Browsing by Author "Akturk E."

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Accuracy assesment of a low-cost UAV derived digital elevation model (DEM) in a highly broken and vegetated terrain
(2019-03-01) Akturk E.; Altunel A.O.
Digital Elevation Models (DEMs) are frequently used in geology, environment, engineering and architecture related studies. Along with the technological advances, there are also improvements in the production techniques of these data. The use of low cost UAVs and what they can achieve, are therefore important for researchers. This study was designed to find answers to two main questions. Firstly, in areas of challenging conditions, if it is feasible to produce DEM with the low-cost UAV imagery, and if the obtained precision would be comparable enough to those of the proven methods. Secondly, if the addition of Ground Control Points (GCPs) would further increase the precision. As a result of this research, the uncertainty, in other words the RMSE of the DEM data obtained from the area with challenging topography, was found to be 0.57 m. In addition, the use of GCPs provided 6 cm decrease in the overall error margin.
Examining the PALSAR-2 Global forest/non-forest maps through Turkish afforestation practices
(2020-08-17) Altunel A.O.; Akturk E.; Altunel T.
Forests and afforestation have significant importance, given the present course of World’s climate resulting from our insensitive behaviours, policies, ambitions, etc. Turkish Forest Service has departments, sole purposes of which are to combat desertification through afforestation, flood control, and watershed rehabilitation works. Majority of the works is carried out in the semi-arid central part of the country, which is known as the Irano-Turanian phytogeographic region. Hydroelectric dam projects, which have extensively been conducted to produce energy and to harness the rivers when needed, have been at the centre of these efforts in the region. Afforestation works, which have long been used to safeguard dam reservoirs, have always been associated with such projects because they are implemented even prior to water deposition. They along with the country’s managed forests are looked after as the natural forest cover. Improvements in remote sensing at this point enabled the agencies to diversify their efforts in monitoring the natural resources and strengthening the decision makers’ hand in management preferences in both global and regional scales. There are various data produced through the classification of satellite imagery representing the existence or the percentage of forests in any location on Earth. In this study, Global Phased Arrayed L-band Synthetic Aperture Radar PALSAR-2/PALSAR mosaic and forest/non-forest maps of Japan Aerospace Exploration Agency (JAXA) and Global Forest Cover Change (GFCC) thematic image tiles of National Aeronautics and Space Administration (NASA), which are two of the widely accepted such data, were compared to one another and to our control results produced by a pixel-based classification method to assess the performance of afforestation works around seven major hydroelectric dam reservoirs situated within the central part of Turkey. The results showed that Global PALSAR-2/PALSAR forest/non-forest maps were somewhat capturing the trend, but overly exaggerating the ground facts up to 1064%. GFCC epochs, on the other hand, did not yield sound results in this semi-arid part of Turkey. Latter data could not even capture the successfully afforested sites.
Habitat suitability model with maximum entropy approach for European roe deer (Capreolus capreolus) in the Black Sea Region
(2019-11-01) Evcin O.; Kucuk O.; Akturk E.
Evaluating the relationships between wildlife species and their habitats helps to predict effects of habitat change for present and future management of wild animal populations. Building ecological models are good ways to understand and manage wildlife populations and to predict various environmental scenarios. Recently, management of ungulates is becoming more important in Europe due to a high demand of hunting and their role in biodiversity. European roe deer (Capreolus capreolus) is the smallest species of cervids and has a widespread distribution in Turkey. In this study, two habitat suitability models of roe deers, living in the Black Sea Region in Turkey, were created by using a maximum entropy (MaxEnt) approach. Two wildlife development areas, which have widely different habitat types, were selected as study sites. As a result of this study, area under the curve (AUC) values were found to be above 0.80. According to the modeling results, in two different habitat types, ecological variables are quite similar in general. This study is the first study on modeling European roe deers in Turkey.
How good is TanDEM-X 50 m forest/non-forest map? Product validation using temporally corrected geo-browser supplied imagery through Collect Earth
(2023-01-01) Akturk E.; Altunel A.O.; Atesoglu A.; Seki M.; Erpay S.
TanDEM-X Forest/Non-Forest (FNF) map(s) have been one such data focusing on the status of global forest coverage, which has played an essential role in combating climate change. Although the producers have carried out verification and comparison analyses, the need for accuracy assessments in a broader sense creates uncertainties for the users to approve the new data. For this purpose, TanDEM-X 50 m FNF maps were exclusively examined visually through 66,000 test grids within 30 geocells selected from temperate, boreal, and tropical forest zones. Thus, it was aimed to provide product accuracy utilizing visual inspections to the end users of TanDEM-X FNF maps. In addition, Collect Earth (CE) software was used to evaluate the dataset visually, and its advantages or disadvantages were compared with similarly designed studies. Consequently, even though the producers’ data sets were found to have an accuracy of around 85%, it was observed that there were some issues, especially in the definition of the “non-forest” class. CE software was found to be helpful in such studies. However, the dependence of the analyses on geo-browser supplied imagery had some limitations in estimating the accuracy of a new dataset.
ICESat-2 for Canopy Cover Estimation at Large-Scale on a Cloud-Based Platform
(2023-04-01) Akturk E.; Popescu S.C.; Malambo L.
Forest canopy cover is an essential biophysical parameter of ecological significance, especially for characterizing woodlands and forests. This research focused on using data from the ICESat-2/ATLAS spaceborne lidar sensor, a photon-counting altimetry system, to map the forest canopy cover over a large country extent. The study proposed a novel approach to compute categorized canopy cover using photon-counting data and available ancillary Landsat images to build the canopy cover model. In addition, this research tested a cloud-mapping platform, the Google Earth Engine (GEE), as an example of a large-scale study. The canopy cover map of the Republic of Türkiye produced from this study has an average accuracy of over 70%. Even though the results were promising, it has been determined that the issues caused by the auxiliary data negatively affect the overall success. Moreover, while GEE offered many benefits, such as user-friendliness and convenience, it had processing limits that posed challenges for large-scale studies. Using weak or strong beams’ segments separately did not show a significant difference in estimating canopy cover. Briefly, this study demonstrates the potential of using photon-counting data and GEE for mapping forest canopy cover at a large scale.
Modeling and monitoring riparian buffer zones using LiDAR data in South Carolina
(2020-06-01) Akturk E.; Post C.; Mikhailova E.A.
Functional riparian areas protect water quality and conserve aquatic systems, plants, and wildlife. Laser-based remote sensing technology offers a high-resolution approach to both characterize and document changes in riparian buffer zones (RBZs). The objectives of this study were to demonstrate a rapid method and model to calculate riparian buffer widths on both sides of a stream using a LiDAR-derived slope variable, to classify riparian buffers and determine their quality, and to evaluate the appropriateness of using LiDAR in riparian buffer assessment. For this purpose, RBZs were delineated for Hunnicutt and King Creek, which are located in Oconee and Pickens counties, in South Carolina. Results show that LiDAR was effective in delineating required riparian buffer widths based on the topography slope of upstream areas, and in calculating the ratio of tree cover. This LiDAR-based assessment methodology could be applied to a wide-range of environments.
Monitoring forest canopy cover change with ICESat-2 Data in fire-prone areas: A case study in Antalya, Türkiye
(2023-12-29) Akturk E.
Monitoring of Land- Cover/Land- Use changes in Syria by involving the collect earth methodology approach
(2020-12-01) Atesoglu A.; Akturk E.; Rasouli A.; Erpay S.; Ozel H.B.
Land-cover/Land-use (LC/LU) monitoring is important for the ecosystem and climate change intends. The LC/LU change sector plays and will continue to play a crucial role in international efforts for decision making and planning. Monitoring, evaluating and reporting according to international agreements in LC/LU change is still a challenging task difficult task due to government instability, war or conflict situation in some countries. What happened in Syria in recent years is an example of this situation too. In this context, different methods based on remote sensing are used to produce more sensitive and accurate data. Thus, in this study used to Collect Earth methodology, that multi-purpose land monitoring using remote sensing and Geographic information system integrated, for accurately estimating LC/LU change between 2000 and 2018 in Syria. Recently, The Food and Agriculture Organization (FAO) to assist countries in collecting, managing and analysing land-cover and land-use information have released Open Foris Collect Earth software. Besides, there are not enough and current studies for studies in line with the international LC/LU categories and classification principles in Syria. Overall, the article provides basic results which distribution of LC/LU classes according to the Intergovernmental Panel on Climate Change (IPCC), monitoring the current status and change of forest, pasture or woody vegetation, agricultural fields and wetlands, LC/LU change between 2000-2018, habitat loss-gain and revealing the effects of war on the land.