Indonesian Journal of Electrical Engineering and Computer Science Vol. 21, No. 2, February 2021, pp. 811~821 ISSN: 2502-4752, DOI: 10.11591/ijeecs.v21.i2.pp811-821  811 Journal homepage: http://ijeecs.iaescore.com Indonesian license plate recognition with improved horizontal-vertical edge projection Ida Nurhaida, Imam Nududdin, Desi Ramayanti Faculty of Computer Science, Universitas Mercu Buana, Indonesia Article Info ABSTRACT Article history: Received Feb 26, 2020 Revised Apr 7, 2020 Accepted May 6, 2020 License plate recognition (LPR) is one of the classical problems in the field of object recognition. Its application is very crucial in the automation of transportation system since it helps to recognise a vehicle identity, which information is stored in the license plate. LPR usually consists of three major phases: pre-processing, license plate localisation, optical character recognition (OCR). Despite being classical, its implementation faced with much more complicated problems in the real scenario. This paper proposed an improved LPR algorithm based on modified horizontal-vertical edge projection. The method uses for detecting and localising the region of interest. It is done using the horizontal and vertical projection of the image. Related works proved that the modified horizontal-vertical edge projection is the simplest method to be implemented, yet very effective against Indonesian license plate. However, its performance gets reduced when specular reflection occurs in the sample image. Therefore, morphological operations are utilised in the pre-processing phase to reduce such effects while preserving the needed information. Eighty sample images which captured using various camera configurations were used in this research. Based on the experimental results, our proposed algorithm shows an improvement compared with the previous study and successfully detect 71 license plates in 80 image samples which results in 88.75% accuracy. Keywords: Computer vision Image processing License plate recognition Morphology operation This is an open access article under the CC BY-SA license. Corresponding Author: Ida Nurhaida Faculty of Computer Science Universitas Mercu Buana Jl. Meruya Selatan no. 1, Indonesia Email: ida.nurhaida@mercubuana.ac.id 1. INTRODUCTION Object recognition is one of the most interesting fields among the computer vision researcher since it's applicable in many sectors of our everyday life. One of the classical problem that still relevant even today was license plate recognition, because of the many challenges that must be tackled such as variations of the license plate characteristics in each country around the world, noise in the image, environmental factors, etc. Many researchers around the world have developed many algorithms for license plate recognition. Still, due to the limited sample, most of them are crafted only for a specific country with specific license plate characteristics (background colour, format, font type, etc.). They might not work for other countries with different license plate characteristics. License plate in Indonesia has its unique characteristics. It has a black coloured background with a white border and text. The usage of unique alphabet code to differentiate license plates across the regions in Indonesia, also the license plate is structured based on a standardised format. The details are described within