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Recovery via SfM photogrammetry of latent footprint impressions in carpet.

Larsen, H.J., Budka, M. and Bennett, M. R., 2021. Recovery via SfM photogrammetry of latent footprint impressions in carpet. Journal of Forensic Sciences, 66 (4), 1495-1505.

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DOI: 10.1111/1556-4029.14718

Abstract

Impression evidence retained in carpet is usually recovered, if at all, in two dimensions via a vertical photograph. Here, we show that recovery is also possible via SfM photogrammetry and this gives good quality results that allow digital measurements both in the x-y plane and by depth (z-axis). This study focuses on recovery from polypropylene carpets which are widespread due to their resistance to wear and low cost. We show how traces can be recovered using both SfM photogrammetry and conventional photography with illumination provided via a crime scene light source. Experiments show that traces are retained for considerable time periods if left undisturbed, in excess of four weeks, but are quickly lost in under 8 hours by subsequent footfall. A simple simulation shows how the movement of an individual can be determined from carpet traces and the value of 3D recovery is illustrated via a set of experiments conducted with barefoot traces. We draw attention to the fact that 3D models allow a more statistical-based approach to be taken to match bare footprints at crime scenes. SfM photogrammetry is shown to provide a useful compliment to existing techniques and therefore worthy of further experimentation and potentially operational use.

Item Type:Article
ISSN:0022-1198
Additional Information:Research Funding UK Natural Environment Research Council. Grant Number: NE/M021459/1
Uncontrolled Keywords:barefoot impression ; carpet ; footwear impression ; photogrammetry ; structure from motion ; three-dimensional
Group:Faculty of Science & Technology
ID Code:35420
Deposited By: Symplectic RT2
Deposited On:21 Apr 2021 07:39
Last Modified:13 Apr 2022 01:08

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