology on the basis of legislation by the German Parliamentgrant no. 50 EE 0844 - 50 EE 0847
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 2
Introduction
Test site & available data
Pre-processing & preliminary investigations
Analysis of the data
Conclusions
Presentation outlinePresentation outline
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 3
Context: The monitoring of forested areas represents a great challenge in the context of the
actual Global Warming. The launch of TerraSAR-X spaceborne system in June 2007 has been pioneer of new
capabilities for the retrieval of forest biophysical parameters.
Objectives: Investigate the TSX and CSK backscattter intensity and interferometric coherence. Underline the scattering and decorrelation mechanisms occuring in the temperate forest. Provide some new scientific knowledge for future researches.
IntroductionIntroduction
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 4
Test site & available dataTest site & available data
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 5
Test siteTest site
Thuringia Forest (Germany) Surface: 110 km x 50 km Terrain variations Tree species composition
Scots pinesNorway SpruceEuropean Beech
Climatecool and rainyfrequently clouded
Peculiaritieslogging for forest exploitationKyrill storm (February 2007)
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 6
Test siteTest site
Topography
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 7
Test siteTest site
Forest understory
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 8
SAR data ALOS PALSAR (L-Band, 46 days) TerraSAR-X (X-Band, 11 days) Cosmo-SkyMed (X-Band, 1 day)
Optical data RapidEye Kompsat-2
Ancillary data Laser DEM 5 m Laser points (2004), Orthophotos (2008) HyMap (2008,2009) Forest inventory (1989-2009) Photos with GPS coord. (2009) Weather data Field work
25 km
Available dataAvailable data
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 9
Thuringia Forest test site (state February 2010)
Sensor Radar-
Frequency
Beam Polarisation Incident angle # Scenes
available
TSX X-Band HS HH, VV 21°-45° 41
TSX X-Band SL HH, VV, HH/VV 21°-45° 9
TSX X-Band SM HH/HV, VV/VH 21°-45° 18
CSK X-Band Himage HH 40° 12
Satellite dataSatellite data
80 scenes
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 10
Pre-processing & preliminary investigationsPre-processing & preliminary investigations
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 11
Topographic normalisationTopographic normalisation
Relief
TSX HS 23° HH Asc. 16jul09 Non normalised
LiDAR DEM shaded relief
5 x 10 [km]
High geometrical distorsions by steep incident angle.
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 12
Local incident angle
Ground scattering area
Topographic normalisationTopographic normalisation
Correction main components (Castel et al., 2001)
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 13
Topographic normalisationTopographic normalisation
Experiment - Polarplot
Sensor heading : 350°Sensor azimuth angle : +90°
0°
TSX SM 38° HH Asc. 21aug10 Normalised
TSX SM 38° HH Asc. 21aug10 Non normalised
Gam
ma
noug
ht [d
B]
Aspect [°] Aspect [°]Slope oriented in radar flight direction
High intensity for steep slopes facing radar.
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 14
Topographic normalisationTopographic normalisation
TSX SM 38° HH Asc. 21aug10 Normalised
Gam
ma
noug
ht [d
B]
Aspect [°]
Overcorrection?Crown optical depth?Other effects?
Relief normalisation
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 15
Weather data DWD: Deutsche Wetter Dienst Acquisition period: 2006-2010 Parameters: Precipitation, Snowdepth, Water-equivalent, Wind,
Temperature, Sunshine duration, relative Humidity Pre-processing
Collaboration with FSU geoinformatic institute JAMS (Jena Adaptable Modelling System) Software 2 temporal scales : daily / hourly
Weather data[ .xml ]
Daily outputgeneration
HourlyRegionalised
[ .txt ]
Daily[ raster ]
Hourly Inputconversion
Daily inputconversion
HourlyRegionalisation
DailySelected[ .dat ]
HourlySelected[ .dat ]
DailyRegionalisation
DailyRegionalised
[ .txt ]
Hourly outputgeneration
Hourly[ raster ]
JAMS Software
90m
Station 1
Station 2
Station 5
Station 3
Station 4
Weather dataWeather data
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 16
Weather parameters outputs Raster data
90m spatial resolution
Excel table Describe mean
weather values of the overlapping selected forest stands and satellite data
Temperature [°C]Precipitations [mm]
High: 36
0
Table weather data (simplified version)
Sensor Acquisition-date Daily (4 days meteorological conditions) Hourly (4 hours meteorological conditions)
Beam T°air_mean [°C]
T°air_min [°C]
T°air_max [°C]
Precipitation [mm]
Humidity [%]
Sunshine [hrs]
Wind speed [m/s) T°air_mean
[°C]Precipitation
[mm]Humidity
[%]Wind speed
[m/s}TSX 06/08/2009 17:09:13 spot_074 5.7 3.1 9.1 20.3 81.7 2.1 3.9 2.9 2.8 93.9 4.7TSX 31/10/2009 05:25:57 spot_069 7.6 4.6 11.5 16.7 76.4 2.1 4.0 5.1 2.0 88.4 4.4… … … … … … … … … … … … … …
TSX 31/08/2009 05:34:23 stripNear_009 10.9 4.5 16.7 0.1 69.8 9.6 3.3 11.4 0.0 75.3 3.8
Weather dataWeather data
Daily: 4 days Hourly: 4 hours
Example Daily: 31mar08 - 03apr08
High: 10
0
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 17
Analysis of the dataAnalysis of the data
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 18
Fields of investigationsFields of investigations
Backscatter intensity Multi-temporal Polarisation Frequency Pass
Interferometric coherence Visual interpretations Stem volume
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 19
Pre
cip
[mm
]T
emp
[°]
Win
d [m
/s]
Backscatter intensityBackscatter intensity
TerraSAR-X multi-temporal datasets
Series of TSX HS, 34.4, HH, Asc.
Acquisition dates
Gam
ma
noug
ht [d
B]
Dai
ly
Good species separability over the acquisition time.Precipitations increase the backscatter.
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 20
Backscatter intensityBackscatter intensity
Gam
ma
noug
ht [d
B] –
TS
X S
M H
V.
Gamma nought [dB] – TSX SM HH Gam
ma
noug
ht [d
B] –
TS
X S
M V
V
Gamma nought [dB] – TSX SM HH
- 05may10 - - 22mar09 -
Precip 2.3 [mm] Precip 1.3 [mm]
HV do not allow tree species discrimination.
TerraSAR-X polarisation
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 21
Backscatter intensityBackscatter intensity
TerraSAR-X Frequency
Gam
ma
noug
ht [d
B] –
FB
D 3
4° H
H A
sc.
Gamma nought [dB] – TSX SM 33° HH Asc.- 16jun10 -
- 27
jun1
0 -
A ratio X-band / L-band improves the separation between Norway Spruce and European Beech.
TSX (X-band)
Precip daily: 0.8 [mm]
Precip hourly: 0.0 [mm]
PALSAR (L-band)
Precip daily: 1.1 [mm]
Precip hourly: 0.0 [mm]
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 22
Backscatter intensityBackscatter intensity
TerraSAR-X pass direction
Gam
ma
noug
ht [d
B] –
TS
X H
S H
H 4
6°
Des
c.
Gamma nought [dB] – TSX HS HH 48° Asc. (mon - 28aug09 -
- 26
aug0
9 -
Dew effect is not clearly observable.Intensities differ due to the varying penetration in Ascending and Descending.
Descending: 6 a.m (morning)
Precip daily: 1.1 [mm]
Precip hourly: 0.0 [mm]
Ascending: 6 p.m (afternoon)
Precip daily: 1.7 [mm]
Precip hourly: 0.0 [mm]
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 23
Coherence The degree of coherence can be related to several factors, each expressing a
specific source of decorrelation.
Interferometric coherenceInterferometric coherence
The temporal decorrelation is related to the stability of the objects between the two acquisitions.
The volume decorrelation is related to objects presenting a vertical extension. This factor is spatial baseline dependent.
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 24
Interferometric coherenceInterferometric coherence
Visual interpretations
RapidEye RGB – 13jun09
TSX HS 28may10 - 08jun10
CSK Himage 28sep10 - 29sep10
- 1 day temporal baseline -
- 11 days temporal baseline -
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 25
Interferometric coherenceInterferometric coherence
TerraSAR-X coherence vs Stem volume
Coh
eren
ce –
TS
X H
S H
H 3
7° A
sc.
Stem volume [m3/ha]
- 06
oct
09 –
17o
ct09
-
r2S=0.01
r2B=0.01
As expected, no correlation between stem volume and TSX coherence.
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 26
Interferometric coherenceInterferometric coherence
Cosmo-SkyMed coherence versus Stem volume
r2S= 0.15
r2B=0.02
r2P=0.06
r2S=0.00
r2B=0.01
r2P=0.01
r2S=0.01
r2B=0.01
r2P=0.01
r2S=0.03
r2B=0.01
r2P=0.00
r2S=0.05
r2B=0.00
r2P=0.01
r2B=0.01
r2S=0.11 Perpendicular
baseline
Inte
rfer
omet
ric c
oher
ence
Stem volume [m3/ha]
r2P=0.01
Increase of correlation with higher perpendicular baseline.
1 day temporal baseline
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 27
Interferometric coherenceInterferometric coherence
Cosmo-SkyMed coherence - Weather information
Weather data for Cosmo-SkyMed acquisitions
Not yet available
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Conclusions and outlookConclusions and outlook
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 29
Conclusions and outlookConclusions and outlook
Different investigations of the TSX and CSK backscattter intensity and interferometric coherence have been conducted.
Conclusions and open issues The topography influence is not fully understood. The signal for Norway Spruce and European beech can be separated
with TSX HH or VV. Weather conditions and particularly precipitations affect the backscatter
intensity and interferometric coherence. Interferometric coherence in X-band with 1 day temporal baseline may
show a potential for estimating biomass. Future work
Further investigations for the topographic normalisation Analysis of ALOS PALSAR intensity and interferometric coherence Derivation of indices and ratios between X-band and L-band
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 30
I would like to thank DLR, ESA, ASI and RESA for the distribution of the data
ENVILAND2 is sponsored by the Space Agency of the German Aerospace Center with federal funds of the German Federal Ministry of Economics and Technology on the basis of legislation by the German Parliamentgrant no. 50 EE 0844 - 50 EE 0847
AcknowledgementsAcknowledgements
N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 31
Thuringia Forest – July 2010
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