Tree Height Estimation Methodology With X - band and P ...earth.esa.int/dragon-2015-programme/lu-tree_height_estimation... · Tree Height Estimation Methodology With X - band and

Tree Height Estimation Methodology With X-band and P-band InSAR Data

Lijun Lu Guoman Huang Qiwei Li CASM

Outline

CASMSAR dataset and test area

Height Estimation with RVoG method Height Estimation with dual-band InSAR method

Results validation and analysis

Conclusions

CASMSAR System

CASMSAR • Cessna Citation aircraft • X-band dual-antenna SAR • P-band repeat pass SAR

Airborne PolInSAR System Band X-band P-band Interferometry Dual-antenna single pass single-antenna repeat-pass Baseline Length 2.2m -- Mode Biastics Mode、Ping-Pong Mode Monostatic Polarization HH、HV、VH、VV HH、HV、VH、VV Resolution（m） 0.3-2.5 1-5 Incident Angle（°） 30-60 30-60 Bandwidth（MHz） 800 200 Flight Altitude 3000-12000m Velocity 450km/h Endurance 3.5hours

Airborne Platform CASM-SAR System Parameters

Test area

• Sichuan Danling • Forest （Eucalyptus，Broadleaf）

CASMSAR dataset

X-band Pauli synthesized image

P-band Pauli synthesized image

Danling forest area

Samples distribution (Google Earth)

Tree Height Measurement

Plot Species Tree Number Mean(m) Std.(m) 1 Eucalyptus 13 11.84 ±1.7 2 Eucalyptus 12 11.53 ±2.1 3 Eucalyptus 12 15.28 ±4.4 4 Eucalyptus 22 11.36 ±1.7 5 Eucalyptus 18 11.28 ±1.3 6 Eucalyptus 18 8.04 ±1.5 7 Eucalyptus 18 16.64 ±5.4 8 Eucalyptus 16 7.41 ±0.7 9 Eucalyptus 17 15.85 ±3.0 10 Eucalyptus 22 15.35 ±3.6 11 Eucalyptus 19 11.74 ±2.6 12 Eucalyptus 14 14.70 ±3.4 13 Eucalyptus 15 9.90 ±0.9 14 Eucalyptus 14 12.20 ±1.0 15 Arborvitae 32 12.00 ±2.0 16 Eucalyptus 16 10.20 ±0.7 17 Eucalyptus 16 14.40 ±3.0 18 Eucalyptus 21 12.50 ±1.0 19 Eucalyptus 16 12.60 ±1.6 20 Eucalyptus 20 15.90 ±1.5 21 Eucalyptus 28 12.20 ±1.3 22 Eucalyptus 16 10.30 ±0.9 23 Eucalyptus 25 8.90 ±1.1 24 Eucalyptus 18 18.10 ±5.2 25 Eucalyptus 18 21.70 ±4.4

Measured Data in Danling

P band data preprocessing steps Track Compensation

Registration

Interferometry

Height Estimation with RVoG method

0( )( )

1 ( )mnzi z C

mnww e

wβ γ µγ

µ+

=+

Tree Height 、Wave Extinction

( )1 22cos

02cos

0

vw w

z

v

h zi z

C h z

e e dz

e dz

σβ θ

σθ

γ =∫

∫vh σ

Volume Coherence 、Ground-to-volume Ratio Topographic Phase Wavenumber 0z

( )µ ωCγ

4sinzB

rπβ

λ θ⊥=

zβ


1、Least squares line fit

Complex coherence can be rewritten using multiple polarization channels as the equation of a straight line in the complex plane. The points of multiple polarization channels can be fit a line.

( )1 20 1 2

1 21 2

( )( , )1 ( )

w wzi z C w ww w e

w wβ γ µ

γµ+

=+


2、Vegetation bias removal

Decide the point on unit cycle as underlying ground topographic phase and remove the phase related to the underlying ground topography.


3、Height and extinction estimation

2

1

1

2

( 1)( 1)

v

v

p h

C p hp ep e

γ −=

−

12

cosp σ

θ= 1 2( )

22

cosw w

zp iσ βθ

= +

Parameter Range Step Tree Height 0≤hv≤30m 1m

Wave Extinction 0≤σ≤0.4db/m 0.01db/m


SVD1 SVD2 SVD3

NR1 NR2 NR3

HH HV VV

P-band Interferometric phase generated from 9 scattering mechanisms

Singular Value Decomposition

Numerical Radius

Polarization channel



• Height estimation result with RVoG method

Dual-band interferometry calculate the X-band and P-band DEM height difference X band radar reflects on the top of the vegetation cover

produces a Digital Surface Model (DSM) P band signal penetrates towards the forest canopy generates a ground level Digital Elevation Model(DEM)

Height Estimation with dual-band InSAR method

Flowchart


X-band SLC

P-band SLC

Registration Elevation

Correction Difference

Tree Height

InSAR Processing

SVD1 SVD2 SVD3

NR1 NR2 NR3

HH HV VV

X-band Interferometric phase generated from 9 scattering mechanisms

Singular Value Decomposition

Numerical Radius

Polarization channel


Tie-points on X-band SAR image Tie-points on P-band SAR image

X-band and P-band SAR imagery coregistration


X-band coregistered SAR image P-band coregistered SAR image

X-band and P-band SAR imagery coregistration

RMSE(root meam square error): 1.9 pixel


Canopy height derived from X-band SAR Ground height derived from P-band SAR

Height difference correction


Num X-band height (m)

P-band height (m)

Difference (m)

001 492.293 532.0429 39.74994 002 455.651 498.6945 43.04353

002A 458.148 499.3564 41.20838 002B 457.431 501.079 43.64795 003 476.21 514.8971 38.68712 004 462.085 506.8705 44.78549

004A 463.534 507.6638 44.12977 004B 460.697 506.4029 45.70593 005 437.291 481.4514 44.16044

Height difference correction

Ground points with high coherence are selected to correct height difference of two elevation results by using a polynomial model


Canopy height derived from X-band SAR Ground height derived from P-band SAR

The elevation results



Height estimation result with dual-band InSAR method


Plot Mean (m) Std (m) RVoG(m) Error (m)

5 11.28 ±1.3 13.16 1.88 6 8.04 ±1.5 12.50 4.46 7 16.64 ±5.4 12.61 4.03 8 7.41 ±0.7 13.95 6.54 9 15.85 ±3.0 11.42 4.43 10 15.35 ±3.6 12.05 3.30 11 11.74 ±2.6 12.05 0.31 12 14.70 ±3.4 14.79 0.09 13 9.90 ±0.9 11.41 1.51 14 12.20 ±1.0 12.93 0.73 15 12.00 ±2.0 12.94 0.94 16 10.20 ±0.7 11.46 1.26 17 14.40 ±3.0 13.64 0.76 18 12.50 ±1.0 11.25 1.25 19 12.60 ±1.6 12.41 0.19 20 15.90 ±1.5 13.08 2.82 21 12.20 ±1.3 12.11 0.09 22 10.30 ±0.9 12.24 1.94 23 8.90 ±1.1 12.59 3.69 24 18.10 ±5.2 16.58 1.52 25 21.70 ±4.4 16.94 4.76

Error mean：2.21m RMSE=2.85m

RVoG height estimation validation


14 samples are in the range of measured tree height, more than half of samples are not in the range of measured tree height that are overestimated .


Plot Mean(m) Std(m) P-band RVoG (m) X-P band InSAR (m) Error (m) 5 11.28 ±1.3 13.16 exception null 6 8.04 ±1.5 12.50 9.63 1.59 7 16.64 ±5.4 12.61 14.23 2.41 8 7.41 ±0.7 13.95 8.01 0.60 9 15.85 ±3.0 11.42 10.93 4.92

10 15.35 ±3.6 12.05 9.02 6.33 11 11.74 ±2.6 12.05 11.10 0.64 12 14.70 ±3.4 14.79 16.53 1.83 13 9.90 ±0.9 11.41 14.23 4.33 14 12.20 ±1.0 12.93 12.87 0.67 15 12.00 ±2.0 12.94 11.74 0.26 16 10.20 ±0.7 11.46 12.55 2.35 17 14.40 ±3.0 13.64 16.40 2.00 18 12.50 ±1.0 11.25 10.84 1.66 19 12.60 ±1.6 12.41 11.31 1.29 20 15.90 ±1.5 13.08 17.02 1.12 21 12.20 ±1.3 12.11 11.44 0.76 22 10.30 ±0.9 12.24 12.39 2.09 23 8.90 ±1.1 12.59 9.76 0.86 24 18.10 ±5.2 16.58 20.19 2.09 25 21.70 ±4.4 16.94 21.05 0.65

Error mean：1.92m RMSE=2.47m

Dual-band InSAR validation

15 samples are in the range of measured tree height, 5 samples are not in the range of measured tree height which of one part are

overestimated and other part are underestimated


P-band RVoG X-P band InSAR

Robustness Low (dependent on model, algorithm)

High

Precision Mean：2.21m RMSE：2.85m

Mean：1.92m RMSE：2.47m

Reliability 50% 75%

Efficiency Low High


Comparison for two methods

Conclusion

Forest tree height can be estmated by RVoG model Dual-band InSAR

Dual-band InSAR method has more advantages than RVoG method

Robustness Precision Reliability Efficiency

Documents

Tree Height Estimation Methodology With X - band and P ...earth.esa.int/dragon-2015-programme/lu-tree_height_estimation... · Tree Height Estimation Methodology With X - band and