Rocca.ppt

Page 1Vancouver, IGARSS, July 28, 2011

F RoccaDipartimento di Elettronica e Informazione

Politecnico di Milano

SAR interferometry for sub millimeter land motion studies


ERS -1 - 1991 35 days revisit cycle


Terrain Deformation Monitoring:

The ERS – Envisat era


Decennial Etna motion: vertical


Decennial Etna motion: E-W


Piton de la Fournaise(Isle de la Reunion)

Mad

agas

car

LA REUNION

Piton de la Fournaise


Differential Interferograms: examples (1)S2 Ascending T84

π

-π15

-74

radia

ns

Master: 20031130; Slave: 20030921 Bt=70 [days] Bn=29 [m]

wrapped

unwrapped

wrapped

unwrapped

wrapped

unwrapped


S2 Ascending T84 Velocity Field


S4 Ascending T127 Velocity Field


S2 Ascending T84 Time Series: examples (1)

1

2 3

1

2

3

master

mastermaster


S4 Ascending T127 Time Series: examples (1)

1

2 3

1

2

3

master

mastermaster


Vulcano, Eolie Islands (Italy)

Descending track 49430 scenes Envisat S2

Ascending track 12937 scenes Envisat S2


Velocity field, along LOS


Velocity field, along LOS


Decomposition in East and Vertical velocities

Vertical velocity fieldEasting velocity field

eastwestupdown

Ascending and descending results both cover the crater area and other parts of the island: wherever the two data are simultaneously available, adecomposition from ascending and descending displacement to easting and vertical components is possible, on a grid of 100x100 meters resolution


Displacement Time Series, examples


Displacement Time Series, examples


Landslides detection and monitoringId

en

tify

ing

lan

dslid

es:

Pie

dm

on

t Piedmont landslides






Sentinel 1 A/B 22 years later

12 days revisit cycle


SAR interferometry 20 years later(1991 – 2011)

How about ground motion recovery?

• Target selection for coherence optimization• Absolute geometries• Shorter revisit times with constellations

Nowadays:The path delay measurement is reliable tothe mm, for a reasonable spatial resolution


Densifying the set of reference targets

(Persistent Scatterers)


Covariance matrices of multipass SAR

Rows and columns correspond to progressive times

Examples for:Persistent Scatterers (that terminate)Progressive decorrelationSeasonal effects



SqueeSAR uses nearly all interferograms, weighted with their coherence (see above). Phase linking is

then carried out, estimating the sequence of the N-1 phases using the N(N-1)/2 interferograms.

seasonalMarkov



PS


Squeezing all the information:Squeesar


An example: the InSalah Case (Algeria)

The InSalah Gas storage project is the first CO2 sequestration effort in an active reservoir.

1 million CO2 tons are reinjected into the subsurface each year.

PSInSAR estimated volume and pressure changes, and finally the permeability within the reservoir.



Elastic Model Definition

Apertures (dislocations) and volumetric variations along a fault plane

Inversion using the Poisson ratio in the overburden

Inverted parameters:Fault plane position Center of fault Reject


Inversion results

UD component

Measures Model


Inversion results

EW component

Measures Model



Arrival time and Trajectories

Pressure changes → propagating fronts We use the time derivative of the pressureFrom the time arrivals → permeability

A. Rucci, D. W. Vasco, Fluid pressure arrival time tomography, SEG 2009, Houston

Arrival time Trajectories


The reject across the fault


Cosmo Skymed data:Total change: 1.8mm

28kt/mm


We can map surface deformations into permeability changes; the InSalah story

is condensed in 1 cm surface motion

1 mm sensitivity is achieved today with reduced resolution, but can improve with numerical atmospheric models.

The revisit time is paramount


Effects of motion direction

• The UD component is practically LOS• The SNR of the EW component is just a few dB

down • The NS component can only be retrieved with

speckle correlation. The dispersion σd, referred to the azimuthal resolution is, for N looks:

NN

39.01

2

3 2


MAI: Multiple Aperture InterferometryHowever, if the wide Doppler range of Sentinel - 1 (±0.70) is fully used say for SPOT instead than TOPS scan, then the equivalent azimut resolution is δeq:

mL eq

eqeq

6.057

4.1

42*2

With say 1500 looks (4500m2), the dispersion of the ground motion estimates along the NS direction could be of the order of 1 cm. Multiple Aperture Interferometry proposes to use wide Doppler ranges to achieve a very high equivalent azimuth resolution, even if not completely filling the entire Doppler band (pass band speckle correlation [1]). [1] De Zan F., 2011, Coherent Shift Estimation for Stacks of SAR Images, GRSL to appear


We still have to solve efficiently the problem of the Atmospheric Phase Screen

that biases the outcomes


APS estimation procedure

Model Parameters

DEM


Mathematical modeling of the APS

CByAxyxzKyxyxAPS turbulence ),(),(),(

Characterized by a variogram

K,A,B,C LMS from the data Z from a DEM

)(1 L

d

eSN 4-parameter model


Typical example of atmospheric data

1cmpath traveladditional way two

12

r

r rad


APS from Ground Based RADAR

10-1

mm

2

APS Variogram (stable targets)

100

10-3

10-2

10-1 102101100 10310-2

10 ms 16.6 min

Urban

Mountain

days

APS Variogram (mountain)

mm

2

104

103

102

101

100

10-1

10-3 10-2 10-1 100 101

GBSAR measures APS fluctuations from ms to months (range = 4 km).

The ta power law (Kolmogorov) has been verified on variograms from t > 1 s

APS has considerably less power during night time

APS in short time APS in long time

σφ=1 rad

2hours ~ 40km

mm

2

mm

2


K values: synoptic view

Ascending Descending


6am


6pm


What we can do today with good control of the

Atmospheric Phase Screen


The CESI experimentEstimated displacement (Radarsat 1 data)

-4

-2

0

2

4

6

8

10

12

14

Tempo

Sp

os

tam

en

to [

mm

]

SPOSTAMENTO ORIZZONTALE EFFETTIVO

SPOSTAMENTO ORIZZONTALE STIMATO

-10

-8

-6

-4

-2

0

2

4

6

8

10

12

Tempo

Sp

os

tam

en

to [

mm

]

SPOSTAMENTO VERTICALE EFFETTIVO

SPOSTAMENTO VERTICALE STIMATO

Vertical displacement (ground truth)Vertical displacement (estimated)

Horizontal displacement (ground truth)Horizontal displacement (estimated)

Rmse = 0.58mm (h!); 0.75mm (v)


A Ground Based SAR at the XX dam

The future: UAV, geosynchronous, both?

IBIS-L


Corner 2

Corner 1

Corner 4

Corner 3


Permanent Scatterers analysis : displacement series

16:48 19:12 21:36 00:00 02:24 04:48 07:12 09:36 12:00 14:24-2

-1.5

-1

-0.5

0

0.5

1

1.5

2Multi-target displacement

Acquisition time [hh:mm]

[mm

]

17-Sep

PSgr-21596


Permanent Scatterers analysis : displacement series

16:48 19:12 21:36 00:00 02:24 04:48 07:12 09:36 12:00 14:24-2

-1.5

-1

-0.5

0

0.5

1

1.5

2Multi-target displacement

Acquisition time [hh:mm]

[mm

]

17-Sep

PSgr-15597


Conclusions for the Ground Based SAR (15 h. observation)

The data show coherence > 0.8

The atmospheric effect is very low for the good meteorological conditions

The rms noise is of the order of 0.1mm


What happens if we are far away from PS? we have to estimate the APS from other

sources:

Numerical Weather Predictions

Meris

GPS


InSAR vs NWP

T351, desce, 10UTC

30 images

10 std IWV maps

T172, asce, 21UTC

41 images

20 std IWV maps

The Rome dataset


InSAR vs NWP

Spectral decorrelation

Long spatial wavelengths have a few hours correlation,

short spatial wavelengths decorrelate in less than 1 hour


InSAR vs NWP

Analysis and separation of the stationary (layered) delay

Layered delay Differential delay


MM5 vs InSAR, Rome MM5 vs InSAR, Rome T172 T172 9pm asce

Prediction of the change with height


InSAR vs NWP

MM5:Positive in retrieving the change with heightVery low correlation of turbulent termsStrong dependence on the starting time

WRF performs better than MM5


Meris vs InSARMeris vs InSAR

Cloud coverage can be a problem

Rome T351, morning passes



T351, Meris vs APS power spectra

Similar frequency content after removing the stationary component



And the accuracy is not enough…

Meris IWV [mm]

InSAR IWV [mm]



In desert areas Meris shows good performances (Li et al)

Meris has higher resolution and spectral content than MM5

But in Rome the correlation with InSAR APS is too low


GPS vs InSARGPS vs InSAR

The Como test-site

480 descending, 10am (28 images) 487 ascending, 9pm (38 images)



Delay,Como experiment,descending track

Different ways for estimating the stationary term, for different stations (color)


Ascending Descending

GPS std

InSAR std

diff std

corr coeff

GPS std

InSAR std

diff std

corr coeff

3.69 3.37 3.43 0.53 3.43 1.72 2.85 0.56

2.34 4.27 4.27 0.28 2.73 5.26 3.52 0.79

3.61 5.00 1.98 0.95 0.63 3.35 3.03 0.59

2.94 3.36 1.06 0.95 5.36 6.07 2.79 0.89

2.18 1.15 1.27 0.89 1.67 1.83 2.05 0.32


Best performances, ~50% success


Closer to any PS, the estimate of the APS improves: in a circle of PS with diameter D (m), the mean square APS reduces q times, q is lower than

1000036.0max

Dq

D

qmax

q


In the case of interferogram chaining, if there is a limited coherence γ from one take to the next, the measured phase

is:

2

2

1Ttarget, 1

2

22

4w

L

Nw

NTvatm

eq

L = number of looks (> 4); N = number of takes in the observation timeσatm= dispersion of the APS;w1, w2 noises with unit varianceSignal and noise grow with the number of takes

Even if γ =0.3, just 6 looks are equivalent to a PS, as the coherence is limited only by APS and not by decorrelation.


MM5 has a strong “random” component and a more stable stratification estimation. WRF performs better, further work is needed.

Meris has shown positive results in flat deserted areas, but not in our case studies.

GPS has a success rate of 50%.

The connection between InSAR and the other methodologies lies in the stationary term estimation.

Permanent Scatterers (or interferogram chaining) are still the best way to accurately estimate the APS.


The competition:Optical and GPS levelling:

Approximate results


A recent survey comparison for an accelerator design in Japan






Photon-counting detector with an accuracy of 20 ps (3.3 mm two way) Max point rate ~ 1000 pts/sec. Low atmospheric effects

Photon counting devices


The future?


Recent, forthcoming, and proposed satellites:

- X band: 4xCSK, 2xTSX, Kompsat, TSX, 2xCSK2

- C band: Rsat2, Sentinel - 1 A/B; 3xRCM

- L band: 2xSAOCOM, Palsar 2, Desdyni, TSL

- The proposal for a geosynchronous SAR (EOPUS)


C band data have shown their effectiveness

X band data are good for urban applications

L band data are useful for forest studies

P band data, only, reach ground (tomography)

Remarks


GEOsynchronous SAR for Atmosphere and Terrain observation

Prof. A. Broquetas – UPC Univesitat Politècnica de Catalunya, Electromagnetic and Photonic Eng. Group

Dr. D. D’Aria - ARESYS

Prof. N. Casagli, G. Righini – Università degli studi di Firenze, Dept. of Earth Sciences

Prof. S. Hobbs – Cranfield University, Cranfield Space Research Centre

Prof. A. Monti Guarnieri, Prof. F. Rocca – Politecnico di Milano, Dept. of Electronic and Inf. Science

Prof.sa R. Ferretti – University of L’Aquila, CETEMPS

Prof. M. Nazzareno Pierdicca – Sapienza University of Roma, Dept. of Electronic Engineering

Prof. G. Wadge – University of Reading, Environmental Systems Science Centre

Prof. Dr. H Rott – University of Innsbruck

Dr. C. Svara, Dr. A. Torre – Thales Alenia Space Italia

Earth Explorer EE8 proposal: COM3/EE8/32 GEOSAT


Geosynchronous satellite

The geosynchronous concept is as old as SAR [K. Tomiyasu, 1978]; however, it has never been realized.

To make it feasible we might use:

The 2.4 kW - TWT developed for CoreH20 Long integration times (up to 12 hours), stable targets, PS Quick looks every 20’ to measure and compensate the APS


The problem: water vapor fluctuations

Water vapor changes defocus the scene, unless controlled and compensated. Examples and statistical analysis made by:

Terrasar-X (PSINSAR), GPS, Ground based radar, MM5


GEOSAR for Atmosphere

Mediterranean Hurricane ECMWF medium-scale maps

Yielding high spatial (200 x 10 m) and temporal (20’) resolution water-vapor maps for:

- Weather forecast

- Correction of tropospheric delays for GPS and SAR


GEOSAT: The Wide Beam

GEOSAT may be a guest payload on Italian Space Agency (ASI) SIGMA missions, placed appox 9o longitude.

Look direction would then be close to SN for Europe.

Backgound mission

wide beam over central Europe (2000 km).

NESZ = -19 dB, 0.5x 0.5km resolution,

20’ revisit.

Fine resolution 10 x 10 m (twice daily revisit).

Applications: WV maps, glaciers, urban.


GEOSAT coverage: the SPOT beamGeoseismic risk in Europe

Number of Lanslides in Europe

A 700 km SPOT beam centered on Naples, would be used for monitoring:

- MEDIterranean hurriCANE and Water vapor (thus extending southward the wide beam),

- Many many landlsides

- Active volcanoes


Any TV antenna becomes a good reflector

80 cm antenna SNR = 21 dB (12 hours); SNR=2 dB (10 mins)

Number of home satellite

antennas

1999

millions

2002

millions

1999-2002

Increase

% total

population

% millions % millions

and Pacific 19.5 17.5 -11 -2.1 1 1

and US 13.7 20.1 47 6.4 4 6

EUROPE 33.8 43.6 26 8.7 4 5

Latin America and the 1.6 2.7 62 1.0 0 1

North Africa and the 8.9 11.9 29 2.6 3 4

0.0 0.0 177 0.0 0.0 0

Sub Saharan 0.4 1.2 83 0.3 0 0

World 77.9 96.8 22 16.8 1 2

47 Millions of users parabolas in Europe (2002)



GEOSAT could provide short time (20 min to hours) monitoring for:

atmospheric and hydrogeological effects volcanoes and glaciers

It would have:

wide-swath and SPOT beams

complementarity to LEO for revisit, look angle

compatibility with Telecom, as a guest payload.


Conclusions For ground motion applications, spatial resolution is not essential, but short

revisit time and good vertical precision are paramount

With a dense and long set of PS (desert areas), we are already much below the millimeter error. In the future, NWP and GPS may help.

The geosynchronous satellite could help to obtain continuous observation.

Optical and GPS systems, at the moment, do not offer either spatial continuity or sufficient precision.

Date post:	20-May-2015
Category:	Technology
Upload:	grssieee
View:	1,485 times
Download:	0 times

Rocca.ppt

Technology