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High-Speed High-Density Data Acquisition in Airborne Laser Scanning Applications

High-Speed High-Density Data Acquisition in Airborne Laser Scanning Applications. INTER GEO September 2011, Nürnberg Peter Rieger Andreas Ullrich RIEGL LMS GmbH. Contents: Range ambiguities in time-of-flight measurements Known measures in resolving or avoiding range ambiguities

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High-Speed High-Density Data Acquisition in Airborne Laser Scanning Applications

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  1. High-Speed High-Density Data Acquisition in Airborne Laser Scanning Applications INTERGEO September 2011, Nürnberg Peter Rieger Andreas Ullrich RIEGL LMS GmbH www.riegl.com

  2. Contents: • Range ambiguities in time-of-flight measurements • Known measures in resolving or avoiding range ambiguities • Advantages and disadvantages • Introduction to RIEGL’s novel approach RIEGL Laser Measurement Systems www.riegl.com

  3. Airborne laser scanning is a rapid, highly accurate and efficient method of capturing 3D data of large areas. for planes: LMS-Q680i / LMS-Q560 • Multiple-Time-Around (MTA) Processing (LMS-Q680i) • Full Waveform Analysis for an unlimited number of target echoes • operating flight altitude up to 5,000 / 3,300 ft AGL • Laser PRR 400 / 240 kHz for helicopters: NEWRIEGL VQ-580 • optimized for glacier and snow measurements RIEGL VQ-480 / VQ-380 • echo digitization and Online Waveform Processing • multiple target capability • operating flight altitude up to 2,500 / 1,800 ft AGL www.riegl.com Airborne Laser Scanning

  4. Sm Sm+1 Amplitude En Tm Tn Tm+1 Time www.riegl.com Principle of time-of-flight measurements

  5. Definition of „Multiple-Time-Around“ from the “IEEE Standard Radar Definitions, IEEE Std 686-1997 (1998)”: www.riegl.com

  6. MTA Zone 1 Sm-3 Sm-2 Sm-1 Sm Sm+1 Amplitude En-1 En-3 En En-2 Tm-3 Tn-3 Tm-2 Tn-2 Tm-1 Tn-1 Tm Tn Tm+1 Time rm-3,MTA1 rm-2,MTA1 rm,MTA1 rm-1,MTA1 MTA Zone 1: www.riegl.com

  7. MTA Zone 2 Sm-3 Sm-2 Sm-1 Sm Sm+1 Amplitude En-1 En-3 En En-2 Tm-3 Tn-3 Tm-2 Tn-2 Tm-1 Tn-1 Tm Tn Tm+1 Time MTA Zone 2: rm-3,MTA2 rm-2,MTA2 rm-1,MTA2 www.riegl.com

  8. MTA Zone 3 Sm-3 Sm-2 Sm-1 Sm Sm+1 Amplitude En-1 En-3 En En-2 Tm-3 Tn-3 Tm-2 Tn-2 Tm-1 Tn-1 Tm Tn Tm+1 Time MTA Zone 3: rm-4,MTA3 rm-3,MTA3 rm-2,MTA3 www.riegl.com

  9. MTA Zone 4 Sm-3 Sm-2 Sm-1 Sm Sm+1 Amplitude En-1 En-3 En En-2 Tm-3 Tn-3 Tm-2 Tn-2 Tm-1 Tn-1 Tm Tn Tm+1 Time MTA Zone 4: rm-5,MTA4 rm-4,MTA4 rm-3,MTA4 www.riegl.com

  10. MTA Zone 1, 2, 3 or 4 ? Sm-3 Sm-2 Sm-1 Sm Sm+1 Amplitude En-1 En-3 En En-2 Tm-3 Tn-3 Tm-2 Tn-2 Tm-1 Tn-1 Tm Tn Tm+1 Time MTA 1 MTA 2 ? rm,MTA1 MTA 3 rm-1,MTA2 MTA 4 rm-2,MTA3 rm-3,MTA4 www.riegl.com

  11. Maximum unambiguous range vs. pulse repetition rate Maximum unambiguous measurement range Ru [m] Ru=375m @ 400kHz x Pulse repetition rate [kHz] www.riegl.com

  12. Known methods in avoiding range ambiguities: • careful choice of operating altitudes • Spatial multiplexing:  2 x RIEGL LMS-Q680i • Wavelength multiplexing: RIEGL VQ-820-G (532nm), RIEGL VQ-580 (1064nm) Known methods in resolving range ambiguities: • Spatial analysis based on known distance (RiANALYZE) www.riegl.com Methods in avoiding or resolving range ambiguities

  13. Avoiding range ambiguities in flight planning MTA zone 1 MTA zone 2 MTA zone 3 www.riegl.com

  14. Avoiding range ambiguities in flight planning www.riegl.com

  15. Spatial Multiplexing Spatial separation by scanner orientation Spatial separation by mirror synchronization 1PPS typ. > 1 deg typ. > 10 deg deam divergence typ. < 0.5 mrad www.riegl.com

  16. Wavelength multiplexing Wavelength multiplex by using 2+ wavelengths 532 nm 1064nm 1550 nm VQ-820G VQ-580 Q-680i www.riegl.com

  17. Resolving range ambiguities by spatial analysis www.riegl.com

  18. Advantages and Disadvantages www.riegl.com

  19. New approach, Step 1: Variation of pulse repetition intervals Sm Sm+1 Sm+2 Sm+3 Sm+4 Amplitude En+2 En+3 En En+1 Time Tm Tn Tm+1 Tn+1 Tm+2 Tn+2 Tm+3 Tn+3 Tm+4 Δtm+2 Δtm+2 Δtm+1 Δtm+1 Δtm+3 Δtm+3 Δtm+4 Δtm+4 τ = PRR-1 τ = PRR-1 τ τ τ τ τ τ rm+2,MTA1 rm,MTA1 rm+1,MTA1 rm+3,MTA1 rm,MTA2 = rtrue rm+1,MTA2 = rtrue rm+2,MTA2=rtrue www.riegl.com

  20. New approach, Step 2: Analysis of the influence of PRI jitter  www.riegl.com

  21. RIEGL VQ-580 online waveform processing airborne laser scanner RiMTA automated range ambiguity resolution RIEGL LMS-Q680i full waveformairborne laser scanner www.riegl.com RiMTA

  22. One scan stripe transits 3 MTA Zones RIEGL LMS-Q680i PRR = 400kHz Ru = 375m 1000 MTA 3 900 800 700 MTA 2 600 500 Alt AGL [m] 400 MTA 1 300 200 0 20 40 60 80 100 120 140 t [s] www.riegl.com

  23. RIEGL LMS-Q680i PRR = 400kHz Ru = 375m 1000 MTA 3 900 800 700 MTA 2 600 500 Alt AGL [m] 400 MTA 1 300 200 0 20 40 60 80 100 120 140 t [s] www.riegl.com One scan stripe transits 3 MTA Zones

  24. RIEGL LMS-Q680i PRR = 400kHz Ru = 375m 1000 MTA 3 900 800 700 MTA 2 600 500 Alt AGL [m] 400 MTA 1 300 200 0 20 40 60 80 100 120 140 t [s] www.riegl.com One scan stripe transits 3 MTA Zones

  25. RIEGL LMS-Q680i PRR = 400kHz Ru = 375m 1000 MTA 3 900 800 700 MTA 2 600 500 Alt AGL [m] 400 MTA 1 300 200 0 20 40 60 80 100 120 140 t [s] www.riegl.com One scan stripe transits 3 MTA Zones

  26. RIEGL LMS-Q680i PRR = 400kHz Ru = 375m 1000 MTA 3 900 800 700 MTA 2 600 500 Alt AGL [m] 400 MTA 1 300 200 0 20 40 60 80 100 120 140 t [s] www.riegl.com One scan stripe transits 3 MTA Zones

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