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The Smartphone D-tape

The Smartphone D-tape. A Lightening Talk presented by: Dr. John A. Kershaw, Jr. Professor of Forest Mensuration Faculty of Forestry & EM, University of New Brunswick. 1813. 1913. 1963. 2013. There are some alternatives. Close-range photogrammetric approaches.

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The Smartphone D-tape

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  1. The Smartphone D-tape A Lightening Talk presented by: Dr. John A. Kershaw, Jr. Professor of Forest Mensuration Faculty of Forestry & EM, University of New Brunswick

  2. 1813

  3. 1913

  4. 1963

  5. 2013

  6. There are some alternatives

  7. Close-range photogrammetric approaches • Stereo photographs with known center-point distances • Vanishing Point Horizon with laser pointer • Dual lasers with known laser distance • An alternative

  8. Criteria • Fast • Accurate • Repeatable • Cheap • Automated

  9. Smartphone • Decent high resolution camera • App development easy and cheaply distributed • Compact, and since most everyone has one, not an additional piece of equipment

  10. Goal • Take two photos, with random phone movement (distance, rotation and yawl) • From these two photos determine: • Camera shift • {X,Y,Z} coordinates • Estimate DBH

  11. Epipolar Geometry

  12. Two photos

  13. The “Fundamental” Matrix

  14. Coincident Photos Add the DBH line, map the pixels from one photo to the other

  15. DBH Estimate • OLS solution to the Fundamental Equation • Camera Focal Length and Camera Aspect Ratio used to convert from pixels to real world coordinates • DBH estimated from 3D coordinate distances • Include inclination angle for upper stem diameters (Grosenbaugh 1963)

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