Forest Height Estimation with X- Band InSAR: Phase Centre Location versus RVoGFlorian Kugler, Irena Hajnsek, Seung-Kuk Lee & Konstantinos PapathanassiouGerman Aerospace Center (DLR)Microwaves and Radar Institute (HR)

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Lineout

Test Sites:

FinSAR CampaignINDREX II: MawasKobernausser WaldTempoSAR Campaign: TraunsteinBiosar II Campaign: Krycklan

Issues:

Phase Centre HeightForest HeightExtinctionComparision/Combination of different baselines

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Height Validation X band vs L band boreal forest Southern Finnland

X band validated against Scatterometer

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• Peat swamp forest

• Forest Height: 15m – 25m

• Biomass around 100-350t/ha

• Uniform structure

• Open canopy

• Flat Topography

INDREX-II: Mawas Test Site

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Mawas X band Validation with Lidar

Lidar Strip was divided into100 equal samples

Phase Center Height

Inversion I using φ0 fromunvegetatedarea

Inversion IIusing σ0.3 d B/m(mean ExtinctionInversion I)

Lidar StripReference Height: Top Canopy height 100(100 tallest tree per hectar)

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Test Site Kobernausser Wald

Kobernausser Wald: • Upper Austria• Temperate managed forest• Hilly Topography• Inhomogenous Composition• Stands of different Heights

from 4 to 35m and different age and differentbiomass

• Domintated by Coniferous trees• Canopy mainly closed

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KobernausserWaldDataset

X Band Polarisation VVSingle PassBaseline :0.8m

Lidar StripInSAR Coherence Amplitude Image

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Kobernausser Wald X band Validation with LidarPhase Center

Lidarh100

InversionHeights

InversionHeights

Phase Center

Reference Height: Top Canopy height h100(100 tallest tree per hectar)

Inversion Iusing φ0 from Lidar

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Kobernausser Wald X band Extinction Estimation

Extinctionfrom heightestimation

Extinctionfrom LidarInversion

2dB/m

1dB/m

0dB/m

Stand:Mean Extinction from

Inversion: 0.79dB/mMean Extinction from

Lidar h100: 0.82dB/mMean Ground to Volume Ratio: 0.05

Mean forest Height, 25.7m

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Traunstein Test Site

Forest type Temperate Topography Moderate slopes

25 ~ 35mN. Spruce, E. Beech, White Fir

40 ~ 450 t/ha

HeightSpeciesBiomass

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Temposar dataFull Baseline Half Baseline

Coherence 0 to 1 Coherence 0 to 1Phase -π to π Phase -π to π

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Estimated Forest Heights Full Baseline

Inversion height Scattering Centre40m

20m

0m

Inversion using external ground phase

Tends to underestimate high forests

Scattering Centre clearly below estimated forest height

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Estimated Forest Heights Half Baseline

40m

20m

0m

Inversion height Scattering Centre

Inversion using external ground phaseTends to underestimate high forests

Scattering Centre clearly below estimated forest height

Good Inversion Performance in near range

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Estimated Extinction Full Baseline Half Baseline

Estimated with Reference Height

Estimated with Reference Height

Estimated from Height Inversion

Estimated from Height Inversion

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Lidar Tree Vegetation height

40m

20m

0m

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Biosar II Test Site Krycklan Sweden

Krycklan forest:Location:• middle Sweden• boreal forest• high topography

Composition• stands of different Height• maximum forest height: ~ 30m• mean forest height: 17m

• stands of different age and different biomass

• domintated by Coniferoustrees

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Biosar data Full Baseline Half Baseline

Coherence 0 to 1 Coherence 0 to 1Phase -π to π Phase -π to π

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Biosar dual Baseline Inversion results

Extinction Forest Height

2dB/m

1dB/m

0dB/m

40m

20m

0m

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Summary Forest Height Inversion using X-Band

Forest height estimation using X band provides prommissing results fortropical as well as for temperate & boreal forest conditiions

X band Phase Center is significantly lower than Pol-InSAR forest height

Especially in less dense forest conditions as can be found in boreal forests X band could provide good results

Limitting factor for X band is forest density

If there is an external DEM available we can go even further

The results show a high potential of TanDEMX for forest height estimation in certain ecosystems, even if Quad or Dual Pol data are available