Borut Zalik

• PhD
• Principal Investigator at University of Maribor

Maximizing the energy output of photovoltaic (PV) systems is becoming increasingly important. Consequently, numerous approaches have been developed over the past few years that utilize remote sensing data to predict or map solar potential. However, they primarily address hypothetical scenarios, and few focus on improving existing installations. Thi...

Computer resources and programming solutions have always been utilised with the aim of improving efficiency; consequently, many optimisations have been developed in the past. This chapter first considers some typical characteristic optimisations in computing. Following this, a string transformation technique, Move with Interleaving (MwI), is explai...

After a boom that coincided with the advent of the internet, digital cameras, digital video and audio storage and playback devices, the research on data compression has rested on its laurels for a quarter of a century. Domain-dependent lossy algorithms of the time, such as JPEG, AVC, MP3 and others, achieved remarkable compression ratios and encodi...

Data compression algorithms tend to reduce information entropy, which is crucial, especially in the case of images, as they are data intensive. In this regard, lossless image data compression is especially challenging. Many popular lossless compression methods incorporate predictions and various types of pixel transformations, in order to reduce th...

This paper introduces a new method for the region segmentation of images. The approach is based on the raster-scan paradigm and builds the segments incrementally. The pixels are processed in the raster-scan order, while the construction of the segments is based on a distance metric in regard to the already segmented pixels in the neighbourhood. The...

Large binary images are used in many modern applications of image processing. For instance, they serve as inputs or target masks for training machine learning (ML) models in computer vision and image segmentation. Storing large binary images in limited memory and loading them repeatedly on demand, which is common in ML, calls for efficient image en...

Feature selection is predominantly used in machine learning tasks, such as classification, regression, and clustering. It selects a subset of features (relevant attributes of data points) from a larger set that contributes as optimally as possible to the informativeness of the model. There are exponentially many subsets of a given set, and thus, th...

Feature selection is predominantly used in machine learning tasks, such as classification and regression. It selects a subset of features (relevant attributes of data points) from a larger set that contributes as optimally as possible to the informativeness of the model. There are exponentially many subsets of a given set, and thus, the exhaustive...

A new algorithm is presented for detecting the local weak reflection symmetries in raster images. It uses contours extracted from the segmented image. A convex hull is constructed on the contours, and so-called anchor points are placed on it. The bundles of symmetry line candidates are placed in these points. Each line splits the plane into two ope...

Various implementations of the Move with Interleaving transform are discussed in this paper, with the transformation itself explained briefly at first. The transform has an expected time complexity of O(n), where n represents the length of the sequence being transformed. The importance of implementation also grows as the sequences become longer. Th...

In the past years various methods have been developed to estimate high-resolution solar potential in urban areas, by simulating solar irradiance over surface models that originate from remote sensing data. In general, this requires discretisation of solar irradiance models that estimate direct, reflective, and diffuse irradiances. The latter is mos...

A new compact encoding is presented of rasterized bi-level shapes at multiple resolutions. The encoder accepts the Freeman chain code in four directions (F4) at the input, and builds a multi-resolution code named MrCC. The encoding process constructs the coarser representation of F4 chain code, and the resulting MrCC codes simultaneously. MrCC enco...

This paper proposes a new string transformation technique called Move with Interleaving (MwI). Four possible ways of rearranging 2D raster images into 1D sequences of values are applied, including scan-line, left-right, strip-based, and Hilbert arrangements. Experiments on 32 benchmark greyscale raster images of various resolutions demonstrated tha...

The paper presents a new algorithm for reflection symmetry detection, which is specialized to detect maximal symmetric patterns in an Earth observation (EO) dataset. First, we stress the particularities that make symmetry detection in EO data different from detection in other geometric sets. The EO data acquisition cannot provide exact pairs of sym...

Multispectral satellite imagery offers a new perspective for spatial modelling, change detection and land cover classification. The increased demand for accurate classification of geographically diverse regions led to advances in object-based methods. A novel spatiotemporal method is presented for object-based land cover classification of satellite...

Učbenik Aplikacije računalniški algoritmov je namenjen študentom prve stopnje študijskega programa računalništvo in informacijske tehnologije s ciljem, spoznati algoritme, ki jih uporabniki pri svojem delu pogosto uporabljajo. Z implementacijo teh algoritmov bodo študentje pri prepotrebno rutino za za vstop v umetnost programiranja univerzalnega st...

The characterisation of geometric shapes produces their concise description and is, therefore, important for subsequent analyses, for example in Computer Vision, Machine Learning, or shape matching. A new method for extracting characterisation vectors of 2D geometric shapes is proposed in this paper. The shape of interest, embedded into a raster sp...

This paper demonstrates the capabilities of three-dimensional (3D) LiDAR scanners in supporting a safe distance maintenance functionality in human–robot collaborative applications. The use of such sensors is severely under-utilised in collaborative work with heavy-duty robots. However, even with a relatively modest proprietary 3D sensor prototype,...

A new approach is proposed for lossless raster image compression employing interpolative coding. A new multifunction prediction scheme is presented first. Then, interpolative coding, which has not been applied frequently for image compression, is explained briefly. Its simplification is introduced in regard to the original approach. It is determine...

Automatic building reconstruction from laser-scanned data remains a challenging research topic due to buildings' roof complexity and sparse data. A novel automatic building reconstruction methodology, based on half-spaces and a height jump analysis, is presented in this paper. The proposed methodology is performed in three stages. During the prepro...

Datasets often lack diversity to train robust classification models, capable of being used in real-life scenarios. Neural network-based generative models learn characteristics to generate synthetic (i.e. augmented) data, with the goal of increasing the diversity in datasets. A comparison is presented between Beta-VAE and WGAN-GP as ResNet-18 based...

Datasets often lack diversity to train robust classification models, capable of being used in real-life scenarios. Neural network-based generative models learn characteristics to generate synthetic (i.e. augmented) data, with the goal of increasing the diversity in datasets. A comparison is presented between Beta-VAE and WGAN-GP as ResNet-18 based...

Acts of fraud have become much more prevalent in the financial industry with the rise of technology and the continued economic growth in modern society. Fraudsters are evolving their approaches continuously to exploit the vulnerabilities of the current prevention measures in place, many of whom are targeting the financial sector. To overcome and in...

This paper introduces a novel approach to increase the spatiotemporal resolution of an arbitrary environmental variable. This is achieved by utilizing machine learning algorithms to construct a satellite-like image at any given time moment, based on the measurements from IoT sensors. The target variables are calculated by an ensemble of regression...

Reliable forest growth forecasting requires detailed tree data for forest simulation, while manual on-site collection of relevant data is work-intensive and unfeasible in larger forests. This paper proposes a complete methodology for fully automated forest growth simulation that relies primarily on airborne topographic Light Detection And Ranging (...

A new algorithm is presented for detecting the global reflection symmetry of geometric objects. The algorithm works for 2D and 3D objects which may be open or closed and may or may not contain holes. The algorithm accepts a point cloud obtained by sampling the object’s surface at the input. The points are inserted into a uniform grid and so-called...

LiDAR is a remote sensing technology that enables measuring distances using laser beams. Over the last two decades, LiDAR has established itself primarily in the field of Earth observation and has subsequently taken advantage of its capabilities in stationary and mobile platforms, providing real-time solutions for e.g. autonomous driving, robotics,...

V članku predstavimo postopke obdelave velikih količin nestrukturiranih geometrijskih podatkov, pridobljenih s prebirniki LiDAR. Najprej opišemo postopke klasifikacije točk LiDAR v točke, ki ležijo na Zemljinem površju. Opravimo kratek pregled obstoječih metod nato pa na kratko predstavimo našo metodo, temelječo na konceptih matematične morfologije...

This work introduces a new region merging algorithm operating in raster space represented by a 4-connected graph. Necessary definitions are introduced first to derive a new merging function formally. An implementation is described after that, which consists of two steps: a determination of the shared trails of the input cycles, and construction of...

Trees are natural objects, where deviations through the branches amplify geometric data for 3D representation and bring challenges to various applications dealing with 3D models, such as compression, visualization, symmetry detection, and radiative transfer simulation. This data article describes dataset of approximately symmetric 3D tree models wi...

This paper introduces a new integrated framework for short-term time series forecasting used as decision logic support in Energy Management Systems (EMS). The proposed framework defines data preprocessing, forecast model training, and adaptation techniques. For data preprocessing, Gaussian and Kalman filtering were used in offline learning on histo...

This paper aims to automatically reconstruct 3D building models on a large scale using a new approach on the basis of half-spaces, while making no assumptions about the building layout and keeping the number of input parameters to a minimum. The proposed algorithm is performed in two stages. First, the airborne LiDAR data and buildings’ outlines ar...

Satellite air pollution data sources are presented in this article. Satellite missions are listed and described, and corresponding instruments measuring the concentration of greenhouse gases or other parameters that affect air pollution. Main data hubs are enumerated, and other platforms providing access to the data in different formats. Some platf...

A new method for encoding a sequence of integers, named Binary Adaptive Sequential Coding with Return to Bias, is proposed in this paper. It extends the compressing pipeline for chain codes’ compression consisting of Burrows Wheeler Transform, Move-To-Front Transform, and Adaptive Arithmetic Coding. We also explain when to include the Zero-Run Tran...

Increasing population and urbanisation threaten sustainable urban development due to increased resource consumption and emissions. As buildings are one of the largest energy consumers, it is crucial that their thermal load can be inspected on a large scale and at the highest resolution possible. The proposed method is performed in two stages. First...

Tree pruning is a labor and cost-intensive task. Still, it is a necessary activity that ensures a high yield of good quality products in horticulture and increases the overall health of trees in general. Extensive research has been done attempting to automate this labor-intensive procedure, lower the cost, and demand a skilled workforce. We introdu...

Navidezno in obogateno resničnost lahko uporabimo tudi na področju predstavitev novih izdelkov in idej širši javnosti. Z njima lahko uporabnike in potencialne kupce seznanimo z izdelkom že v času njegovega razvoja. V članku opisujemo naše izkušnje s predstavitvijo rezultatov projekta MAHEPA. Gre za evropski projekt v okviru programa Obzorje 2020, z...

We present a framework for multi-objective optimization of fruit tree pruning within a simulated environment, where pruning is performed on a virtual tree model, and its effects on tree growth are observed. The proposed framework uses quantitative measures to express the short-term and long-term effects of pruning, for which potentially conflicting...

Burrows-Wheeler Transform, followed by Move-To-Front Transform, are often used transformation techniques in data compression. They may reduce the information entropy of the input sequence, which becomes more compressible in this way. This paper suggests an alternative, a Prediction-based Move-To-Front Transform, which may replace the aforementioned...

The availability of high-resolution LiDAR (Light Detection And Ranging) geospatial data has increased immensely, providing new opportunities to solve challenges in the field of spatial energy planning. This paper presents a new method for large-scale placement of photovoltaic arrays over buildings' rooftops in an optimal manner by using the global...

This paper introduces a new lossy approach for compression of cartoon images. The image is firstly partitioned into regions of roughly the same colour. The chain codes are then determined of all regions. The sequence of the obtained chain code symbols is transformed with the Burrows-Wheeler Transform, Move-To-Front transform, and compressed with Ru...

This paper introduces improvements to the algorithm that was proposed in 2001 by Chen and Chen. The algorithm constructs a quadtree directly from Freeman chain code in four directions. We have improved the algorithm in two ways: Firstly, a time efficient solution using the space filling Z-order curve is proposed for a self-intersection case that wa...

Network model recently has become a popular tool for studying complex systems. Detecting meaningful natural groups of nodes called communities in complex networks is an important task in network modeling and analysis. In this paper, the automatic network community detection is formulated as an optimization problem facilitated by node attraction. Th...

Most 3D point cloud watermarking techniques apply Principal Component Analysis (PCA) to protect the watermark against affine transformation attacks. Unfortunately, they fail in the case of cropping and random point removal attacks. In this work, an alternative approach is proposed that solves these issues efficiently. A point cloud registration tec...

A lossless chain code compression algorithm consisting of Burrows-Wheeler Transform, Move-To-Front Transform, and a modified interpolative coding is presented in this paper. The interpolative coding divides a strictly increasing array of integers and encodes the middle element recursively, where the required number of bits is obtained from the diff...

In the paper, we present a method for space-efficient representation of geometric tree models, which are provided as skeletons with radii attached to individual branch segments. The proposed approach uses a new differential 3D chain code to encode orientation changes of consecutive branch segments, which allows optimizing chain code generation for...

Realistic and interactive visualization of individual trees is a desirable functionality in numerous applications for landscape planning, ecosystem simulations, and forest management. However, achieving a persuasive visualization of extensive forests while maintaining an interactive experience remains a challenge. This paper introduces a new framew...

This paper describes the use of graph analysis for spatial networks. The use of community detection algorithms for detecting communities- groups of similar objects within networks of land cover objects to determine the land use is evaluated. Land cover to land use transformation requires some knowledge to merge land cover objects. Community detecti...

Mobile crowdsensing is a powerful paradigm that exploits the advanced sensing capabilities and ubiquity of smartphones in order to collect and analyze data on a scale that is impossible with fixed sensor networks. Mobile crowdsensing systems incorporate people and rely on their participation and willingness to contribute up-to-date and accurate inf...

Automatic network clustering is an important method for mining the meaningful communities of complex networks. Uncovered communities help to understand the potential system structure and functionality. Many algorithms that use multiple optimization criteria and optimize a population of solutions are difficult to apply to real systems because they s...

This paper presents a novel robust approach developed specially for watermarking airborne LiDAR data, which consist of a large cloud of geo-referenced points and has some unique characteristics. The approach consists of the following steps: (1) Defining the marker circular areas, in which the watermark bit will be embedded; (2) Dividing the marker...

Competition between individual trees is a major factor influencing the development of forests. However, due to the complexity of such interactions, that span over vast geographic areas, systematic analysis of competition has only recently become possible through the concepts of so-called predictive analytics. The rationale behind the utilised appro...

Nowadays, computers are an integral part of the education process in many fields and levels. Although numerous research has been done on Computer‐Based Education (CBE), there are still open questions that have to be answered. Authors have faced some of those important questions over the years while developing the teaching applications from various...

Land monitoring is performed increasingly using high and medium resolution optical satellites, such as the Sentinel-2. However, optical data is inevitably subjected to the variable operational conditions under which it was acquired. Overlapping of features caused by shadows, soft transitions between shadowed and non-shadowed regions, and temporal v...

This paper proposes a novel visualization and analytics tool, which is capable of searching for hidden relationships and patterns within large multi-dimensional data. The goal of the presented tool is to represent the data in novel ways, understandable and useful to the data owner, with new visual and statistical analytics. Various statistics are o...

This paper considers the use of interpolative coding for lossless chain code compression. The most popular chain codes are used, including Freeman chain code in eight (F8) and four directions (F4), Vertex Chain Code (VCC), and three-orthogonal chain code (3OT). The whole compression pipeline consists of the Burrows–Wheeler transform, Move-To-Front...

Community detection is a key to understanding the structure of complex networks. Many community detection approaches have been proposed based on the modularity optimization. Algorithms that optimize one initial solution often get into local optima, but algorithms that simultaneously optimize a population of solutions have high computational complex...

With the growing urbanization and environmental concerns over buildings' energy consumption and carbon footprint, the demand for energy-efficient building design is greater than ever. This paper addresses these concerns by presenting a novel method for estimating and optimising the thermal load (i.e. total energy load for heating and cooling) of a...

Cutaneous Melanoma (CM) is a malignant tumour, and is one of the most rapidly growing cancers. Discovering a melanoma in the early stages of the disease is extremely difficult and, as such, only an invasive disease stage can be identified easily with the naked eye. Dermatoscopy is a diagnostic method intended to maximise early detection of CM perfo...

3D reconstruction of trees is an important task for tree analysis but the most affordable approach to capture real objects is with a camera. Although, there already exist methods for 3D reconstruction of trees from multiple photographs, they mostly handle only self-standing trees captured at narrow angles. In fact, dense feature detection and match...

This paper introduces a new algorithm for Boolean operations on rasterized geometric shapes that are represented with chain codes. The algorithm works in three steps. Firstly, the chain code symbols are transformed in the Hilbert space, where the overlaid chain code symbols are recognised. After that, a suitable starting cell is determined. Finally...

The increasing availability of airborne Light Detection And Ranging (LiDAR) data provides new opportunities for environmental simulations. This paper proposes a new method for wind resource assessment by using wind simulation over 3D geometry extracted from classified LiDAR data. The simulation of wind flow is performed by using Smoothed Particle H...

Community detection in large networks has been a focus of recent research in many of fields, including biology, physics, social sciences, and computer science. Most community detection methods partition the entire network into communities, groups of nodes that have many connections within communities and few connections between them and do not iden...

This paper deals with a method for determining the rating of roofs’ segments in urban areas regarding their suitability for the installation of different photovoltaic (PV) systems. In order to determine the received irradiance of individual roofs, their geometry is described based on LiDAR (Light Detection And Ranging) data, in order to estimate ac...

Quantitative analysis of the vascular network anatomy is critical for the understanding of the vasculature structure and function. In this study, we have combined microcomputed tomography (microCT) and computational analysis to provide quantitative three-dimensional geometrical and topological characterization of the normal kidney vasculature, and...

Vasculature segmentation and reconstruction workflow. The flowchart shows the sequential order in which individual subroutines are arranged in our computational protocol in order to segment out the vascular structure and to reconstruct it. Used abbreviation are SO for the Strahler order, SOp for the parent vessel Strahler order, SOd for the daughte...

Global scale parameter analysis. (PDF)

Complex network theory offers an efficient mathematical framework for modelling natural phenomena. However, these studies focus mainly on the topological characteristics of networks, while the actual reasons behind the networks’ formation remain overlooked. This paper proposes a new approach to complex network analysis. By searching for the optimal...

This paper proposes a parallelized online optimization of low voltage distribution network (LVDN) operation. It is performed on a Graphics Processing Unit (GPU) by combining the optimization procedure with the load flow method. In the case study, performed for the test LVDN with distributed generators (DGs) and controllable loads, differential evol...

The paper proposes a new method to detect changes in point clouds of the Earth surface acquired by the LiDAR technology. The shape-analysis methods based on mathematical morphology are used. To extract objects, differences are determined from two input datasets, each acquired at different times and serving as the basis for detection of changed obje...

By combining stereo images in order to generate accurate point-clouds of the Earth's surface, the UAV (Unmanned Aerial Vehicle) has recently become a cheap alternative to the well-established LiDAR systems. In this paper, we verify to which extent the methods that were developed to process aerial LiDAR data can be used when presented by the limitat...

Within the last few years, the increase of the world's energy consumption has substantially impacted the environment. Solar energy initiative is more than ever involved to tackle this issue, especially when deploying PV (photovoltaic) systems over large-scale residential areas. However, not all surfaces in these areas are economically suitable, whi...

Kljub obstoju različnih tujih računalniških programov, ki omogočajo fotogrametrični zajem podatkov iz aerofotografij velikega formata, tudi slovenska stroka zadnjih dvajset let ne zaostaja za tujino in izdeluje svoje fotogrametrične programe. Ti omogočajo večjo optimizacijo 3D-zajema pri slovenskih projektih: na primer pohitritev zajema zaradi vnap...

This paper proposes a new method for the detection of vegetation in LiDAR data. As vegetation points are characterised by non-linear distributions, they are efficiently recognised based-on large errors obtained when applying the local fitting of planar surfaces. In addition, three contextual filters are introduced capable of dealing with those exce...

This paper considers the suitability of string transformation techniques for lossless chain codes' compression. The more popular chain codes are compressed including the Freeman chain code in four and eight directions, the vertex chain code, the three orthogonal chain code, and the normalised directional chain code. A testing environment consisting...

Proliferation of distributed generation units, integrated within the distribution network requires increased attention to their proper placements. In urban areas, buildings' rooftops are expected to have greater involvement in the deployment of PV (photovoltaic) systems. This paper proposes a novel procedure for determining roof surfaces suitable f...

This paper presents a novel method for testing the inclusion status between the points and boundary representations of polyhedra. The method is executed entirely on the GPU and is characterized by memory efficiency, fast execution and high integrability. It is a variant of the widely known ray-crossing method. However, in our case, the intersection...

Aerial laser scanning of the whole territory of Slovenia was performed with first return point densities of 2-5 points/m 2 in years 2014 and 2015. The data were processed with Slovenian gLidar software, enabling quick product line and resulting in the following products: classified point cloud, ground point cloud, digital terrain model (DTM) with g...

Beta cells in the pancreatic islets of Langerhans are precise biological sensors for glucose and play a central role in balancing the organism between catabolic and anabolic needs. A hallmark of the beta cell response to glucose are oscillatory changes of membrane potential that are tightly coupled with oscillatory changes in intracellular calcium...