ISSUE 53 Expert Witness Journal - Journal - Page 28
Above, demonstration of Optical Flow Tracking between two consecutive frames.
Pose Estimation / Camera Calibration
Just like tracking, our brains are also very good at processing depth information and perceiving 3D scenes
effortlessly. The CV equivalent technique of this is
called Pose Estimation. Pose Estimation involves calculating camera positions in 3D space or deriving 3D
information of objects from camera sensors placed at
a fixed position. This is a common application used in
the field of Photogrammetry where we try to ascertain
information about physical objects derived from noncontact sensor systems like cameras and laser scans.
Optical Character Recognition
Optical Character Recognition (OCR) is the process
of extracting printed texts into digital readable formats. This involves applying image processing techniques to remove any noise and artefacts and then the
texts are identified by comparing each pixel’s relative
contrast to the background. Machine Learning Models are used to identify geometric features such as dots,
lines, and strokes along with their relative location. It
then uses probabilistic methods to determine the most
likely character given the detected features. More
advanced processes have the capability to check for
spelling mistakes when identifying words or correct
grammar mistakes if whole sentences are being
How Hawkins Can Help?
Video recordings and images are often the most
powerful forms of evidence in an investigation. Our
experts are fluent in the process of applying CV methods to a variety of our service offerings which include,
but are not limited to, investigations of personal injuries, road traffic collisions and structural failures. We
can perform a more robust and holistic analysis of images and video recordings more quickly and efficiently
using established CV techniques. The use of CV enables us to remove human frailties and subjectivity
from the interpretation of visual media, allowing us to
analyse data objectively, and leverage our skills as
scientists and mathematicians.
About the Author
Inigo graduated from the University of Warwick
obtaining a First-Class Masters Degree in Mathematics. Inigo studied topics including Machine Learning,
Advanced Real Analysis and Group Theory. His dissertation project explored the mathematics behind
Linear Inverse Theory with applications in medical
tomography. This included programming in MATLAB to demonstrate the inner workings of a CTscan using Randomised Algebraic Reconstruction
Techniques.
Inigo is an Associate in our Reigate office and uses his
skills to expand and strengthen Hawkins’ offerings in
Digital Forensic Services. Inigo has developed and
implemented a new 3D Photogrammetric Modelling
and Forensic Photogrammetry Service whereby he
performs 3D modelling of retained forensic exhibits
such as pipes, buildings, fire damaged electrical
appliances and vehicles.
3D Point cloud data are very useful when trying to estimate the camera
pose. Here we used point cloud data to approximate where the left image
was taken relative to the scene and in turn, approximated the slant angle
of the tree
EXPERT WITNESS JOURNAL
recognised, increasing the accuracy of its results (but
to be used with caution). The benefit of using OCR is
that it can handle a variety of image data such as
scanned documents, photographs, screenshots, or
digital camera images; it performs independently of
the existence of metadata.
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