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Contributions from: David Small, Erich Meier, Adrian Schubert, Urs Krüttli, Daniel Nüesch (RSL)

ASAR Calibration Review IMG - Geocoded Products Geometric Performance of IM Products. Contributions from: David Small, Erich Meier, Adrian Schubert, Urs Krüttli, Daniel Nüesch (RSL) Hannes Raggam, Wolfgang Hummelbrunner, Martina Franke (Joanneum Research),

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Contributions from: David Small, Erich Meier, Adrian Schubert, Urs Krüttli, Daniel Nüesch (RSL)

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  1. ASAR Calibration Review IMG - Geocoded Products Geometric Performance of IM Products • Contributions from: • David Small, Erich Meier, Adrian Schubert, Urs Krüttli, Daniel Nüesch (RSL) • Hannes Raggam, Wolfgang Hummelbrunner, Martina Franke (Joanneum Research), • Detlev Kosmann (DLR), Mauro Pirri (Telespazio)

  2. Test localisation accuracy of ellipsoid-geocoded IMG and other IM products Approach for IMG Products: Measure ground control points (GCPs) in IMG (UTM) Measure topomap GCPs (e.g. Dutch Oblique Stereographic) Convert points to common geometric reference Compare locations; summarise statistical differences Objectives

  3. Flevoland, The Netherlands IMG orbit 2130 IS3 VV UTM projection TopoMaps: 1:25000, 1:50000 Dutch Oblique Stereographic Coordinate conversion, comparison: Offset statistics: Easting: -262.3±71.9 [m] Northing: 33.9±53.6 [m] Causes for poor results: predicted orbit used during processing shifted chirp replica in range compression IMG Localisation Accuracy

  4. Edam: ISLR= -9.44dB<-7dB(-12+5), PSLR=-16.57<-15dB(-20+5),3dB width=25.9m x 22.3m (<33m) Swifterbant: ISLR= -7.77dB<-7dB(-12+5), PSLR= -17.96<-15dB(-20+5), 3dB width=23.9m x 21.7m (<33m) IMG 2130 IS3 VV Radiometric Performance (bilinear resampling)

  5. Approach: Geolocation Integrate orbit state vectors & digital elevation model (DEM) Solve Range & Doppler equations for each point in DEM Resample radar image (IMS, IMP, etc.) into DEM map geometry Accuracy Statistics Locate map ground control points (GCPs) in geolocated image Statistical analysis of differences between locations measured from map and image IMS, IMP, IMM, WSM Localisation

  6. Corner Reflectors oriented for next beam, ascending/descending orbit based on acquisition plan CRs have been reoriented ~18 times per orbit cycle since 2002.05.15 Dübendorf, Emmen, Payerne (Switzerland): Bern-Zürich Corner Reflectors

  7. Two “FP” IMS products from Flevopolder ASA_IMS_1PXPDE20020727_211634_000000152008_00072_02130_0002.N1 ASA_IMS_1PXPDE20020730_095910_000000162008_00108_02166_0003.N1 Localisation test via Ellipsoid Geocoded ascending/descending overlay IMS Localisation Results

  8. Format, Visual Inspection, Annotation ok. !! Predicted Orbit !! Control point 3 X (UTM) Y (UTM) Reference from map 679503.82 5805880.27 27072002eec_8b.img (blue) 679836.02 5805945.27 30072002eec_8b.img (green) 679318.11 5805938.71 Diff. Map - 27072002 -332.20 -65.00 Diff. Map - 30072002 185.71 -58.44 Diff. 27072002 - 30072002 517.91 6.56 IMS Flevoland Overlay

  9. IMP: 2130 IS3 (asc) IMS: 2166 IS3 (desc) IMS & IMP Flevoland: Predicted FP Orbits, Chirp Replica A-Priori Localisation Easting: -126.6±19.3m Northing: -19.3±13.7m Easting: 169.5±11.9m Northing: -40.5±10.1m

  10. IMS: 670 IS4 (asc) IMS: 706 IS2 (desc) IMS Flevoland Overlay, Restituted FR Orbits, Chirp Replica A-Priori Localisation Easting: -121.6±17.6m Northing: -58.3±13.5m Easting: 135.6±12.7m Northing: -21.1±10.8m Predicted vs. Restituted: Similar Result

  11. IMS: 670 IS4 (asc) IMS: 706 IS2 (desc) IMS Flevoland Geolocation: Predicted Orbits & Nominal Chirp A-Priori Localisation Easting: -79.2±18.6m Northing: -57.9±12.6m Easting: 84.5±12.6m Northing: 2.8±13.7m Error almost halved with nominal chirp vs. replica

  12. GLOBE “terrain”-geocoding for 2 IMS images, orbits 670 & 706 East/West difference ~160m (250m for FR/chirp replica pair) N.B. error doubled through overlay Flevoland Ascending/Descending Image Overlay

  13. Required swath width does not decrease monotonically with incidence angle All products tested so far have passed minimum swath width test Swath Width Requirements

  14. A-Priori Location Accuracy: Mean offsets Garmisch-Partenkirchen, Germany

  15. Multiple Slices Orbit state vectors: irregular spacing accounted for in software Multiple ground/slant range polynomials integrated into geocoding procedure not yet in geometry refinement Geographic Coordinates 55 54 53 52 Latitude 51 50 49 48 -2 -1 0 1 2 Longitude IMM, WSM: Medium Resolution Stripline Products

  16. ScanSAR beam boundaries visible; quality flag incorrectly set for initial null lines Terrain geocoding using GLOBE 1km DEM Accuracy assessment only possible piecemeal Multiple datum shifts add further source of GCP error Width Swath Mode: Central Europe 1st Test Image Colour cycle 2000m Accuracy assessment in progress

  17. More accurate datum shifts recently propagated to partners for NL, DE, AT. NL: AT: DE: Cartographic & Geodetic Parameters

  18. Localisation significantly improved using nominal chirp rather than chirp replica (preliminary results based on comparison of two Flevoland pairs) accuracy similar for predicted & restituted orbits extremely large errors for some “Garmisch”-scenes (JR: up to 15km!) sign of error changes for ascending/descending systematic to radar geometry more scenes/beams/modes processed with nominal chirp required for definitive accuracy conclusions timetable for improved orbit quality? WSM product: quality flag problem localisation accuracy assessment in progress Conclusions

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