High-Speed High-Density Data Acquisition in Airborne Laser Scanning Applications INTERGEO September 2011, Nürnberg Peter Rieger Andreas Ullrich RIEGL LMS Gmb. H www. riegl. com
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 www. riegl. com RIEGL Laser Measurement Systems
Airborne laser scanning is a rapid, highly accurate and efficient method of capturing 3 D data of large areas. for planes: LMS-Q 680 i / LMS-Q 560 • Multiple-Time-Around (MTA) Processing (LMS-Q 680 i) • 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 k. Hz www. riegl. com for helicopters: NEW RIEGL 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 Airborne Laser Scanning
Amplitude Sm En Tm www. riegl. com Sm+1 Tn Tm+1 Time Principle of time-of-flight measurements
from the “IEEE Standard Radar Definitions, IEEE Std 686 -1997 (1998)”: www. riegl. com Definition of „Multiple-Time-Around“
Amplitude MTA Zone 1: Sm-3 Sm-2 Sm-1 En-3 Tm-3 En-2 Tn-3 Tm-2 Tn-2 Tm-1 rm-3, MTA 1 www. riegl. com rm-2, MTA 1 Sm En Tn-1 Tm rm-1, MTA 1 Sm+1 Tn Tm+1 Time rm, MTA 1 MTA Zone 1
Amplitude MTA Zone 2: Sm-3 Sm-2 Sm-1 En-3 Tm-3 En-2 Tn-3 Tm-2 Tn-2 Tm-1 Sm En-1 Tm Sm+1 En Tn Tm+1 Time rm-3, MTA 2 rm-2, MTA 2 rm-1, MTA 2 www. riegl. com MTA Zone 2
Amplitude MTA Zone 3: Sm-3 Sm-2 Sm-1 En-3 Tm-3 Sm En-2 Tn-3 Tm-2 Tn-2 Tm-1 Tn-1 Tm Sm+1 En Tn Tm+1 Time rm-4, MTA 3 rm-3, MTA 3 rm-2, MTA 3 www. riegl. com MTA Zone 3
Amplitude MTA Zone 4: Sm-3 Sm-2 Sm-1 En-3 Tm-3 En-2 Tn-3 Tm-2 Tn-2 Tm-1 Sm En-1 Tm Sm+1 En Tn Tm+1 Time rm-5, MTA 4 rm-4, MTA 4 rm-3, MTA 4 www. riegl. com MTA Zone 4
Amplitude Sm-3 Sm-2 Sm-1 Sm Sm+1 MTA 1 En-3 Tm-3 En-1 En-2 Tn-3 Tm-2 MTA 2 Tn-2 Tm-1 ? En Tn-1 Tm Tn Tm+1 Time rm, MTA 1 MTA 3 rm-1, MTA 2 rm-2, MTA 3 MTA 4 rm-3, MTA 4 www. riegl. com MTA Zone 1, 2, 3 or 4 ?
![Maximum unambiguous measurement range Ru [m] Ru=375 m @ 400 k. Hz x Pulse](https://present5.com/presentation/19d4e74cd8790855a4f85af5ab9a8fa7/image-11.jpg "Maximum unambiguous measurement range Ru [m] Ru=375 m @ 400 k. Hz x Pulse")
Maximum unambiguous measurement range Ru [m] Ru=375 m @ 400 k. Hz x Pulse repetition rate [k. Hz] www. riegl. com Maximum unambiguous range vs. pulse repetition rate
Known methods in avoiding range ambiguities: ● ● ● careful choice of operating altitudes Spatial multiplexing: 2 x RIEGL LMS-Q 680 i Wavelength multiplexing: RIEGL VQ-820 -G (532 nm), RIEGL VQ-580 (1064 nm) Known methods in resolving range ambiguities: ● Spatial analysis based on known distance (Ri. ANALYZE) www. riegl. com Methods in avoiding or resolving range ambiguities
MTA zone 1 MTA zone 2 MTA zone 3 www. riegl. com Avoiding range ambiguities in flight planning
www. riegl. com Avoiding range ambiguities in flight planning
Spatial separation by scanner orientation Spatial separation by mirror synchronization 1 PPS typ. > 1 deg deam divergence typ. < 0. 5 mrad www. riegl. com typ. > 10 deg Spatial Multiplexing
Wavelength multiplex by using 2+ wavelengths 532 nm 1550 nm VQ-820 G www. riegl. com 1064 nm VQ-580 Q-680 i Wavelength multiplexing
www. riegl. com Resolving range ambiguities by spatial analysis
Method Advantages Disadvantages Complex and dangerous in difficult terrain Flight Planning Spatial multiplexing Overall pulse repetition rate doubled Doubling sales for manufacturer Wavelength multiplexing Additional attributes for target classification, e. g. , vegetation indices +1 scanner → only +1 Ru Higher investment for customer Irregular point pattern Complex system Spatial data analysis Algorithms adaptable to application Tuning of algorithms if neccessary apriori knowledge of terrain required www. riegl. com Advantages and Disadvantages
Amplitude Sm Sm+1 Sm+2 En Tn+1 τ = PRR-1 rm, MTA 1 Tm+2 Tn+2 Δtm+1 τ rm+1, MTA 1 Sm+4 En+2 En+1 Tn Tm+1 Tm Sm+3 τ rm+2, MTA 1 En+3 Time Tn+3 Tm+4 Tm+3 Δtm+4 τ rm+3, MTA 1 rm, MTA 2 = rtrue rm+1, MTA 2 = rtrue www. riegl. com rm+2, MTA 2=rtrue New approach, Step 1: Variation of pulse repetition intervals
www. riegl. com New approach, Step 2: Analysis of the influence of PRI jitter
RIEGL LMS-Q 680 i RIEGL VQ-580 Ri. MTA full waveform airborne laser scanner online waveform processing airborne laser scanner automated range ambiguity resolution www. riegl. com Ri. MTA
RIEGL LMS-Q 680 i PRR = 400 k. Hz Ru = 375 m 1000 MTA 3 Alt AGL [m] 900 800 700 MTA 2 600 500 400 MTA 1 300 200 0 www. riegl. com 20 40 60 80 t [s] 100 120 140 One scan stripe transits 3 MTA Zones
RIEGL LMS-Q 680 i PRR = 400 k. Hz Ru = 375 m 1000 MTA 3 Alt AGL [m] 900 800 700 MTA 2 600 500 400 MTA 1 300 200 0 www. riegl. com 20 40 60 80 t [s] 100 120 140 One scan stripe transits 3 MTA Zones
RIEGL LMS-Q 680 i PRR = 400 k. Hz Ru = 375 m 1000 MTA 3 Alt AGL [m] 900 800 700 MTA 2 600 500 400 MTA 1 300 200 0 www. riegl. com 20 40 60 80 t [s] 100 120 140 One scan stripe transits 3 MTA Zones
RIEGL LMS-Q 680 i PRR = 400 k. Hz Ru = 375 m 1000 MTA 3 Alt AGL [m] 900 800 700 MTA 2 600 500 400 MTA 1 300 200 0 www. riegl. com 20 40 60 80 t [s] 100 120 140 One scan stripe transits 3 MTA Zones
RIEGL LMS-Q 680 i PRR = 400 k. Hz Ru = 375 m 1000 MTA 3 Alt AGL [m] 900 800 700 MTA 2 600 500 400 MTA 1 300 200 0 www. riegl. com 20 40 60 80 t [s] 100 120 140 One scan stripe transits 3 MTA Zones
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