Economics at your fingertips  

Ruler Detection for Autoscaling Forensic Images

Abhir Bhalerao and Gregory Reynolds
Additional contact information
Abhir Bhalerao: Department of Computer Science, University of Warwick, Warwick, Coventry, UK
Gregory Reynolds: Pattern Analytics Research Ltd, Solihull, UK

International Journal of Digital Crime and Forensics (IJDCF), 2014, vol. 6, issue 1, 9-27

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.

Date: 2014
References: Add references at CitEc
Citations: Track citations by RSS feed

Downloads: (external link) ... 018/ijdcf.2014010102 (application/pdf)

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link:

Access Statistics for this article

More articles in International Journal of Digital Crime and Forensics (IJDCF) from IGI Global
Bibliographic data for series maintained by Journal Editor ().

Page updated 2019-11-24
Handle: RePEc:igg:jdcf00:v:6:y:2014:i:1:p:9-27