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Sains Malaysiana 42(9)(2013): 1339–1344
Pendekatan
Pengesanan Titik Sauh Secara Automatik bagi Kesan Pin Peletup Senjata Api
(Automatic Anchor Point Detection Approach for Firearms Firing Pin
Impression)
Zun Liang Chuan1, Nor Azura Md Ghani2 1Pusat Pengajian Sains Matematik, Fakulti Sains dan Teknologi, Universiti
Kebangsaan Malaysia 43600 UKM Bangi, Selangor D.E, Malaysia
Universiti Teknologi MARA, 40450 Shah Alam, Selangor D.E,Malaysia
Received: 22 May 2012 / Accepted: 10 March 2013
ABSTRAK
Oleh sebab kejadian jenayah bersenjata api semakin berleluasa, pengecaman senjata api yang digunakan oleh penjenayah amat
diperlukan sebagai bahan bukti dalam mahkamah. Beberapa sistem pengecaman
senjata api telah diutarakan sebagai pengganti kepada
cara penyiasatan tradisional yang amat bergantung kepada kepakaran ahli
balistik. Pemetakan rantau tumpuan (ROI) berdasarkan kedudukan titik
sauh (PAP) sempadan bulatan kesan pin peletup pada tapak
kelongsong peluru merupakan langkah yang amat penting dalam sistem pengecaman
senjata api automatik. Walau
bagaimanapun, kaedah yang digunakan dalam kajian lepas bagi mengesan (PAP)
sempadan bulatan tersebut adalah sangat kompleks dan memerlukan masa
pemprosesan yang panjang. Kajian ini menerokai
algoritma yang efisien dan berkemampuan untuk mengesan PAP sempadan
bulatan secara automatik. Algoritma yang diutarakan
merupakan gabungan daripada penapis penajaman reruang, penormalan histogram,
pengambangan dan penganggar kuasa dua terkecil tak berpemberat. Dua kaedah pengambangan yang terkenal telah diuji dan dibandingkan,
iaitu kaedah pengambangan berasaskan pengelompokan dan kaedah berasaskan entropi. Di samping itu, penerokaan kesan saiz dan bentuk (ROI)
terhadap kadar pengelasan senjata api turut
dipersembahkan. Sebanyak 747 imej kesan pin peletup jenis sempadan bulatan
peletup yang dihasilkan oleh lima pucuk pistol yang
berlainan daripada jenis yang sama digunakan untuk menguji algoritma yang
diutarakan. Kadar pengelasan imej kesan pin peletup yang memberangsangkan (>
95%) telah dicapai dengan algoritma yang dicadangkan. Kajian juga mendapati
bahawa saiz dan bentuk pemetakan ROI mempunyai kesan langsung terhadap kadar pengelasan senjata api.
Kata kunci: Balistik forensik; rantau tumpuan; senjata api; titik sauh
ABSTRACT
Since the number of crimes involving firearms is becoming rampant,
identification of firearms used by criminals is a crucial step in the court.
Several automatic firearm identification systems have been developed to improve
on the traditional investigation method which relies heavily on the expertise
of the forensic ballistics experts. An important step in automatic firearm identification
is partitioning of the region of interest (ROI)
based on the position of the anchor point (PAP)
within the circular boundary of a firing pin impression. However, in the
previous studies, the methods used to determine the PAP of
a circular boundary are very complex and time consuming. This study explored
algorithms that are efficient and able to detect the anchor point of a circular
boundary automatically. The proposed algorithms are a combination of sharpening
spatial filter, histogram normalization, thresholding and an unweighted least
square estimator. Two popular threshold selection methods, namely
clustering-based and entropy-based threshold selection methods, have been
investigated and compared. In addition, exploration on the effects of size and
shape of ROI on the firearm classification accuracy rates were
discussed. A total of 747 images of circular boundary firing pin impression
produced by five different pistols of the same model were used to test the
proposed algorithms. Encouraging classification rates of the firing pin
impression images (> 95%) were achieved with the proposed algorithms. This
study also found that the size and the shape of the ROI partition
have a direct effect on the firearms classification rates.
Keywords: Anchor point; firearms; forensic
ballistics; region of interest
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*Corresponding author; email: lg@ukm.my
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