Estimation of Ground Topography in Forested Terrain by means of Pol...

[email protected] 27-Junuary-2009

Estimation of Ground Topography in Forested Terrain by means of Pol-InSAR Koichi Iribe1, Carlos Lopez-Martinez2, Kostas Papathanassiou1, Irena Hajnsek1

1 Microwaves and Radar Institute German Aerospace Center DLR2 Technical University of Catalonia UPC

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Interferometric Coherence

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Sweden

Finland

Norway

Denmark

0°

10°E

10°E 20°E

20°E

30°E

55°N55°N

60°N60°N

65°N

65°N

70°N

70°N

Remningstorp

Brattåker

Vidsel

Västra Götaland

Västerbotten

BioSAR CampaignTime: 8th of March to 3rd of May 2007.Main objective: Estimation of the forest biomass in order to support carbon modelling using longer wavelength (L- and P-band).Observation system: DLR E-SAR (Airborne).Test site: Remningstorp, Southern Sweden (58˚28΄N, 13˚38΄E).

Topography: Fairly flat with small variations ranging between 108m and 140m above sea level.Tree property:

Predom. Spruce but also pine stands.Homogenous and managed standsBiomass level: up to 300t/haForest heights: up to 25 - 30m

In this presentation, P- and L-band polarimetric and interferometric repeat pass datasets are employed.

Landscape of Test Site.

Remningstorp Test Site in P- & L-band Radar Image and LIDAR ImageBlack area represents minimum height or no data.LIDAR Digital Terrain Model (DTM) is used for the validation.

108m

140m

azim

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LIDAR Digital Terrain Model (Projected onto P-band SLC image)

L-band Pauli decomposed image

Double bounceVolume scattering

Single bounce


Single bounce

P-band Pauli decomposed image

P-band Track ConfigurationQuad-pol 70MHz P-band images acquired in a repeat-pass PolInSAR mode.Dataset acquired in May is employed.6 tracks, 14 interferometric pairs. (exclude 0m baseline pair)

P-band HH Pol. Interferometric Coherence ΓHH

10m Baseline. 30m Baseline. 50m Baseline.0

1

Distribution of Interferometric Coherence ΓHH

10m Baseline.

30m Baseline.

50m Baseline.

Bare Area.Forested Area.

P-band HH Pol. Interferometric Phase φP

10m Baseline. 30m Baseline. 50m Baseline.-π

π

Differential Phase betweenφP and Topographic Phase φLIDAR


π

Differential Phase, φP – φLIDAR

10m Baseline.

30m Baseline.

50m Baseline.


Differential Height, P-band InSAR DEM – LIDAR DTM

10m Baseline.

30m Baseline.

50m Baseline.


0.01< kz <0.08

0.04< kz <0.23

0.08< kz <0.38

Differential Height, φo Height – LIDAR DTM

10m Baseline.

30m Baseline.

50m Baseline.


0.01< kz <0.08

0.04< kz <0.23

0.08< kz <0.38

Estimated Pbandφo Height using Multi-Baseline Data


P-band, 10m (2 pairs), 20m (2 pairs), 30m (3 pairs), 40m (2 pairs), 50m (1 pair), 60m (2 pairs), 70m (2 pairs) baseline data.Baseline length weighting combination, higher for longer length.

Smaller variance for both bare area and forested area.Bias from vegetation is less.Even bare area, which shows low coherence, shows small variance.

108m

140mLIDAR Digital Terrain Model

(DTM)P-band Pauli decomposed

image

Estimated P-bandφoHeight using Multi-Baseline Data

azim

uth

range


Single bounce

Estimated P-band φo Height using 14 baseline data

L-band HH Pol. Interferometric Coherence ΓHH

8m Baseline. 16m Baseline. 24m Baseline.0

1

Distribution of Interferometric Coherence ΓHH

8m Baseline.

16m Baseline.

24m Baseline.


L-band HH Pol. Interferometric Phase φL


π

Differential Phase betweenφL and Topographic Phase φLIDAR


π

Differential Phase, φL – φLIDAR

8m Baseline, HH Pol.

8m Baseline, VV Pol.

8m Baseline, XX Pol.


Differential Height, L-band InSAR DEM – LIDAR DTM

8m Baseline, HH Pol.

8m Baseline, VV Pol.

8m Baseline, XX Pol.


0.01< kz <0.28

0.01< kz <0.28

0.01< kz <0.28


8m Baseline, Single-Baseline.


8m Baseline, 2-Baseline.

0.01< kz <0.28

8m Baseline, 5-Baseline.

108m

140mLIDAR Digital Terrain Model

(DTM)L-band Pauli decomposed

image

Estimated L-bandφoHeight using Multi-Baseline Data

azim

uth

range

Estimated L-band φo Height using multi-baseline data.


Single bounce

Summary and Future Work

P-bandEstimated ground topography φo by means of PolInSAR shows,

Less bias and smaller variance.Improvement by using multi-baseline dataset.

L-bandGround topography φo was estimated using shorter baseline (8m) which show still useful interferometric phase quality.

Less bias but still larger variance.Improvement by using multi-baseline dataset.

Investigation of residual motion error of platform.Quantitative analysis.


8m Baseline, Single-Baseline.


8m Baseline, Multi-Baseline.

Combined with 5 baseline data with 8m length.

Discrimination of Forested Area and Bare Area

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From view point of SNR, forested area and bare area are discriminated.High SNR is associated as forest area, low SNR is as bare area.

0

100

SNR image.

Index of forested area.

Index of bare area.

Utilization of CSs for phi_0 estimation (1/2)

CS candidates with low SLC CSs with high coherence (not interferometric coherence)

Phase error map acquired using CSs [rad]

Histogram of height difference

Before the removal of phase error

Histogram of height difference

After the removal of phase error

Utilization of CSs for phi_0 estimation (2/2)

Estimation of Ground Topography in Forested Terrain by means of Pol...

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