St. philip’s college TAPE D ebriefing Focus Group January 16, 2013
The Smartphone D-tape
description
Transcript of The Smartphone D-tape
The Smartphone D-tape
A Lightening Talk presented by:Dr. John A. Kershaw, Jr.Professor of Forest MensurationFaculty of Forestry & EM, University of New Brunswick
1813
1913
1963
2013
There are some alternatives
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
Criteria• Fast• Accurate• Repeatable• Cheap• Automated
Smartphone• Decent high resolution camera• App development easy and cheaply distributed• Compact, and since most everyone has one, not an additional piece of
equipment
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
Epipolar Geometry
Two photos
The “Fundamental” Matrix
Coincident Photos
Add the DBH line, map the pixels from one photo to the other
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)