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, Choong-Yeun Liong1* & Abdul Aziz Jemain1

1Pusat Pengajian Sains Matematik, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor D.E, Malaysia

 

2Pusat Pengajian Statistik dan Sains Pemutusan, Fakulti Sains Komputer dan Matematik

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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