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PHOTOGRAMMETRY AND GEOINFORMATION TRENDS FOR LARGE SCALE MAPPING

PHOTOGRAMMETRY AND GEOINFORMATION TRENDS FOR LARGE SCALE MAPPING. Karsten Jacobsen Institute of Photogrammetry and GeoInformation University of Hannover jacobsen@ipi.uni-hannover.de. Large scale: 1 : 1000 – 1 : 5000 – (1 : 10 000)

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PHOTOGRAMMETRY AND GEOINFORMATION TRENDS FOR LARGE SCALE MAPPING

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  1. PHOTOGRAMMETRY AND GEOINFORMATION TRENDS FOR LARGE SCALE MAPPING Karsten Jacobsen Institute of Photogrammetry and GeoInformation University of Hannover jacobsen@ipi.uni-hannover.de

  2. Large scale: 1 : 1000 – 1 : 5000 – (1 : 10 000) definition large scale depending upon country and topic Mapping: mapping today = data acquisition for GIS in GIS location in national coordinates = scale independent but information contents corresponds to representation scale - usually only limited variation of representation scale (1 : 2) rules:accuracy: ~ 0.25mm in representation scale e.g. +/- 1.25m for 1 : 5000 +/- 0.25m for 1:1000 information contents: 0.05 – 0.1mm GSD in map scale GSD = ground sampling distance = distance between centres of neighboured pixels on ground e.g. for 1 : 5000 25cm – 50cm GSD for 1 : 1000 5cm – 10cm GSD Introduction

  3. Very clear trend to digital cameras Images for data acquisition DMC UltraCamD DSS DIMAC connection with GPS + IMU up to 4 independent cameras small format in flight direction

  4. DMC and UltraCamD with lower resolution of colour information (factor 4 – 5) high resolution colour images can be generated by pan-sharpening – lower resolution of colour corresponds to sensitivity of human eye red, green, blue, near infrared Applanix DSS – colour filter array output file grey values interpolated DIMAC – flexible combination of cameras Digital array cameras

  5. Information contents Photo from analogue camera resolution ~ 40 lp/mm ~80 pixels/mm 230mm format ~ 18 400 pixels DMC 43% in flight direction – compensated by number of images 76% across flight direction – compensated by better image quality UltraCamD 41% / 62% DSS 22% / 22% used with direct sensor orientation DIMAC 22% / 30% DSS and DIMAC economic only for small projects DMC can be compared with analogue photos – in flight direction more images, across the number of pixels correspond to 30 lp/mm – by the better quality of digital images (no film grain) this corresponds to analogue photos UltraCamD in flight direction 94% of DMC, across 82% but less expensive Digital array cameras – analogue cameras

  6. Accuracy Horizontal accuracy: SX = SY ~ 1/3 ground sample distance (GSD) image scale not important – only GSD e.g. swath width = 2.3km ( corresponds to analogue image scale 1:10 000) DMC GSD=16cm SX=SY~5cm UltraCamD GSD=20cm SX=SY~7cm analogue camera SX=SY~10cm (Sx’=10µm) Vertical accuracy: SZ = h/b * Spx Spx [GSD] ~ 1/3 GSD e.g. swath width = 2.3 km analogue camera wide angle: f=153mm DMC h/b=3.1 SZ~SX*3.1 = 15cm UltraCamD h/b=3.7 SZ~SX*3.7 = 26cm analogue camera SZ~SX*1.6 = 16cm (Spx=10µm) DMC: with same swath width like analogue camera: better horizontal, same vertical accuracy UltraCamD: better horizontal, less vertical accuracy (1:1.6) Digital array cameras – analogue cameras

  7. Digital line scan cameras Leica ADS40 f=62.5mm 4 colour bands with 12000 pixels 3 view directions panchromatic has to be connected to direct sensor orientation (GPS + IMU) from h=3km swath=3.75km pixel size on ground = 31cm pan: GSD=16cm (19cm) colour: GSD=31cm Staggered CCD-lines

  8. Company 3001 Inc, USA equipped with Z/I DMC and Leica ADS40 “ADS40 is an ortho-engine” - optimal conditions for the generation of ortho-images Z/I DMC used for mapping projects Imaging GSD 15cm – 2m with ADS40 (GSD of product) Imaging GSD 4cm – 15cm with DMC In general total project costs with digital cameras ~ 15% below costs for analogue cameras - no film, no film scanning, faster turn around, better image quality, no scratches Comparison digital array camera – digital line scan camera

  9. QuickBird panchromatic, 0.62m GSD can be used for mapping up to scale 1 : 5000 62cm GSD corresponds to scale of analogue aerial photos 1 : 50 000 2006 / 2007 with OrbView 5 and WorldView also 50cm GSG advantage of space images: not classified, homogenous accuracy – sub-pixel accuracy possible with few control points High resolution satellite image

  10. Traditional bundle block adjustment - higher number of control points Image orientation Combined adjustment with projection centre coordinates determined by relative kinematic GPS positioning  block with 5501 photos, with 22 control points full accuracy like with quite higher number of control points Direct sensor orientation relative kinematic GPS + inertial measurement unit (IMU) (gyros + accelerometer) GPS supports IMU, IMU supports GPS possible accuracy: 10cm – 20cm

  11. High effort in research, but limited operational use • Some progress in automatic building extraction based on large scale images • Project of University of Hannover in cooperation with mapping authority • verification of roads included in digital data base (ATKIS) against ortho-images • green lines verified, red lines have to be checked manually – support of operator • In general automatic object recognition not yet operational – will not be the case in the near future Automatic object recognition verified road, road to be checked blue = masked build up areas

  12. 1. Aerial photogrammetry – automatic image matching • 2. Laser scanning (LIDAR) • 3. Interferometric synthetic aperture radar (IfSAR) • Result = digital surface model DSM = height of visible surface (buildings, vegetation), problems in areas with poor contrast • can partially penetrate not so dense vegetation (first pulse, last pulse)  DSM, for vegetation partially bare ground, expensive method, but very detailed • Usually short wavelength (X-band, C-band) used, cannot penetrate vegetation IfSAR economic only for very large areas • In any case if DEM (height of bare ground) required, post-processing necessary, manually (time consuming) or by automatic filtering Digital Elevation Models (DEMs)

  13. Filtering DSM  DEM result of global filtering 1 iteration 3D-view of DSM from laser scanning

  14. SRTM-DEM Dubai SRTM C-band DEM By Shuttle Radar Topography Mission (SRTM) in 2000 DEM of world from 58° south – 60.25° north available with 3“ point spacing (92m at equator) DEMs available for handling fee 3D-view

  15. Accuracy of SRTM DEMs Accuracy of SRTM C-band DEMs against precise reference without bias for flat and open areas SZ ~ 2.6m - 3.7m

  16. displacement of railway dam in 2 neighboured ortho-images Ortho-images Ortho-image with overlaid lines from digital map not visible DEM Ortho-image – only correct location in height level of used DEM top of roof shifted, wall can be seen, parts of ground hidden top side

  17. True ortho-image uncorrected bridge True ortho-images do require a detailed DSM with height of all objects which shall be shown with correct position uncorrected bridges corrected bridges inserted from neighboured image Existing programs for generation of true ortho-images, main problem: expensive DSM, high overlap of images required – advantages of close to nadir view

  18. Very clear trend to digital cameras – advantages obvious digital array and digital line scan cameras will exist side by side, partially different applications growing application of high resolution space images Image orientation by direct sensor orientation will come, experience of companies required Reduction of DSM to DEM mainly automatic, only limited editing process generation of DEM based on aerial images, laser scanning and InSAR will exist side by side depending upon requirement rough DSM existing from SRTM-mission, sufficient for several applications True ortho-images still expensive – use limited to important parts like bridges Conclusion, summary

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