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IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
IGARSS2011_Gustavsson_v3.ppt
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IGARSS2011_Gustavsson_v3.ppt

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  • 1. Detection of Wind-Thrown Trees in VHF/UHF SAR Images Johan Fransson, Andreas Pantze Swedish University of Agricultural Sciences (SLU) Anders Gustavsson, Lars Ulander Swedish Defence Research Agency (FOI) IGARSS – Beyond the Frontiers: Expanding our Know-ledge of the World, Vancouver, Canada, 25-29 July 2011
  • 2. Outline
    • Goals
    • SAR systems
    • Test site
    • Experiment set-up
    • Flight program
    • Detection of wind-thrown single trees
    • Summary
    IGARSS 2011
  • 3. Goals
    • Develop and evaluate methods for large-scale mapping and monitoring of wind-thrown forest
    • Use the methodology operationally
    IGARSS 2011
  • 4. VHF SAR system: CARABAS-II
    • Platform: Sabreliner aircraft
    • Frequency band: 20 - 90 MHz, HH
    • SAR-mode
    • Resolution: 2.5 m x 2.5 m
    • Imaging: Looking left and right simultaneuosly possible (”ping- pong” mode)
    IGARSS 2011 Photo: Pia Ericson, FMV
  • 5. UHF SAR system LORA
    • Platform: Sabreliner aircraft
    • Frequency band: 200 - 800 MHz, HH
    • Left antenna boom: 200-400 MHz
    • Right antenna boom: 400-800 MHz
    • SAR-mode
    • Resolution: 0.3 m x 0.3 m
    • Imaging: Looking left only
    IGARSS 2011 Photo: Pia Ericson, FMV
  • 6. Test site – Remningstorp IGARSS 2011 ALOS PALSAR image: Copyright JAXA
  • 7. Experiment set-up Wind-thrown single trees
    • Located on open field
    • 25 spruce trees
    • Three diameters – 15, 20, and 25 cm
    • Three directions – 80 ° , 91 ° , and 102 °
    • Tree root uplifted about 1 m above ground
    • Prepared in late summer 2006
    IGARSS 2011
  • 8. Example of wind-thrown single tree IGARSS 2011 Simulated wind-thrown single tree positioned on an open field with the root end uplifted (here with a breast height diameter of 25 cm and a trunk direction of 80°)
  • 9. Layout on the open field IGARSS 2011 Diameter in breast height (cm) Area: 200×300 m 2 Tree direction (degree) Area: 200×300 m 2
  • 10. Flight program to map experiment set-up IGARSS 2011
    • CARABAS-II looking right, 20-82MHz
    • LORA looking left, 222-474 MHz
    • Eight headings separated by 45 °
    • One heading 22.5 ° in between two others
    • Nine headings:
      • 35 °/ 215 °, 80 °/ 260 °, 125 °/ 305 ° and 170 °/ 215 °
      • 102° (CARABAS-II) or 282 ° (LORA)
    • Three imaging passes repeated in a mission
  • 11. Flight program to map experiment set-up IGARSS 2011
    • Headings aligned to tree directions:
      • 80 °/ 260 °, all three dbh values
      • 102° or 282 °, 25 cm dbh only
      • Tree direction 91° (25 cm dbh only) is 11° off closest flight headings
    • SAR data acquisition repeated two times:
      • 28 September 2006 and 20 February 2007 for CARABAS-II
      • 9 November 2006 and 5 March 2007 for LORA
  • 12. Flight program to map experiment set-up IGARSS 2011 CARABAS-II (ping-pong mode) Radar aim point @ p2 Labels at start of registration LORA
  • 13. Layout on the open field IGARSS 2011 Diameter in breast height (cm) Area: 200×300 m 2 Tree direction (degree) Area: 200×300 m 2
  • 14. CARABAS-II 2006 - Image chips r06_2_10 r06_2_1 r06_2_ 3 r06_2_ 8 r06_2_ 4 r06_2_ 9 r06_2_ 7 r06_2_ 2 r06_2_1 1 35° / 125° 215° / 305° 80° / 170° 260° / 350° 125° / 215° 170° / 260° 350° / 80° 305° / 35° 102° / 192° 200 m 300 m IGARSS 2011 xxx° = Flight heading yyy° = Illumination direction
  • 15. LORA 2006 - Image chips r06_ 3 _ 5 r06_ 3 _ 9 r06_ 3 _ 4 r06_ 3 _ 6 r06_ 3 _ 7 r06_ 3_11 r06_ 3 _ 12 r06_ 3 _ 8 215° / 125° 35° / 305° 260° / 170° 80° / 350° 305° / 215° 350° / 260° 170° / 80° 125° / 35° r06_ 3 _ 3 282° / 192° 200 m 300 m xxx° = Flight heading yyy° = Illumination direction IGARSS 2011
  • 16. Results – single trees IGARSS 2011 Breast Height Diameter (cm) CARABAS-II Images Acquired in 2006 (12 passes including repeated headings) Difference between trunk direction and flight heading (°) Number of trees Number of trees visible in imagery Proportion of trees visible in imagery (%) 15 0 20 0 0 22 5 0 0 45 20 0 0 90 15 0 0 20 0 20 16 80 22 5 4 80 45 20 0 0 90 15 0 0 25 0 25 25 100 11 25 24 96 22-23 35 14 40 34 10 2 20 45 20 0 0 56 10 0 0 67-68 25 0 0 79 15 0 0 90 15 0 0
  • 17. Results – single trees IGARSS 2011 Breast Height Diameter (cm) LORA Images Acquired in 2007 (12 passes including repeated headings) Difference between trunk direction and flight heading (°) Number of trees Number of trees visible in imagery Proportion of trees visible in imagery (%) 15 0 15 15 100 22 5 5 100 45 30 0 0 90 10 0 0 20 0 15 15 100 22 5 5 100 45 30 0 0 90 10 0 0 25 0 20 20 100 11 20 20 100 22-23 35 35 100 34 15 13 87 45 30 0 0 56 15 0 0 67-68 25 0 0 79 10 0 0 90 10 0 0
  • 18. 2007 results – single trees IGARSS 2011
    • The same number of trees was detected visually in LORA images
    • The number of trees detected visually in the CARABAS-II images was slightly reduced
    r06_ 3 _ 3 282° / 192° LORA 2006 r0 7 _ 2 _ 3 282° / 192° LORA 2007 r06_ 2 _ 11 102° / 192° CARABAS-II 2006 r0 7 _ 1 _ 11 102° / 192° CARABAS-II 2007
  • 19. Summary
    • To detect wind-thrown single trees under ideal conditions using CARABAS-II (VHF), the breast height diameter must exceed 15 cm and the deviation between the trunk direction and flight heading should be less than 22°
    • In the LORA (UHF) case, all trees with a deviation between the trunk direction and flight heading equal to or less than 22° were visible, independent of tree size investigated
    IGARSS 2011
  • 20. Summary (cont.)
    • The ability to detection wind-thrown single trees in 2007 were equally good for LORA, but the number of trees visible in imagery for CARABAS was slightly lower
    • The visible single trees in the LORA images appeared more distinct than in the CARABAS-II images, i.e. more pronounced elongated features as a result of the higher resolution
    IGARSS 2011
  • 21. Summary (cont.)
    • Based on visual interpretation, it is likely that the detection of wind-thrown forests could be improved using VHF/UHF SAR images acquired both prior to and after a storm event by applying change detection algorithms
    IGARSS 2011

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