Examples Of The Use Of Photogrammetry In Forensic Engineering And Accident Reconstruction
One Definition Of Photogrammetry Is, The Use Of Photographs For Making Maps. For Our Purposes, Photogrammetry Means The Extraction Of Dimensions In One Plane From Oblique View Photographs. Although There Is Software To Analyze In Three Dimensions, This Discussion Is Limited To A Single Surface Or Plane. The Software Chosen For Illustration Is Trans4 By J. Rolly Kenny2, Which Employs The Four-Point Transformation Method. To Start An Analysis A Print Is Attached To A Digitizer Pad. Then, With The Software Primed And Waiting On A Signal, A Mouse Button Is Clicked When The Cross-Hairs Of The Mouse Are Placed Over A Point On The Print. The Digitizer Will Send A Stream Of Data Back To The Computer, And The Software Will Read And Store The Location Of The Pad Under The Print At The Point. When All Points Of Interest Have Been Located In Pad Coordinates, The Real Or Measured Coordinates Of Four Of The Points Are Entered By Hand. The Software Then Computes The Real Coordinates For All Of The Points. The Four Points Of Reference Are Called Base Points (Bp). No Three Of Them Can Be In A Line, And All Points Of Interest Must Lie On The Same Plane.