Volkan Yilmaz

Karadeniz Technical University · Department of Geomatics Engineering

Forest environment and topographic obstacles tend to reduce the positioning performance of precise point positioning (PPP) with ambiguity resolution (AR) and may even prevent radio signals from reaching the global navigation satellite systems (GNSS) antenna. In this study, we investigated the positioning performance of PPP-AR in a forest environmen...

The objective of this research is to assess the effects of climate change on Türkiye by utilizing data catalogues provided by the Google Earth Engine (GEE) cloud-computing platform. The utilized data catalogues encompassed precipitation, Land Surface Temperature (LST), EvapoTranspiration (ET), Potential EvapoTranspiration (PET), Normalized Differen...

This study develops a novel approach for identifying buildings that were damaged in the aftermath of the Kahramanmaraş earthquakes on February 6, 2023, which were among the most devastating in the history of Türkiye. The approach involves using two pre-event and one post-event Sentinel-1 and Sentinel-2 images to detect changes in the varying-sized...

Digital Terrain Models (DTMs), which represent the topography of the bare Earth surface, are widely used in many geomatics applications. In parallel to the emergence of sophisticated Unmanned Aerial Systems (UASs) in recent years, they are produced from point clouds generated through aerial images taken from digital imaging systems mounted on UASs....

The coarse spatial resolutions of hyperspectral (HS) satellite images limit their use in many applications. The spatial structure quality of HS images can be improved by fusing them either with higher-resolution panchromatic (PAN) images, or with higher-resolution multispectral (MS) images. Fusion of HS images can be done with fusion methods that a...

Pansharpening fuses the spatial features of a high-resolution panchromatic (PAN) image with the spectral features of a lower-resolution multispectral (MS) image to generate a spatially enriched MS image. Numerous pansharpening strategies have been developed for more than three decades, which forces the analysts who intend to apply pansharpening to...

Pansharpening is an efficient way of producing images of higher spectral and spatial fidelity. Since pansharpening aims to generate a spectrally enhanced image with the same spatial detail content of the source panchromatic (PAN) image, the source multispectral (MS) image is upsampled to the size of the source PAN image prior to pansharpening. Seve...

Image classification applications require images of high colour quality. However, it is not always possible to obtain such images due to the technical constraints in the sensors and cost problems. Hence, this study, for the first time in the literature, used the multi-objective metaheuristic optimization algorithm Non-Dominated Sorting Genetic Algo...

The majority of the ground filtering techniques proposed so far use several user‐defined parameter values. Since no standard protocols exist to define these parameters, obtaining the optimum filtering performance is very hard, especially in large‐extent areas with abrupt topography changes. This, of course, reveals the necessity of some more effici...

The ground filtering is essential for the extraction of the topography of the bare Earth surface. Various ground filtering methods have been developed, especially in the last three decades. The main disadvantage of the ground filtering methods is that their performances are highly dependent on some user-defined parameter values. Hence, the analysts...

Pansharpening, which aims at producing complementary images that contain the spectral and spatial characteristics of different images, is an essential task for many remote sensing applications. To date, a huge amount of pansharpening techniques have been introduced for such a purpose. Considering the previous work on this topic, it can be concluded...

Pansharpening aims to fuse a lower-resolution multispectral (MS) image and a higher-resolution panchromatic image, resulting in an image with the color quality of the former and spatial detail quality of the latter. Of all, the component substitution (CS)-based pansharpening methods have drawn attentions with their ability to produce sharp images....

Image fusion aims to spatially enhance a low-resolution multispectral (MS) image by utilizing a high-resolution panchromatic (Pan) band. Various image fusion methodologies have been proposed with the aim to improve the spatial detail quality without deteriorating the colour content of the input MS image. Previous studies revealed the fact that ther...

Bileşen değişimi tabanlı görüntü kaynaştırma yöntemleri literatürde en fazla kullanılan görüntü kaynaştırma yöntemleri arasındadır. Bu yöntemler konumsal detayları iyileştirmedeki başarılarına rağmen girdi çok bantlı görüntülerin renk yapısını bozma eğilimindedirler. Bu durumun temel nedeni bu yöntemlerin girdi çok bantlı görüntülerin bantlarından...

This paper investigates the behaviour of the double-curvature Deriner dam, which is in the operation phase and also one of the highest dams in the world. In order to determine the displacements, a geodetic network consisting of twelve reference and seven object points was measured in four periods by means of the Global Navigation Satellite Systems...

This study proposed a metaheuristic pansharpening (MP) method, which performs in a Synthetic Variable Ratio (SVR)-like manner. The proposed method introduced the Symbiotic Organisms Search (SOS) algorithm, an advanced nature-based optimization algorithm, to estimate a weight for each multispectral (MS) band to achieve the optimum intensity. The SVR...

There is no such thing as ‘the best image fusion method’ in terms of both spectral and spatial fidelity. This fact encourages the researchers to develop more advanced approaches in order to optimally transfer the spatial details without distorting the colour content. Component substitution (CS)-based image fusion methods have been proven to produce...

Uzaktan algılanmış görüntülerden elde edilen doku bilgisi yardımıyla yüksek doğruluklu arazi örtüsü haritalarının üretilmesi mümkündür. Kaynaştırılmış bir görüntüdeki doku bilgisinin sınıflandırma işlemine entegre edilmesinin sınıflandırma işleminin doğruluğuna olumlu yönde katkı yapması muhtemeldir. Bu çalışmada Brovey, Multiplicative (MCV), PCA (...

This study proposed to improve the performance of the conventional Synthetic Variable Ratio (SVR) image fusion algorithm by means of the Genetic Algorithm (GA). The proposed Genetic Algorithm-Based Synthetic Variable Ratio (GA-SVR) method utilizes the GA to estimate the optimum band weights used to generate the intensity component. Performance of t...

Field measurements are the main source of information when determining stand parameters, which are essential to produce an effective forest management plan. However, conducting terrestrial measurements is neither time- nor cost-efficient in most cases. In recent years, the advent of sophisticated remote sensing technologies has enabled the extracti...

Pansharpening, which is transferring the spatial content of a high-resolution panchromatic (PAN) band into a lower-resolution multispectral (MS) image to produce a spatially enhanced MS image, has always been one of the hottest topics of image processing. Numerous studies have focused on developing approaches to inject the spatial details with mini...

Hyperspectral images offer a good separability among land cover classes, owing to their advantages to provide spectral bands with narrow wavelength intervals. It is also possible to further increase classification accuracy of hyperspectral images by integrating some auxiliary data to classification process. The aim of this study was to increase the...

In recent years, the advent of unmanned aerial vehicles (UAV)-based photogrammetry has enabled the collection of accurate and comprehensive information from the surface of the Earth. Owing to low-altitude flights, it is possible to generate high-density point clouds, which are useful for accurate representation of topography of the land surface. Gr...

Owing to their numerous benefits to humanity and other species, forests are considered the lungs of our planet. Unplanned use of forests causes the humanity face with a wide variety of critical issues such as climate destabilisation, air pollution, temperature instability, landslides, etc. This, of course, attaches importance to the sustainability...

Dams are among the most significant energy sources in today's world. Hence, it is vital to maintain their sustainability. Geodetic and non-geodetic techniques are used to investigate the deformations of the dams periodically and to prevent any possible dam accidents, loss of life and property. This study aims at investigating the horizontal movemen...

In recent years, remote sensing technologies have been used to collect forest inventory, owing to their ability to provide comprehensive and accurate information about the physical characteristics of forests. Tree crown diameter, which can be defined as the maximum width of the projection of a tree crown, is one of the most significant stand parame...

Tree crown diameter, which is the diameter of the circle enclosing the projection of tree crown, is one of the most important stand parameters that should be identified before the production of forest management plans. This feature is generally obtained with terrestrial measurements, which may not be time- and costefficient in most cases. The use o...

Advancing technology enables the extraction of accurate spatial information relating to the features on the ground. Owing to low-altitude flights, stereo aerial photos taken from digital cameras mounted on unmanned aerial vehicles (UAV) make it possible to generate point clouds as dense as LiDAR (Light Detection and Ranging) point clouds. Contrary...

Digital Terrain Model (DTM) generation is one of the leading applications in photogrammetry. A DTM is generated by the interpolation of ground points retrieved by ground filtering, which is the removal of the points belong to above-ground objects from point cloud. In the literature, a wide variety of ground filtering approaches have been reported f...

Recently, photovoltaic systems have been developed and production of electricity directly from the sunlight has gained importance and become widespread. Photovoltaic systems will obviously be more important in the near future with their low cost, compared to other energy production methods. For example, in some European countries, municipalities pr...

Digital Terrain Models (DTMs) as well as Digital Surface Models (DSMs) have been widely used in many forestry applications, especially in locating forest roads, developing transportation planning, and determining the stand parameters. Generally, LiDAR (Light Detection and Ranging) point clouds have been used to generate DTMs, since LiDAR technology...

With the advent of unmanned aerial vehicles (UAVs) for mapping applications, it is possible to generate 3D dense point clouds using stereo images. This technology, however, has some disadvantages when compared to LiDAR (Light Detection and Ranging) system. Unlike LiDAR, digital cameras mounted on UAVs are incapable of viewing beneath the canopy, wh...

In Turkey, forest management plans are produced by terrestrial surveying techniques for 10 or 20 year periods, which can be considered quite long to maintain the sustainability of forests. For a successful forest management plan, it is necessary to collect accurate information about the stand parameters and store them in dynamic and robust database...

Digital Elevation Model (DEM) generation is one of the leading application areas in geomatics. Since a DEM represents the bare earth surface, the very first step of generating a DEM is to separate the ground and non-ground points, which is called ground filtering. Once the point cloud is filtered, the ground points are interpolated to generate the...

Digital Terrain Models (DTM) have been widely used in many forestry applications, especially in determining the stand parameters. Generally, LiDAR (Light Detection and Ranging) point clouds have been used to generate DTMs, since LiDAR technology is able to provide multiple returns, which is very useful to separate the ground surface and non-ground...

Recently, forest resources are planned in the sense of based multiple use forest planning, in which the actual status of forests are needed to be identified accurately to present the products and services offered by forests, except for the wood products. In this regard, precise estimation of stand types and stand parameters affects the accuracy and...

This study aims to increase the accuracy of the object based classification approach to differentiate the spectrally similar land cover types to create thematic maps depicting the current land use status in rangeland. Firstly, the multispectral and panchromatic bands of a WorldView-2 MS and Pan images are fused. The fused WV-2 image is then classif...

Image fusion is the production of high-resolution images by combining the spatial details of a high-resolution image with the spectral features of a low-resolution one. Reports of various quality metrics to evaluate the spectral and spatial qualities of fused images have been published. However, metrics may lead to misinterpretation due to inherent...

Image fusion is the combination of spectral characteristics of a low-resolution image and spatial features of a higher resolution image to produce the spatially enhanced image. Different fusion techniques have been introduced in the literature. Fusion algorithms tend to yield good results when using single sensor images as input data sets. Fusion p...

Solar energy is environmentally safe, efficient and sustainable energy source. Recently, photovoltaic systems have been developed and production of electricity directly from the sunlight has gained importance and become widespread. Photovoltaic systems will obviously be more important in the near future with their low cost compared to other energy...

Ülkemizde kesin meşcere haritaları üretilirken envanter çalışmalarında ağaç türü karışımı, kapalılık, çap, yaş ve boy gibi çeşitli meşcere parametreleri yersel ölçümlerle toplanmaktadır. Meşcerelerdeki türlerin çap dağılımlarının belirlenebilmesi için, ağaç tepe çapı ile gövde çapı arasında istatistiksel bir ilişkiden yararlanılabilmektedir. Ağaç t...

Transferring spatial details of a high-resolution image into a low-resolution one is called image fusion. There are some different fusion methods introduced. Due to the nature of fusion process, these methods may damage the spectral quality of the low-resolution multispectral image to a certain extent. In the literature, there are some metrics that...

İnsansız hava araçlarına (İHA) monte edilen kameralar yardımıyla yeryüzünün görüntülenmesi yersel ölçüm tekniklerine göre bazı avantajları beraberinde getirmektedir. İnsansız hava araçlarının kullanılması ile az maliyetle kısa sürede çok yüksek konumsal ve zamansal çözünürlüklü görüntüler elde edilebilmektedir. Elde edilen bu yüksek konumsal çözünü...

Görüntü kaynaştırma konumsal çözünürlüğü yüksek olan bir görüntüdeki konumsal detayların konumsal çözünürlüğü düşük olan görüntülere transfer edilmesidir. Farklı görüntü kaynaştırma yöntemleri farklı kalitede kaynaşmış görüntüler sunmaktadır. Bazı görüntü kaynaştırma yöntemleri yüksek konumsal çözünürlüklü görüntüdeki detayları daha düşük konumsal...

Görüntü kaynaştırma konumsal çözünürlüğü yüksek olan bir görüntüdeki konumsal detayların konumsal çözünürlüğü düşük olan görüntülere transfer edilmesidir. Farklı görüntü kaynaştırma yöntemleri farklı kalitede kaynaşmış görüntüler sunmaktadır. Bu yöntemlerden bazıları düşük konumsal çözünürlüklü görüntünün spektral yapısını bozabilmektedir. Literatü...