International Journal of Environment and Geoinformatics

228-238

Authors: Quy Giang PHAM

In recent years, as a result of urbanization and the development of tourism and services, land market in Vietnam has been blooming. This has made land management in general and financial management of land in particular become more important than ever. Based on GIS technology, the present study has built a database with full details of each land parcel in order to support financial management of land in Quat Lam, a coastal tourist town in Nam Dinh Province. The database also provides land users and managers with sufficient information on transportation, hydrology and service systems, which influence land price. The database allows land managers to carry out financial management related tasks such as: Searching for land parcel information; calculation of registration fees, calculation of income tax from the transfer of land use rights, compensation for ground clearance upon land acquisition; search of land parcels according to financial capability; development of specialized thematic maps regarding land prices, financial obligations and legal status of land, etc. The established database is practically valuable for land managers as well as land users as it facilitates the process of change updates, data analysis, processing and sharing, and consequently improving the efficiency in financial management of land.

252-264

Authors: Levent BAT, Quratulan AHMED, Ayşah ÖZTEKİN, Elif ARICI

Heavy metals can remain in the marine ecosystems for a long time, they may affect biota in the food chain as a result. Sometimes the existence of xenobiotics causes so great a alter in the ecosystem that a return to earlier, natural conditions is not viable. Human pressure on the sea’s resources is increasing, it affects the health of many organisms, leading to changes in the food chains and influencing accumulation in the tissues of biota. Sea cucumbers are being used for heavy metal pollution studies. They are preferred with their many features such as easy collection from the land, feeding with organic matter, contact with sediment, maintenance in laboratories, obtaining sufficient tissue, consuming some species. This review covers heavy metal studies with sea cucumbers in different seas. The results are compared with each other. In addition, the evaluation of the consumed sea cucumber species in terms of human health has been discussed.

272-279

Authors: Ozan OZTURK , Batuhan SARITÜRK, Dursun Zafer SEKER

Segmentation is one of the most popular classification techniques which still have semantic labels. In this context, the segmentation of different objects such as cars, airplanes, ships, and buildings that are independent of background and objects such as land use and vegetation classes, which are difficult to discriminate from the background is considered. However, in image segmentation studies, various difficulties such as shadow, image blockage, a disorder of background, lighting, shading that cause fundamental modifications in the appearance of features are often encountered. With the development of technology, obtaining high spatial resolution satellite imageries and aerial photographs contain detailed texture information have been facilitated easily. Parallel to these improvements, deep learning architectures have widely been used to solved several computer vision tasks with an increasing level of difficulty. Thus, the regional characteristics, artificial and natural objects, can be perceived and interpreted precisely. In this study, two different subset data that were produced from a great open-source labeled image sets were used to segmentation of roads. The used labeled data set consists of 150 satellite images of size 1500 x 1500 pixels at a 1.2 m resolution, which was not efficient for training. In order to avoid any problem, the imageries were divided into smaller dimensions. Selected images from the data set divided into small patches of 256 x 256 pixels and 512 x 512 pixels to train the system, and comparisons between them were carried out. To train the system using these datasets, two different artificial neural network architectures U-Net and Fully Convolutional Networks (FCN), which are used for object segmentation on high-resolution images, were selected. When the test data with the same size as the training data set were analyzed, approximately 97% extraction accuracy was obtained from high-resolution imageries trained by FCN in 512 x 512 dimensions.

289-299

Authors: Başak SAVUN-HEKİMOĞLU

Due to their unique properties, azo dyes are extensively used, especially in the textile industry. Due to their low biodegradability, these compounds cannot be treated in wastewater treatment plants and discharges of these effluents poses a serious threat to the receiving water bodies. In the literature, several advanced oxidation processes have been studied for decolorization and mineralization of these toxic compounds. Among these advanced oxidation processes, the UV/H2O2 process has attracted great attention with its high efficiency in removing these compounds. The goal of this paper is to review the kinetic rate expressions developed to describe azo dye degradation by UV/H2O2 process. A detailed review of pseudo-first-order reaction mechanism, as well as reactor design models, is provided. Finally, a set of experiments are conducted with Reactive Black 5 to compare the model estimations with the observed data. In addition, a regression model is developed using response surface methodology to optimize operating conditions. The experimental results indicate that the optimum pH value that gives the maximum reaction constant is 5.74. Moreover, initial dye concentration is found to be a more significant parameter for decay rate constant than pH value. The open questions and future research topics are also discussed.

305-318

Authors: Abraham COİMAN

This study was conducted to estimate the land use and land cover (LULC) changes from 1986 to 2016 at Zamora municipality in Venezuela. Landsat 5 TM, Landsat 7 ETM+, and Landsat 8 (OLI/TIRS) images were obtained to evaluate the shoreline dynamics of the Valencia lake and the magnitude of LULC changes. The images were processed and classified through the object-oriented approach in eCognition Developer 8, for collecting ground-truth data was used Google Earth Engine Python API and Excel software for accuracy assessment. ArcGIS 10.4 and QGIS 2.18 were employed for spatial analysis. It was found that scrublands and farmlands experienced important reductions in area, 13029 ha, and 818 ha respectively, whereas forest, built-up, and water bodies classes showed remarkable increments in area, 11792 ha, 1482 ha, and 634 ha correspondingly. The Valencia lake shoreline underwent an upward trend wherein more than 50% of its raising occurred during the last two study years (2003-2016). It was also observed that land use and land cover changes prompted conflicts with other land uses, 337 ha of lands with high potential for crop yields were affected by the lake shoreline increment and built-up areas grow at a rate of 81 ha /yr. for the last two study years (2003-2016) mainly on lands with high potential for agricultural use.

325-334

Authors: Metin AYDOĞDU , Hakan YILDIZ , Ediz ÜNAL , Seda KÜLEN

Plant health and plant density can be monitored through indices values calculated from reflectance charateristics of plants. This study aims to investigate the effects of different rates of nitrogen fertilizer on spectral reflectance characteristics of dryland winter wheat and to determine and select the most reliable vegetation indices for Nitrogen (N) status assesment (N contents of leaves) of winter wheat canopy in early, late and whole development stages. The field experiment was carried out in randomized block design with three replications and 0, 40, 80, 120, 160 kg/ha N doses applied between 2012-2013 years in İkizce Farm experiment field. In each plot, spectroradiometer readings were taken during growing period from planting to harvest various plant vegetation indices (NDVI, RDVI, SAVI, MTVI, MCARI-1, MCARI-2, TCARI, TVI, SIPI, NPCI, Red Edge (750-700), Red Edge (740-720)) were calculated from measured spectroradiometric values. A total of 90 different indices were calculated to obtain the relationship between nitrogen accumulation and hyperspectral indices (structural, chlorophyll pigment, red edge indices). The simple linear determination coefficients (R²) between those indices and leaf nitrogen contents in different development stages of early, late, and whole season were calculated. During the early period of tillering to bolting, (Feekes 4-7) NDI-1, NDI-2, SR-7, Red Edge indices (708-850 nm.) have the highest determination coefficients (R²) of 0.643, 0.641, 0.620 with RMSE values of 5.996, 6.039, 6.129 and relative percentage error values (%RE) of 23.07, 23.23, 23.58 % respectively. During the period of heading to ripening (Feekes 8-10), PhRI, NDV-3, NDVI-4 visible (Green Zone), red, red edge and near infrared (NIR) indices (531-800 nm.) showed the highest determination coefficients of 0.734, 0.708, 0.699 with RMS values of 3.089, 3.205, 3.149 and relative percentage error values of 40.37, 41.89, 41.16 % respectively. Considering all growing period in 2013 of tillering to ripening, ( Feekes 4-10); SR-14, SRPI, TVI visible area (blue + green) and Red Edge indices (415-750 nm.) have determination coefficients of 0.742, 0.699, 0.646 and RMS values 1.203, 0.902, 0.697 and relative percentage error values of 7.15, 5.36, 4.14 %, respectively. High determination coefficient (R²) between plant nitrogen uptake and reflectance charecteristics were attained as HVI (r= 0.806 p<0.0.1 **), OSAVI (r= 0.794, p<0.0.1**), NDVI (r= 0.794, p<0.0.1**) and HNDVI (r= 0.793, p<0.0.1**).

347-355

Authors: Canan KOCABALDIR, Mehmet Ali YÜCEL

Energy demand is gradually increasing due to rapid population growth. Using fossil fuels for energy production destroys the environment and fossil energy-based reserves are expected to be depleted in the future. Renewable energy sources are needed to minimize environmental impacts. Solar energy is among the most researched and invested renewable energy sources. There is diversity in renewable energy sources in Çanakkale province but it is not sufficient when the potential is considered. Other renewable power plants except the wind should also be increased among the newly planned plants. Carrying out a comprehensive solar power plant analysis is the first step to provide a cost-effective and well-performing project, and so choosing a suitable location is a critical point towards developing solar energy projects. Knowing potential sites is a fundamental point for annual power plant production forecasting and financial feasibility. With the integration of Geographic Information Systems (GIS) and Multi-Criteria Decision Analysis (MCDA); a more reliable analysis is carried out, the most suitable places can be determined by considering various criteria. Within this study, using spatial analysis, it is aimed to determine areas where photovoltaic (PV) solar power plant can be established in Çanakkale province by GIS-MCDA and how much of energy demand can be supplied in case of installation. Criteria and restriction factors to be used were determined by scanning the literature in detail as part of the relevant legal regulations. According to the restriction map generated, 96% of Çanakkale province is restricted site since the restriction factors was considered refinedly. Analytical hierarchy process (AHP) will be used as a method of analysis and after acquiring the optimal sites, the annual electric power generation potential in those sites will be calculated. The outputs of this study will contribute development strategy and national energy planning.

365-371

Authors: Oktay ÇETİN, Mesut KÖSEOĞLU

Maritime transportation security can be violated by piracy and terrorist attacks along with a wide variety of threats which may interrupt the free flow of goods through sea lanes of communication. Any disruption of this flow due to threats which may be encountered in international and territorial waters can adversely affect global economy. This paper aims to review the security challenges faced by maritime industry involving risks emanating through marine environment, threats to sustainable maritime economics, mutual international efforts to preserve stability, security in maritime areas of interest to maintain the flow of commodities throughout the World and conventional maritime security risks as well as the potential economic benefits of the Arctic Region occurring from increasingly diminishing of the sea ice. Considering recent developments in the Arctic and the new security concerns, emerging security strategies in the Arctic Region with a view to its effects on Maritime Economics is emphasized.

114-119

Authors: Aydın TOKUŞLU

The International Maritime Organization (IMO) has adopted a new regulation to prevent air pollution from ship emissions which concentrated on reducing green gas emissions from shipping for existing ships, and energy efficiency measures for the new ship. This new regulation imposes a measure which is called Energy Efficiency Design Index (EEDI). This measure aims to reduce CO2 emissions and global environmental pollution by using fewer fossil fuels and less greenhouse gas emissions. EEDI is an implementation for all new ships larger than 400 GT. In this paper, one of the container ships in the Turkish maritime trade fleet was investigated and its emissions were estimated. The Energy Efficiency Design Index (EEDI) of the ship was calculated. Some useful proposals have been presented to reduce the harmful effects of CO2 exhaust gas emission.

127-131

Authors: Abdullah AKSU , Ömer Suat TAŞKIN , Mehmet Emre ÇETİNTASOGLU , Nagihan ERSOY KORKMAZ ERSOY, Cihan TORLAK , Nuray ÇAĞLAR BALKIS

Synthesize of low price stationary phases with permanent groups for reversed-phase liquid chromatography (RP-HPLC) has gained great importance in the past several years. In chromatographic analyses, silica gels are commonly used as a supporting material as they give high mechanical strength and swelling resistance. Additionally, different particle and pore size availability and low cost makes these materials one of the most suitable stationary phase. In this work, chemically bonded C8 phase was synthesized by sol-gel route and instead of toxic silicone alkoxides, non-toxic water glass was chosen as a precursor. Linking process of C8 groups to silica gel was carried out by trimethoxy(octyl)silane. The end-capping and C8 binding procedure was analyzed by Fourier transform infrared (FTIR) spectroscopy and morphology of C8 particles were characterized by scanning electron microscope (SEM).

140-146

Authors: Kamil KARATAŞ , Nurgül Seher ALTINIŞIK

In Turkey, cadastral studies to determine the position, areas, and legal status of the real estate parcels have been carried out for a period of approximately 100 years by various laws, measurement methods, measurement instruments, and substrates. In Turkey, it is necessary to update 40% of the existing parcels because of problems such as produced cadastral substrates that do not reflect the ground structure, inadequate standards for technical reasons, and insufficient spatial data for the establishment of systems. The technical part of the studies for the cadastral update is carried out by the use of modern measurement methods and advanced technological devices, with the contribution of the private sector by the tender procedure. The unmanned aerial vehicle (UAV), which is one of the technological devices, can provide three-dimensional appearance and accuracy, the ability to interpret the land, and time reduction in the studies for cadastral updates. In this study, the contribution of data obtained by a UAV to the detailed studies was investigated for 56 parcels on a cadastral island that has an area of 24.71 ha for the renewal of cadastral parcels related to Karaköy Village of Çorum Province, Osmancık District. The number of detail points determined by the classical method was 392, while the number of detail points determined by the UAV was 682.

157-164

Authors: Nagihan ERSOY KORKMAZ , Nuray ÇAĞLAR , Abdullah AKSU , Tuba ÜNSAL

In this study, the presence, distribution and concentration of steroidal hormones (Estrone, 17β-estradiol and 17α-ethynylestradiol) were examined in the Golden Horn Estuary (Marmara Sea, Turkey) for one year. The bottom and surface water samples were collected from nine stations in the Golden Horn Estuary four seasons a year. In order to determine the hormone amounts, solid phase extraction was applied to the water samples and then these samples were analyzed on the HPLC with DAD detector. Recoveries of these hormones were range from 92–100% for estuary water. The highest concentrations of estrone, 17β- estradiol, 17α- ethynylestradiol were measured as 1.069 µg/L, 5.25 µg/L, 1.65 µg/L in Golden Horn, respectively. The concentrations of these three hormones are found higher in bottom water than the surface water and the highest concentrations of all hormones were determined in winter season.

172-183

Authors: Filmon Tquabo GEBREMARİAM , Solomon HABTU , Yemane ADANE , Tesfa-alem GEBREEGZİABHER , Negasi SOLOMON , Eyasu YAZEW

Consistent and well-timed information regarding the extent of irrigated areas is very important for the development of the agricultural sector. This study investigated the reliability of traditional estimates of irrigated area coverages from three micro-dam irrigation schemes. High resolution Google Earth (GE) and medium resolution satellite imagery coupled with an intensive ground survey were employed to determine irrigation area coverages. Landsat-8 image pre-processing and classification was carried out in ENVI 5.0 software. In comparison to the Landsat-8 based estimates, the traditional method over-estimated 87% of the total 14 cases considered. The level of discrepancies in scheme area coverages range from a minimum of -20% (underestimated) to a maximum of 224%. Besides this, the traditional estimates were ranging from -1.8 to 238% of GE-based estimates. Whereas, the Landsat-8 based estimates slightly overestimated it by 1.8% -16% of GE-based estimates. On the other hand, the traditional estimates tend to underestimate/ignore crops with smaller area coverages and overestimate crops with relatively larger area coverages. The results hinted that the using medium and low resolution satellite imagery could improve the data collection and reporting from irrigated agriculture in developing countries.

191-204

Authors: Sena AHMETOĞLU , Ayşegül TANIK

Carbon footprint involves the calculation of direct and/or indirect emissions of fossil fuels that emit greenhouse gases (GHG) that lead to greenhouse effect responsible of global warming. The resulting carbon dioxide (CO2) due to the activities of the individuals/institutions emerges into the atmosphere with the consumption of energy. The amount of emissions throughout the world in general and in Turkey, and the main reasons of these emissions is explained in this study. Carbon footprint management and tracking since 1990’s in Turkey are underlined, and carbon tax and carbon trade terminologies are introduced. Scope classification for determining emissions according to three classification of ISO 14064 Greenhouse Gas Calculation and Validation Management System is described. Scope-1 covers the activities that create direct carbon footprint. In this context, the fossil fuels used by the projects for heating or energy needs and the emissions from the fuels of the vehicles are taken into consideration. Within Scope-2, the carbon footprints of the emissions caused by the electrical energy consumed by the projects are considered. Scope-3 is an indirect carbon footprint and includes emissions from projects that are not directly emission-driven projects. With this study, it is aimed to address the carbon footprint caused by the entire construction sector that extends from the production of construction materials to the construction and post-construction (operation) stages. This sector is focused on due to its significance regarding GHG emissions globally. Emissions from non-owned or uncontrolled sources such as production, transportation, leased assets, outsourced services and disposal of the wastes generated during the construction or operation of the stages of different building typologies are included in the carbon footprint calculations.

213-220

Authors: Adalet DERVİSOGLU , Burhan Baha BİLGİLİOĞLU , Nur YAĞMUR

Tuz Lake and its surrounding lakes (Tersakan Lake, Duden Lake, Bolluk Lake, Esmekaya Lake, Kopek Lake, Akgol) are placed in the Central Anatolia region. These lakes maintain the ecosystem integrity and make a good habitat for numerous bird species, especially flamingos. The Duden Lake is located within the boundaries of the Tuz Lake Special Environmental Protection Area and was declared as a protected area in 1992. The surface and underground water around Kulu District of Konya feed the Duden Lake, which is tectonically formed through the Kulu Stream. The lake with the average area of 860 hectares is unfortunately in risk of extinction. Remote sensing has been the most useful tool to obtain spatial and temporal information about wetlands and it provides up-to-date, accurate, and cost-effective information. Remote sensing methods and applications are used quite effectively on wetlands. The traditional pixel-based classification method is applied to different satellite images in wetlands over many decades, and the usage of object-based classification method has started recently comparing to the pixel-based one. This study aimed to determine the coastline of the wetlands. Sentinel 2 satellite images, which provide free access and high spatial resolution, are used to observe the coastline of Duden Lake through the usage of pixel-based and object-based classification methods in all the seasons. The applicability of the methods in determination of shallow wetland coastline is studied and evaluated. The results of the pixel-based and the object-based classification images are compared by accuracy assessment.

6-22

Authors: Engin MERİÇ, Niyazi AVSAR, M. Baki YOKEŞ, İpek F. BARUT, Feyza DİNÇER, Cüneyt BİRCAN, Erol KAM

Benthic foraminifer assemblages of the Turkish Aegean coasts have been investigated. Sediment samples from Alibe and Maden Islands (Balıkesir), Kusadası (Aydın), Cesme Ilıca Bay (Izmir) and northwestern coast of Karaburun Peninsula (Izmir) have been analysed. Similarities, as well as dissimilarities were observed between the assemblages from different locations. The Red Sea orginated alien foraminifer Amphistegina lobifera Larsen was found to form a very dense population around the south and west part of a submarine spring water in Kusadası, where as it was replaced by Ammonia compacta Cushman and Elphidium crispum (Linné) assemblages on the northern and eastern parts. Euthymonacha polita (Chapman) has been first recorded in Kusadası and it is also abundant in the Ilıca Bay. The Red Sea originated Coscinospira acicularis (Batsch) has also been first recorded in the Mediterranean from Ilıca Bay. Presence of the individuals with colored tests indicates the presence of heavy metals in spring waters. Aberrant aperture morphologies observed in some of the Vertebralina striata d’Orbigny individuals attracts attention. Abundance of individuals with colored tests, morphological deformities or togetherness, as well as the Red Sea originated species indicates the special environmental and ecological conditions around the submarine springs.

33-44

Authors: Chokri BEDOUI

The study of water erosion has always been a major concern for human societies. Efforts to reduce resulting forms of degradation and to understand their extent have not ceased. This article aims to identify vulnerable and water-erosion-prone areas in the study area. This is achieved through a predictive and descriptive approach leading to the integration of main physical parameters from various sources with direct observation data. The use of remote sensing, GIS and direct observation according to PAP/RAC guidelines has made it possible to prioritize areas at risk of erosion. The basin's lands show a general predisposition to water erosion, with 80% of them experiencing significant, high or very high erosion, including 20% for the last two categories. This situation is linked to a high erodibility of the geological outcrops of the basin (81%), with a low to very low degree of soil protection through vegetation cover (80% of the surface). The descriptive phase shows eroded surfaces of about 18%, a proliferation of ravines (12% of the surfaces) of which 6% are hierarchical ravines and bad lands. The integration phase, while confirming most of the previous data, provides an overview of the trend towards the extension of gullies observed during the descriptive phase to neighboring lands that were not initially subject to erosion. This study shows that a good integration of descriptive and predictive methods can lead to a good understanding of water erosion, which will facilitate solutions to control this phenomenon. It also shows the importance of GIS, remote sensing and their integration with direct field observation in order to produce a document that can be used, at a low cost, as a decision support tool.

54-63

Authors: Demissie Tsega MALLIE, Kefelegn Getahun CHERNET, Tesfaye Debela DUGUMA

This study was aimed at assessing afro-alpine and sub-afro-alpine biodiversity habitat loss and fragmentation of Gugu Mountain Ranges using geospatial techniques. Satellite imageries, key informants and field observation were the major sources of data. The land sat images of 1989, 2001 and 2019 were used to compute change and fragmentation level. ERDAS IMAGINE 2014, ArcGIS 10.4 and FRAGSTAT version 4.2 was used to process data. Image differencing (extent and rate of change), normalized difference vegetation index (NDVI), and area, shape, and aggregation metrics were used to analyze the data. The findings showed that a decline in greenness value and shrinking of afro-alpine and sub-afro-alpine habitat by 1.49% between 1989 and 2001, and 2.62% between 2001 and 2019. Due to this, the total area covered declined from 3540.65 to 1846.98 hectares over the last 30 years. Moreover, the result further revealed that not only decline in size but also there were habitat fragmentations in the study area.

68-79

Authors: Olanrewaju LAWAL

Creation and differentiation of regions are some of the basic tasks in geographic analysis. Regionalisation attempts to create a generalised representation of the processes which is taking place at the level of the amalgamated geographic units. To this end, this study examined the combined use of demographic, economic and poverty characteristics of States across Nigeria to create regions relevant for economic and development planning. The study utilised dependency ratios derived from gridded age structure data, Gross domestic product (GDP), poverty index. K-Means and Max-p algorithm were used for identification of regions. Correlation analysis showed that Youth dependency and total dependency have a strong statistically significant positive relationship (r=0.998, p<0.01) indicating that dependency in the country is driven by youth. The best K-Mean clustering implementation without considering contiguity identified 12 regions with a ratio of between and total sum of squares (RBTSS) of 0.789. The Max-p algorithm was tested with population constrain, the best result identified 9 regions with RBTSS of 0.611 constrained by a minimum population of 8% and implemented with the greedy local search algorithm, this was the same for the simulated annealing approach (SA). With high dissimilarity still common across a handful of the regions identified, a further test was carried out using a minimum bound of 3 States and the SA local search approach. The best result identified 11 contiguous regions with only one region having a relatively high within region dissimilarity and a RBTSS of 0.626. The results confirmed that there are more than 6 regions as currently defined for the country. The analyses showcased an example of knowledge discovery from a spatial dataset which could support regional development planning. From the results, there is a clear need for re-examination of current regions and designing of better-defined regions to ensure that development is guided by evidence.

88-92

Authors: Berkay BAHADUR, Metin NOHUTÇU

Traditionally, ground control points (GCPs) are utilized to determine absolute image orientations indirectly in aerial triangulation. For a long time, differential and relative GNSS (Global Navigation Satellite System) positioning techniques have been extensively used to establish GCPs. In our country, the establishment and measurement of GCPs are instructed in the related regulation based on differential GNSS techniques. One of the two methods described in the related regulation is based on establishing, at least, C3 level networks with maximum base length of 10 km and with minimum 35-minute observation time. In an alternative method, without base length restriction, GCP coordinates can be determined being connected to at least 3 TUSAGA-Active stations and with minimum 120-minute static observation. The expected precision for the coordinates of GCPs are described to be better than 5 cm in horizontal and 6 cm in vertical within the regulation. Although differential techniques can provide highly accurate positioning solutions, they are required at least two receivers to mitigate GNSS error sources. Additionally, positioning accuracy obtained from these techniques are strictly dependent on the distance from reference stations. It is clear that all these raise the operational cost and system complexity of differential GNSS techniques. In recent years, Precise Point Positioning (PPP), which enables centimeter- or millimeter-level positioning accuracy with only one receiver on a global scale, has emerged as an alternative positioning method. Over the last decade, PPP has attracted considerable attention within the GNSS community due to its exceptional benefits such as operational simplicity, cost-effectiveness, elimination of base station requirement. However, the main drawback of PPP is relatively long observation period required to achieve a specific positioning accuracy, for example, nearly 50 min to reach 10 cm or better horizontal accuracy with 30 seconds sampling rate. On the other hand, the completion of GLONASS constellation and the emergence of new satellite systems, such as Galileo and BeiDou, offers considerable opportunities to improve the PPP performance. The combinations of different GNSS constellations, namely multi-GNSS, strength the number and geometry of visible satellites, and therefore, reduces the convergence time significantly. Additionally, the new generation GNSS receivers make possible to collect more observations (even up to 100Hz), which provides abundant data for PPP processing. Taking all these into account, the principal objective of this study is to investigate the usability of PPP in establishing GCPs for aerial triangulation. For this purpose, an experimental test was conducted to evaluate the positioning performance of multi-GNSS PPP with high-frequency GNSS receivers (1 Hz). The results indicate that 5 cm or better horizontal and vertical positioning accuracy can be achieved by multi-GNSS PPP process within approximately 30 minutes using highfrequency GNSS receivers. Considering these results and its operational simplicity, it can be said that PPP is a robust alternative for the establishment of GCPs.

102-107

Authors: Baran GULMEZ, Fatih DEMIRTAS, Irem YILDIRIM, Uğur, M. LELOĞLU, Mustafa YAMAN, Eylem T. GUNEYI

Features are distinctive landmarks of an image. There are various feature detection and description algorithms. Many computer vision algorithms require matching of features from two images. Large number of correct matches with homogeneous distribution in the images is needed for robustness of the image matching. The matches are generally obtained using a feature distance threshold and ambiguous matches are rejected using a ratio test. This paper proposes a method that can be added to image matching pipeline for enhancing homogeneous distribution and increasing the number of matched feature points. After successfully matching an image pair, spatially close feature points go through an elimination process which aims to decrease ambiguity at the second matching step. Then, a coarse geometric transformation between two images is calculated, through which the detected feature points in one image (i.e. the moving image) are projected to the other image (i.e. the fixed image). Then, feature points from the moving image are matched to neighboring feature points of the fixed image within a pre-determined spatial distance. This narrows down the possible candidates and enables less correct matches being rejected because of the ratio test. The effectiveness and feasibility of our method is demonstrated with experiments on images acquired from a drone camera during flight.