Comparison Of Elevation Collection Technologies
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Comparison Of Elevation Collection Technologies

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    Comparison Of Elevation Collection Technologies Comparison Of Elevation Collection Technologies Presentation Transcript

      • Flood modelling and management
      • Glasgow University
      • 8 September 2004
      • Paul Shaw - GeoVision
      • Format for morning session
      • 9-30 – 10.30 Comparison of modern data collection technologies
      • 10.30 – 10.45 Coffee
      • 10.45 – 11.45 Comparison of modern data collection technologies (cont)
      • 11.45 - 12.00 Coffee
      • 12.00 – 1.00 Remote sensing for environmental monitoring
      • 1.00 – 2.00 Lunch
      • How important are heights in flood modelling?
      • Comparison of data collection technologies
      • GPS - Global Positioning Systems
      • Aerial Photography
      • LIDAR - Light Detection and Ranging
      • SAR– Synthetic Aperture Radio Detection and Ranging
      • Multi Spectral Satellite Imagery
      • Comparison of data collection technologies
      • For each technology a summary on
      • Process of data collection
      • Potential sources of error
      • Benefits and concerns
      • General comments
      • Comparison of data collection technologies
      • GPS - Global Positioning Systems
      • Aerial Photography
      • LIDAR - Light Detection and Ranging
      • SAR– Synthetic Aperture Radio Detection and Ranging
      • Multi Spectral Satellite Imagery
      • GPS
      • Process
      • Use technique called RTK or kinematic
      • Requires base station and rover
      • Requires radio link
      • Software converts to grid and geoid heights
      • Collect mapping data (as points, polylines,polygons and attributes)
      • May require post-plotting using survey infill techniques
      • GPS
      • Potential sources of error
      • Grid transformation and geoid model – Link
      • Satellite azimuth, number, quality and spread (measured as DOP’s) - Link
      • Radio range
      • Base station problems
      • Benefits
      • Accurate to 10mm
      • Certainty with ground heights
      • Accurate definition of break lines
      • Data collected in useable format
      GPS
      • Concerns
      • Slow at 0.2 sq km/day
      • Not allowed in all countries
      • Radio strength
      • Foliage and infrastructure
      • No image
      • Access restrictions
      • GPS
      • General comments
      • Many UK companies - Link
      • In GB OS have active and passive stns – Link
      • OS trig and BM system redundant
      • NAVSTAR (US) – 29 operational at present - Link
      • GLONASS (Russian) - 8 operational at present – ( Link )
      • GALILEO (European) – operational from 2008 – 30 in total – ( Link )
      • Started becoming available in the mid nineties
      • Further details on how GPS works at ( Link )
      • Comparison of data collection technologies
      • GPS - Global Positioning Systems
      • Aerial Photography
      • LIDAR - Light Detection and Ranging
      • SAR– Synthetic Aperture Radio Detection and Ranging
      • Multi Spectral Satellite Imagery
      • Aerial Photography
      • Process
      • Route planning; weather forecasting; flying permission; possible pre-mark; control network
      • Film processing
      • Possible Scanning
      • Photo/Imagery control
      • Aerial triangulation
      • DEM generation; possible vector digitising; post plotting; integration
      • Ortho production/mosaicing
      • Aerial Photography
      • Potential sources of error
      • Crabbing, fore and aft overlap
      • Lens calibration
      • Film quality
      • Verticality
      • Scale problems through large terrain change
      • Forward Motion
      • Photo control errors
      • Concerns
      • Flying permission required
      • Seasonal
      • Weather dependency
      • Heights to top of foliage
      • Restrictions by government
      • Matching of orthos
      • Automated DEM’s
      Aerial Photography
      • Benefits
      • Large areas covered in one flight
      • Height generated from the imagery
      • Infrared available
      • Orthophotos
      • 3D visualisations
      • Automated DEM’s
      • Aerial Photography
      • General comments
      • Was used by the EA – replaced by LIDAR in 1998
      • Increasingly sophisticated on-board systems
      • Approx 10 UK companies
      • Fixed Wing or helicopter, hard copy or digital
      • Large archive at larger scales through BKS, Simmons Aerofilms, OS, OSNI and others
      • Getmapping have GB covered at 1:10,000 – Link Imagery £25 per sq km at 1:10,000 scale, heights extra
      • Comparison of data collection technologies
      • GPS - Global Positioning Systems
      • Aerial Photography
      • LIDAR - Light Detection and Ranging
      • SAR– Synthetic Aperture Radio Detection and Ranging
      • Multi Spectral Satellite Imagery
      • LIDAR
      • LIDAR
      • Process
      • Route planning; weather forecasting; flying permission; control network
      • Processing – last reflection
      • DEM generation;
      • Post survey infill
      • Integration
      • LIDAR
      • Potential sources of error include
      • GPS and IMU calibration
      • IMU and laser head calibration
      • Lazer pulse rate
      • GPS baseline length
      • Level of uncertainty with ground height
      • No break line definition
      • Details available at ( Link )
      • Benefits
      • Accurate to 50mm
      • Large areas covered in one flight (30 sq km in one hour)
      • Can be flown at night
      • Not dependent on sun
      • Water height
      LIDAR
      • Concerns
      • No image
      • Weather dependency
      • Flying permission required
      • Processing time – up to 4 months for a few days data collection
      • LIDAR
      • General comments
      • 4 UK companies – global directory at ( Link )
      • QinetiQ have combined with digital cameras to create ATLAS system – ( Link )
      • General information about LIDAR can be found at ( Link and Link )
      • Used extensively by the EA - archive coverage - Link . Catalogue - Link
    •  
      • Coffee break
      • Comparison of data collection technologies
      • GPS - Global Positioning Systems
      • Aerial Photography
      • LIDAR - Light Detection and Ranging
      • SAR– Synthetic Aperture Radio Detection and Ranging
      • Multi Spectral Satellite Imagery
      • SAR
      • Process (InterMap)
      • Aircraft has 2 antennae, receive slightly different return signals, phase difference determines height
      • Synthetic aperture digitally enhances the data in real time
      • Rigorous QC processing checks
      • DEM
      • DSM by interpolation
      • Intermap SAR description at ( Link )
      • SAR
      • Potential sources of error
      • Shadow
      • Rain shadow
      • S ignal saturation
      • Missing data
      • Specular reflection
      • DSM generation
      • Details at ( Link )
      • Benefits
      • Can cover 100 sq km in a few hours
      • Generates height (up to 0.3m) and image (up to 2.5m)
      • All weather capability
      SAR
      • Concerns
      • Flying permission required
      • Gives height to first reflection
      • Accuracy of DSM
      • No break lines - Nextmap products are 5 and 10m grid spacing
      • SAR
      • General comments
      • No UK companies
      • Accuracy comparison by EA available at ( Link )
      • Nextmap data for UK has 2 accuracy levels – 0.6m for the SE and 1.5m for the rest
      • QinetiQ have just gained reseller status
      • Nextmap archive at Link
      • Intermap global archive and prices at Link
      • Comparison of data collection technologies
      • GPS - Global Positioning Systems
      • Aerial Photography
      • LIDAR - Light Detection and Ranging
      • SAR– Synthetic Aperture Radio Detection and Ranging
      • Multi Spectral Satellite Imagery
      • Multi Spectral Satellites Imagery
      • Process
      • Order and collect basic imagery
      • Image control points
      • Rectification
      • DEM generation
      • Possible vector digitising
      • Map completion
      • Multi Spectral Satellites Imagery
      • Potential sources of error
      • Cloud
      • Other atmospheric interference
      • Off-nadir angle of separate image
      • Sun
      • Shadow
      • Incorrect sensor calibration details
      • Multi Spectral Satellites Imagery
      • Benefits
      • No restrictions
      • Large archives
      • Large area coverage
      • Repeatability
      • Concerns
      • Problems with automated DEM’s
      • Weather dependency
      • Heights to top of foliage/buildings
      • Height accuracy still at research stage
      • Satellites
      • General comments
      • Wide range of sensors with stereo capability
      • On-going program of launch of new satellites
      • Quickbird ( Link ), IKONOS ( Link ), SPOT ( Link ), IRS ( Link ).
      • Recent research by a Japanese University has shown 0.5m height accuracy possible – Link
      • Quickbird archive at Link
    •  
    •  
    •  
      • Comparison
      50cm 50 days new Min 100 sq km £0.03k Quickbird 30cm Global archive £0.064k (Hts only) SAR 15cm 120 days new GB archive £0.35k LIDAR (No image) 4cm 50 days new Global archive £3-5k Aerial Photography 1cm 50 days/sq km new £5-10k GPS (No image) Accuracy Delivery Cost/sq km Technology
      • Summary
      • There is an increasing amount of height data for flood modelling. The skill is to select the correct one for a given application. Considerations include:-
      • How accurate do you want the heights?
      • How regular do you want it monitored?
      • What intensity of information do you want?
      • How much money have you got?
      • How quickly do you want it?
      • but.................
      • Other considerations
      • Global warming – 10 - 20cm msl rise last century, estimated 50 cm this century - ( Link )
      • Glacial Isostatic Adjustment – 2 mm per annum (- in South, + in North) – ( Link ). General Info at ( Link )
      • OS recently adjusted UK geoid – up to 10cm variance
      • Spring tides – up to 12m range - ( Link and Link )
      • Tidal loading – up to 6cm variance in 1 day
    •  
      • Coffee break