Analysis of forest parameters and agricultural field structure

1. Analysis of forest parameters and agricultural field structure from high resolution PolInSAR X band data Franck Garestier(1), Kostas Papathanassiou(2), Irena Hajnsek(2), Pascale Dubois-Fernandez(1) & Xavier Dupuis(1) (1) ONERA, BA 701, Ecole de l ’Air, 13661 Salon AIR, France (2) DLR, Microwave and Radar Institute, 8230 Wessling, Germany

2. Plan of the presentation • Presentation of the RITAS data • Ground truth campaigns (during and after acquisition) • Pine forest: • Random Volume over Ground model • Assumptions and correction of the data • Mean extinction coefficient estimation • Wheat type fields: • Signature of oriented volume observation • Conclusion

3. 0 25 50° Representation of Pauli basis polarimetric HH+VVHV HH-VV Alpha angle map Presentation of the data Campaign: Radar Imagerie Thématique Agricole et Sols Team: INRA, CETP, BRGM, CEMAGREF and ONERA Date: acquisition in March 2002 by R.A.M.S.E.S. system • Data: X band mono-pass PolInSAR Size of the resolution cell: 0.9 m x 0.9 m Swath: 800 m Mean incidence angle: 30°

4. vineyard Brussels sproutsapricot hay building peachwheat and clovergreenhouse litmus tree hedges pear bare surfaces almonds apple pine forestgrass Ground truth campaigns INRA test site orchards : specie, height, biomass, maturity, water content soils: roughness, hygrometry during the acquisition The entire data vegetation: specie, height, tree density, maturity buildings: height after the acquisition optic radar I.N.R.A. test site, Avignon, France Montfavet

5. Presentation of the RITAS data • Ground truth campaigns (during and after acquisition) • Pine forest: • Random Volume over Ground model • Assumptions and correction of the data • Mean extinction coefficient estimation • Wheat type fields: • Signature of oriented volume observation • Conclusion

6. Canopy: extinction independent of the polarization mean extinction coefficient volume height Soil: impenetrable scatterer interferometric phase System parameters: vertical wavenumber incidence angle Pine forest: Random Volume over Ground model Cloude & Papathanassiou 2001 18 m Representation of Pauli basis polarimetric HH+VVHV HH-VV Polarimetric DEM HHHV VV

7. (HV or ) Pine forest: interferometric coherence Interferometric coherence for a polarization straight line in the complex plane Ground to volume ratio with and the coherency matrixes of canopy and soil Interferometric coherence of the “volume only” contribution depends on and Im Re Complex plane

8. Transmit | Receive switch Coherence maps master HH-HH HV-HV H and V successively H and V simultaneously slave R.A.M.S.E.S. system configuration VH-VH VV-VV (transmit/ received) Pine forest: limitation of the data antennas High rate switch dysfunction during the flight: problem in V emission decorrelation on the whole images Decorrelation on VH and VV channel (small loss of coherence for VV)

9. Pine forest: dual (lite) pol Im The slight loss of coherence in VV channel should induce a bias in parameter extraction overestimation of the forest height use of only two polarisations:HHandHV degradation of the estimation (compared to Quad-pol mode) interferometric coherence associated toHV HH HV VV Re Complex plane

10. Pine forest: canopy decorrelation Im range axis resolution cell gHV gHH Re Complex plane Interferometric phase of the ground remains unchanged The “roughness” of the canopy induces a scalar decorrelation of decorrelation coefficient only applied on the volume contribution Radial correction (~ +0,07) Impossible to extract and simultaneously Assumption on to estimate forest height

11. 0 20 40 60 0 20 40 60 Interferometric height (m) of soil, HH and HV phase centers Interferometric height (m) of soil, HH, HV andVV phase centers Pine forest: coherences and heights slight underestimation of the forest height 6 m vertical separation (~9°) 0 1 Coherence of HH and HV channels Mono-pass acquisition: high coherences 0.9 < < 0.95 (Coherence observed on bare surfaces: 0.98) Phase standard deviation : - phase estimation accuracy : ~3° - forest structure

12. Pine forest: volume height 18 m height pine forest without underlying topography 2 1,8 1,6 1,4 1,2 1 0,8 0,6 0,4 (dB/m) 0 10 20 30 0 10 20 30 Height (m) histogram of the estimated ground level Forest height (m) histograms for different extinction values Height retrieved with high extinction Dual-pol mode reduces the accuracy of estimation

13. Pine forest: extinction estimation 18 m height pine forest without underlying topography Mean forest height (m) Mean forest height error (m) Mean extinction coefficient (dB/m) Mean extinction coefficient error (dB/m) Mean extinction coefficient of a sparse pine forest at X band A large interval of mean extinction coefficient gives a satisfying inversion. Accuracy of : 0.5 dB/m

14. Presentation of the RITAS data • Ground truth campaigns (during and after acquisition) • Pine forest: • Random Volume over Ground model • Assumptions and correction of the data • Mean extinction coefficient estimation • Wheat type fields: • Signature of oriented volume observation • Conclusion

15. Wheat, hay and high grass Wheat, hay and high grass HHHVVV 0,9 0,8 0,9 1 Coherence Coherence 0,8 1 VV decorrelation induced by vertical structure 20 40 -20 0 20 40 -20 0 oriented volume Sigma0 (dB) Sigma0 (dB) Wheat type fields: orientation effect Bare soil surface HHHVVV INRA: 8 wheat orchards Representation of Pauli basis polarimetric HH+VVHV HH-VV

16. Conclusion Pine forest Phase centers corresponding to HH and HV separated wave penetration in the canopy of a sparse pine forest at X band determination of a high mean extinction coefficient using RVoG model forest height estimation: low sensitivity to mean extinction coefficient (HV phase center close to the top of the canopy) Wheat type fields observation of an orientation effect due to the vertical structure