tandem-x interferometric processing chain and sar · pdf file · 2008-11-26tandem-x...
TRANSCRIPT
TanDEM-X Science MeetingNov. 2008
TanDEM-X Interferometric Processing Chain and SAR Products Thomas Fritz H. Breit, M. Eineder, M. Lachaise & ITP Development Team
Slide 2
From Acquisitions to Products -The TanDEM-X InSAR Processing Chain Basics
Higher level processing of operational acquisition modes onlyoperational DEM generation for a specific subset of acquisition modes Systematic processing of all mission data (~400 DEM scenes / day)Data driven processingstarts when complete joint data take and all auxiliary products are available at processing system
One type of products – co-registered SSCs (CoSSCs) Processing into standardized archive products, retrieve them as delivery products via the catalogueNo processing to different product variants from raw data on user request (unlike TS-X)Monostatic processing of active channel data to MGD,GEC,EEC, …TerraSAR-X mission like products possible for restricted set of acquisitionsRaw data of experimental modes can be processed with help from DLR scientists
Slide 3
TanDEM-X DEMDEM--, , Operational and Experimental Acquisition ModesClassification of acquisitions in “4D mode space”
Imaging Mode of each instrument:SMSM, SL, HS, SC, (DRA-ATI, …)Polarization Mode of each instrument:SingleSingle, Dual, Twin, DRA-Quad
Cooperative Mode of the two Instruments:bistaticbistatic, alternating bistatic, pursuit monostatic, none (TS-X mission)& experimental modesFormation Geometry:smallsmall or large along & across track separation / baseline
IM
coop
geo
pol
DEMs
Exp. Prod.
Exp. Mode
Slide 4
Operational Modes Experimental Modes
TanDEM-X Cooperative Mode (of TSX + TDX sats)
Bistatic Alternating Bistatic
Pursuit Monostatic
Any
Instrument Imaging Modes Stripmap (SM) Stripmap (SM) all basic modes Any
Instrument Polarization Modes all basic modes single pol. all basic modes Any
Formation Geometry
Cross-track baselines < 4 km < 4 km < 4 km Any
Along-track baselines < 1 km < 1 km Any (large ones) Any
Processing and Products
TanDEM-X Screening L0 products
All All All raw data ( + base annotation)
DEM products SM single pol - SM single pol(fallback solution)
-
Experimental products by ITP
CoSSC+ Interferogram
2 (Co)SSCs CoSSC for SM-S best effort (@ DLR)
Experimental products by TerraSAR-X TMSP monostatic processing
TerraSAR-X L1b products* of mono-static channel
- 2 x TerraSAR-X L1b products*for all modes
best effort (@ DLR)
*: The TerraSAR-X basic product spec does not apply in terms of performance
exp.prod.
oper.prod.
TanDEM-X Acquisition Modes and Products
Slide 5
DEMDEM Acquisition & Processing Plan
Year 1: full coverage with smaller baseline
height ambiguity ~ 40 m good for moderate terrain
Year 2: repeat with larger baselineheight ambiguity ~ 30 m gives full accuracyrobust Phase Unwrapping with supporting data from first year
dual baseline PU
Year 3: more baselines & angles tofill shadow and layover regionsand support phase unwrapping of difficult areas
maximum likelihood reconstruction method
-
-
terrain slope / shadow & layover
illumination
DEM
erro
r swath shift – clapboard pattern
Slide 6
Integrated TanDEM-X Processor (ITP)
ITP based on TerraSAR-X / TMSP & SRTM / InSAR-DEM heritage
modular ITP executes the complete “SAR – InSAR – DEM” processing chain, invoked in different scenarios:
1. Basic SAR data parameter screening at the receiving stations2. Fast quality check of joint TanDEM-X acquisitions3. (Bistatic) SAR focussing to co-registered SSCs (CoSSCs)
& InSAR processing & generation of Raw DEMs4. Experimental product generation for operational modes
(+ TMSP generated monostatic products)
feedback loop with triggering from Mosaicking & Calibration Processor (MCP) for optimal uniform DEM product performance (reprocessing)
Slide 7
TanDEM-XScreener
receiving stationTanDEM-XScreener
raw 1 raw 2
SAR
InSAR
PU / DEM
RawDEMs CoSSCs
MCP control
MCP
final DEM(s)
control system
data driven
(In-)SARWorkflow
DEMWorkflow
systematic & operator interaction
GroundStationNetwork
Product Library DLR (PL)
WorkflowOverview
triggering of(re-)processing&customized raw DEM generation
Raw DEM(re-)processing& multi-BL support
PL
-- individualindividualdata take qualitydata take quality
-- joint (for planning)joint (for planning)
Slide 8
TanDEM-X Processing Standard (By-)Products:Co-registered Single-look Slant-range Complex Products (CoSSCs)
ITP
CoSSC
SSC (“TS-X L1b”)sat1
SSC (“TS-X L1b”)sat2
common RawDEM+
DIMS PL: CoSSC Archive
CoSSC deliveryproduct
MCP internal useTanDEM-X acquisitionfor DEM generation
h
SSSLS
Slide 9
ITP Bistatic Focussing
operational bistatic DEM acquisitions are restricted to limited combinations of instrument modes & close formation flight with very small bistatic angles.main complication: sync pulse processing and timing corrections
=> ITP „bistatic“ focussing uses pseudo-monostatic hyperbolic approach for DLR hybrid Chirp Scaling algorithm
primarily interferometric mission => operational SAR processing is serving the InSAR system as „pre-processing“ step
common parameter estimation for focussing & InSARphase preservation / phase synchronization co-registration of (passive) SSC to master common band & spectral shift filtering included in focussing steps
Slide 10
TerraSAR-X / TanDEM-X: Interferometry Meets Stereo Radargrammetry – Terrain Adaptive Coregistration
major InSAR SW update [N. Adam]:coregistration (reference DEM & geometry. Refinement: signal correl.)
Height difference bottom-peak: 1300 m76 fringes1.18 m slant range parallax1.3 pixel misresgistration if not compensated!
= complete loss of coherence
coherencewith “classic”polynomialco-registration
not suitedfor high-res.X-bandinterferometry!!!
Slide 11
Use of Maximum Likelihood Estimator in slant range geometry-> Supported by reference phases from (SRTM-)DEM & Delta-k
-> Interferogram with larger baseline is rescaled to master geometry
Phases are unwrapped using their different PDF (noisy)
Phase gradients are used for spike reduction
Δϕ [cycles/sample]-1/2 0 1/2
Ifgrm 1
with baseline B1
Δϕ [cycles/sample]
Ifgrm 2
with baseline B2
pdf of phase difference
scaling
by ∼B1/B2
multi-baseline estimate
-1/2 0 1/2
PDFs of master and „slave“broad PDF of reference phase
-> joint PDF (magenta)
Pixel 2 (neighbor)
Pixel 1
PDF of master and „slave“gradients („pixel 1“ – „pixel 2“)
joint PDF (blue) robust by MCF
correctedunwrapped
phasewrongambiguity(noise spikes)
unwrappedphase (2 BL)
ITP Dual (Multi)-Baseline Phase Unwrapping
Slide 12
Delta-k Interferometry for additional PU Support
CC
0
f2f
λ
Cλ
rΔ
SAR 2
SAR 1
Differential interferogram between 2 subbands at fC ± f0Generates interferogram with “carrier frequency” 2f0 << fCFor (150MHz) standard acquisitions: delta-k hamb ~ hamb x 96.5 (9.65 GHz / 100MHz)Phase unwrapping not necessary !Successfully tested with TS-X InSAR
(R. Brcic)
Salar de Uyuni, Standard 150MHz Stripmap 14.09/06.10.2007
Two 50 MHz bandwidth subbands.
3744 m/cycle 38.8 m/cycleheight of ambiguity > ~1500m variation in topography
scaling(wrapping)
Δk phase
ESA ITT 5509- A Novel Approach for Wide-Band SAR Interferometry
f_cf_0
ambiguous
unambiguous
Slide 13
Laser DEM: Gars am Inn, Bavaria5 km x 5 km, @ 5m res.
„TanDEM land“75 x 75 km
replication
Simulated TanDEM-X acquisitions (HELIX orbit, swathes, noise)
geometry simulation
Processing simulation setup
Amplitude, Layover,Shadow PhaseCoherence
InSAR simulation
resulting error map (1 – BL)
mean=0.95 mσ =1.57 m
PU errors
proc
essin
g
Dual Baseline PU
Slide 14
TanDEM-X PGS InSAR Processing Test Site “Salar de Arizaro” (Argentina)
stable, highly coherent area, several interferometric pairs in different geometries(A/D, overlapping beams) acquired.
July Dec ‘07:very few temporalchanges (in blue)!
Slide 15
TS-X InSAR: Single BaselinePhase UnwrappingChallenges
coherence: 0.85 baseline: 830 m !i = 39°
SRTM DEM
TS-X Interferogram (1)
height ambiguity: 7 m7 m
TS-X DEM (1)σ = 25cm !at 5m posting
……but with but with significantsignificantPU errorsPU errors
Slide 16
TerraSAR-X InSAR: 2nd Baseline coherence 2: 0.89baseline 2: 450 m > op. TanDEM-X baselinesTS-X 2nd pair
height ambiguity: 14 m14 m Differences 1st (7m hamb) – 2nd (14m hamb) DEM(atmosphere, baseline errors, fine structures, … &
PU errors in 1st DEM )
Slide 17
TanDEM-X Experimental Products:Co-registered SSCs
ITP
CoSSC
SSC (“TS-X L1b”)sat 1
SSC (“TS-X L1b”)sat 2
commoncomponents
DIMS PL: CoSSC.experimental Archive
EOWEBcatalogue orders:exp. CoSSCdelivery product
TanDEM-X acquisitionfor experimental product generation
xx
InSARprocessing forbistatic SM only (e.g. dual pol)
Slide 18
Experimental Products as Co-registered SSCsCoSSC structure and format corresponds to 2 TS-X SSC L1b products (minor modifications) plus common components and annotation
product performance strongly depends on acquisition conditions but is generally slightly reduced (w.r.t. TerraSAR-X mission products):
common swath may deviate / driftcommon bandwidth processing reduces resolutionbistatic channel not radiometricallycalibrated (best effort)no add. sidelobe suppression (Hamming = 1.0), …
… but:high geometric accuracycomprehensive annotation & co-registration allow straight-forward InSARprocessingmonostatic / active channel performance may be close to TS-X products
Slide 19
Summary I – Processing Chain
Processing chain optimized for systematic generation of all raw DEM data for global HRTI-3 DEM within 2.5 years.Uniform raw DEM data performance guaranteed (multiple coverage, reprocessing) Unified processing system ITP for
global DEMcustomized DEMsexperimental products (+ TMSP)
Bistatic SAR & InSAR - DEM processing has been successfully simulated for TanDEM-X conditionsSAR & InSAR processing capabilities tested with real TS-X data
Slide 20
Summary II - TanDEM-X Products
operational DEM products: see presentation by B. Wessel
operationally generated SAR products:experimental products from operational modes (co-registered complex images – “CoSSCs”)experimental mode raw data(processing with help from DLR contact scientist)TS-X mission basic products* from selected TanDEM-X raw data sets„byproduct“ of operational DEM processing chain:archive of CoSSCs from all acquisitions for DEM generation (multi-temporal global coverage)
*: TS-X basic product performance parameter specification does not apply