N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 1 Nicolas Ackermann Supervisor:

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


Introduction

Test site & available data

Pre-processing & preliminary investigations

Analysis of the data

Conclusions

Presentation outlinePresentation outline


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


Test site & available dataTest site & available data


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)


Test siteTest site

Topography


Test siteTest site

Forest understory


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


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


Pre-processing & preliminary investigationsPre-processing & preliminary investigations


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.


Local incident angle

Ground scattering area


Correction main components (Castel et al., 2001)



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.



TSX SM 38° HH Asc. 21aug10 Normalised

Gam

ma

noug

ht [d

B]

Aspect [°]

Overcorrection?Crown optical depth?Other effects?

Relief normalisation


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


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


Analysis of the dataAnalysis of the data


Fields of investigationsFields of investigations

Backscatter intensity Multi-temporal Polarisation Frequency Pass

Interferometric coherence Visual interpretations Stem volume


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.



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



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)





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)



Ascending: 6 p.m (afternoon)




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.



Visual interpretations

RapidEye RGB – 13jun09

TSX HS 28may10 - 08jun10

CSK Himage 28sep10 - 29sep10

- 1 day temporal baseline -

- 11 days temporal baseline -



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.



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



Cosmo-SkyMed coherence - Weather information

Weather data for Cosmo-SkyMed acquisitions

Not yet available


Conclusions and outlookConclusions and outlook


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


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


Thuringia Forest – July 2010

Questions ?

Vielen Dank für Ihre Aufmerksamkeit!

Documents

N. Ackermann - Investigations of TSX and CSK backscatter intensity and interferometric coherence over temperate forested areas - 1 Nicolas Ackermann Supervisor: