Bhalerao, Abhir and Reynolds, Gregory (2014) Ruler detection for autoscaling forensic images. International Journal of Digital Crime and Forensics, Volume 6 (Number 1). pp. 9-27. doi:10.4018/ijdcf.2014010102

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Abstract

The assessment of forensic photographs often requires the calibration of the resolution of the image so that accurate measurements can be taken of crime-scene exhibits or latent marks. In the case of latent marks, such as fingerprints, image calibration to a given dots-per-inch is a necessary step for image segmentation, preprocessing, extraction of feature minutiae and subsequent fingerprint matching. To enable scaling, such photographs are taken with forensic rulers in the frame so that image pixel distances can be converted to standard measurement units (metric or imperial). In forensic bureaus, this is commonly achieved by manual selection of two or more points on the ruler within the image, and entering the units of the measure distance. The process can be laborious and inaccurate, especially when the ruler graduations are indistinct because of poor contrast, noise or insufficient resolution. Here the authors present a fully automated method for detecting and estimating the direction and graduation spacing of rulers in forensic photographs. The method detects the location of the ruler in the image and then uses spectral analysis to estimate the direction and wavelength of the ruler graduations. The authors detail the steps of the algorithm and demonstrate the accuracy of the estimation on both a calibrated set of test images and a wide collection of good and poor quality crime-scene images. The method is shown to be fast and accurate and has wider application in other imaging disciplines, such as radiography, archaeology and surveying.

Item Type:	Journal Article
Subjects:	H Social Sciences > HV Social pathology. Social and public welfare R Medicine > RA Public aspects of medicine T Technology > TA Engineering (General). Civil engineering (General) T Technology > TR Photography
Divisions:	Faculty of Science > Computer Science
Library of Congress Subject Headings (LCSH):	Forensic sciences, Criminal investigation, Image analysis , Rulers (Instruments), Legal photography, Scaling (Social sciences)
Journal or Publication Title:	International Journal of Digital Crime and Forensics
Publisher:	I G I Global
ISSN:	1941-6210
Official Date:	2014
Dates:	Date Event 2014 Published
Date of first compliant deposit:	3 March 2016
Volume:	Volume 6
Number:	Number 1
Page Range:	pp. 9-27
DOI:	10.4018/ijdcf.2014010102
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Embodied As:	1

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