1. Morphological measurement using close range photogrammetry- guidance from ISPRS V6 Jim Chandler 1, Rene Wackrow 1 and Dirk Rieke-Zapp 2 1 Loughborough University, UK 2 University of Berne, Switzerland j.h.chandler@lboro.ac.uk AAG, Seattle- April 2011 (with notable input from: Tom Dijkstra, Simon Buckley, Marko Tuominen, Stephen Bird and members of ISPRS Working Group V6)

2. Overview  Why produce “tips”?  Who contributed?  Key points?  An illustration! AAG, Seattle- April 2011

3. Why are “tips” necessary?  Stated activity!  Past experiences- particularly postgraduates seeking advice  Two sets! AAG, Seattle- April 2011  Stated activity!  Past experiences- particularly postgraduates seeking advice  Two sets!

4. Who contributed? AAG, Seattle- April 2011  Primarily WG Officers  Also notable input from industry! including: Marko Tuomien, Datapix Pty Ltd, Queensland, Australia Stephen Bird, Fluvial Systems Research Inc, Whiterock, Canada

5. Start simple- start small!  150 small format images of a river channel in Spain- I fly next week and my supervisor doesn’t know about photogrammetry! AAG, Seattle- April 2011  Common sense!  Familiarisation- techniques and how software works!  Start with:  Small test area captured with perhaps two pairs  Ideally use a pre-calibrated camera  Establish abundant photo control- easy restitution plus checks

6. Which camera?  All cameras have spatial measurement potential! AAG, Seattle- April 2011  Digital SLR!  Fixed or variable zoom lens?  Never purchase “top of the range”

7. Camera calibration  Necessary for accurate spatial data acquisition! AAG, Seattle- April 2011  Difficulties!  What software?  Matlab, PhotoModeler, IWitness, etc. camera focal length (f) principal point offset(x P, y P ) radial lens distortion (K 1, K 2, K 3 ) tangential distortion (P 1, P 2 )

8. Fieldwork/control AAG, Seattle- April 2011 Photo acquisition: Infinity focus/f8 Infinity focus/f8 Fastest shutter speed possible/tripod Fastest shutter speed possible/tripod Obtain redundant imagery Obtain redundant imagery Control  Don’t skimp!  Well distributed  Withhold 20% and use as “checkpoints”- RMSE or mean error and standard deviation? Visit site prior Visit site prior capture images “in pairs/triplets” capture images “in pairs/triplets”

9. RMSE or mean error + standard deviation? AAG, Seattle- April 2011 Provide measures of: Bias- true reflection of systematic error Bias- true reflection of systematic error Variation- true reflection of “random error” Variation- true reflection of “random error” Conventional measure: Better measure?:

10. Benefits of convergent imagery!  Former Ph.D. Student- Dr Rene Wackrow AAG, Seattle- April 2011  Test object- planar test field with added blocks  Automated DEM extraction- compare elevations with planar “truth”

11. Normal imageryconvergent imagery! AAG, Seattle- April 2011  Test object- planar test field with added blocks  Automated DEM extraction- compare elevations with planar “truth”

12. DEM of differences- Nikon D80 (10MP) AAG, Seattle- April 2011 Normal case Mean error: 0.4 mm Standard deviation: +/-0.4mm Convergent case Mean error: 0.1 mm Standard deviation: +/- 0.2mm

13. Zhouqu- China 8 th Aug. 2010 AAG, Seattle- April 2011  “Tips” document, freely available- more later! Zhou Qu debris flow: Zhouqu mudslides death toll rose to 337 people, 1148 people missing

14. Measurement potential of imagery! AAG, Seattle- April 2011

15. Measurement potential of imagery! AAG, Seattle- April 2011  Video fly-thru!  Gradient of debris slope!

16. Conclusion  Prime purpose, raise awareness of the activities of ISPRS Working Group V6: http://isprsv6.lboro.ac.uk/ http://isprsv6.lboro.ac.uk/  Special Issue of the Photogrammetric Record: http://onlinelibrary.wiley.com/doi/10.1111/j.1477-9730.2010.00590.x/full http://onlinelibrary.wiley.com/doi/10.1111/j.1477-9730.2010.00590.x/full  “Tips” document, providing simple guidance.  Also some recent work/interests:  Potential of convergent image geometry  Potential of digital imagery using consumer grade digital cameras AAG, Seattle- April 2011 16 of 15