Calibration of the Nikon D200 for Close-Range Photogrammetry Lassana Sheriff Office of Science, Science Undergraduate Laboratory Internship Program City College of New York, New York NY SLAC National Accelerator Laboratory, Menlo Park, California August 13, 2009

Outline (AEG) and Metrology Department Camera (Nikon D200) Software and Targets Camera Model Central Perspective Projection Brown Extension Model 2D Calibration Wall 3D Calibration Structure Results Conclusion and Future August 13, 2009 Lassana Sheriff SULI 2009 2

Alignment Engineering Group (AEG) and Metrology Department Measuring and Aligning objects with survey instruments (Laser Tracker) For instance: Magnets and other components in LCLS from the electron gun to the dump The project is to evaluate the possibility to use photogrametry as another survey technique Photogrametry: Photographic Metrology August 13, 2009 Lassana Sheriff SULI 2009 3

Camera Nikon D200 and built-in flash. DX format 23.7mm x 15.7mm 10.2 megapixels(6 micron square pixels) Nikkor 20mm lens August 13, 2009 Lassana Sheriff SULI 2009 4

Software and Targets Australis Coded Targets (Retro-reflective) 60 degree lose reflective property. Scale Bar (Distance between the targets on the bar is known) can use to scale measurement August 13, 2009 Lassana Sheriff SULI 2009 5

Reflective Targets Coded Spherical targets Rotatable targets August 13, 2009 Lassana Sheriff SULI 2009 6

Object co-ordinate system Image point m x Y p r yp o xp X c i Projection plane Z C i Perspective center Z Y M Object point X O Object co-ordinate system August 13, 2009 Lassana Sheriff SULI 2009 7

Camera Parameters Interior Orientation of the Camera Focal length and the principal points of the camera: c, xp, and yp Extended by Brown Model k1,k2,k3 (radial distortion) p1, p2 (decentering) b1, b2 (shearing) Compare, analyze and assess the camera’s stability August 13, 2009 Lassana Sheriff SULI 2009 8 8

Interior Orientation August 13, 2009 Lassana Sheriff SULI 2009 9

Central Perspective Projection This equation illustrates an ideal basic photogrammetry model August 13, 2009 Lassana Sheriff SULI 2009 10

2D wall One partial wall in AEG Laboratory Coded Targets 13 points measured with a laser tracker Different Angles August 13, 2009 Lassana Sheriff SULI 2009 11

Flat Wall without Processing No Australis August 13, 2009 Lassana Sheriff SULI 2009 12

Australis window for the wall August 13, 2009 Lassana Sheriff SULI 2009 13

3D 3D Structure Coded Targets Reflective Sphere Same Angles as 2D Started late August 13, 2009 Lassana Sheriff SULI 2009 14

3D without Processing No Australis August 13, 2009 Lassana Sheriff SULI 2009 15

Graphs Line Graphs (trends) Histogram (distribution) 41 data sets 2D wall 6/29-8/7 23 data sets 3D structure 7/15-8/7 August 13, 2009 Lassana Sheriff SULI 2009 16

Line Graph c August 13, 2009 Lassana Sheriff SULI 2009 17

Line Graph xp August 13, 2009 Lassana Sheriff SULI 2009 18

Line Graph yp August 13, 2009 Lassana Sheriff SULI 2009 19

Histogram c August 13, 2009 Lassana Sheriff SULI 2009 20

Histogram xp August 13, 2009 Lassana Sheriff SULI 2009 21

Histogram yp August 13, 2009 Lassana Sheriff SULI 2009 22

Results Line Graphs and their purpose (No trend as data is scattered and good stability within the day) Example: Focal length, some points are far off the trend likely due to transportation and handling purposes Histogram (distribution of the parameters) Normal Distribution (xp and yp) alike and are not normally distributed Focal length more like a normal distribution. August 13, 2009 Lassana Sheriff SULI 2009 23

Conclusion and Future Camera can be used for Photogrammetry measurements but calibrate before each use. Mechanical improvement to the camera 3D structure from more angles to get true 360 degree. August 13, 2009 Lassana Sheriff SULI 2009 24

Acknowledgement The Science Undergraduate Laboratory Internship SULI program wouldn't have been possible without the funding of the Department of Energy DOE here at Stanford Linear Accelerator Center SLAC. Special acknowledgment goes to my mentor BRIAN FUSS for his diligent guidance and support. I would like to acknowledge CATHERINE LECOCQ for her resilient work and direction in the entire project. And finally acknowledgement to BRENDAN DIX for his participation in building the 3D structure; and to the rest of the members of Alignment Engineering Group for their support. …and thanks to Stephen and all the students!! August 13, 2009 Lassana Sheriff SULI 2009 25