Browsing by Author "Altunel, AO"
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Web of Science Accuracy assessment of a low-cost UAV derived digital elevation model (DEM) in a highly broken and vegetated terrain(2019.01.01) Akturk, E; Altunel, AOWeb of Science Capturing the level of progress in vertical accuracy achieved by ASTER GDEM since the beginning: Turkish and Nigerian examples(2022.01.01) Altunel, AO; Okolie, CJ; Kurtipek, APublication Determination of Some Stand and Site Parameters Influencing the Snow Damage in Trees: A Case Study of Boyabat Forest Enterprise, Turkey(2019.01.01) Altunel, AO; Arif Oğuz ALTUNELAim of Study: Determination of the snow damage triggering stand and site parameter on trees.Area of Study: Damaged compartments of Yedicam and Burnuk Forest Directorates, #234 and #116, within Boyabat Forest Enterprise of Kastamonu Regional Directorate of Forestry.Material and Method: Two damaged and two control compartments from each directorate were compared to find if any site or stand parameters are related to the snow damage occurred in the area during 2014-2015 winter. Statistical analysis were carried out to test the significance of the parameters.Main results: Age, relative density, the number of trees, basal area and stand volume of the stand parameters, and slope, site class, terrain roughness and soil depth of the site parameters were statistically linked to the snow damage.Research highlights: The climate is a force to be reckoned with. New strategies must be devised and put into action in forest management. Studies have shown the mishaps. The lessons should be taken from the past experiences. Apparent mistakes must gradually be eliminated.Web of Science Web of Science Determining the habitat fragmentation thru geoscience capabilities in Turkey: A case study of wildlife refuges(2021.01.01) Altunel, AO; Caglar, S; Altunel, TWeb of Science Effects of environmental factors and forest management on landscape-scale forest storm damage in Turkey(2020.01.01) Torun, P; Altunel, AOWeb of Science ESTIMATING ABOVE-GROUND CARBON BIOMASS USING SATELLITE IMAGE REFLECTION VALUES: A CASE STUDY IN CAMYAZI FOREST DIRECTORATE, TURKEY(2015.01.01) Aricak, B; Bulut, A; Altunel, AO; Sakici, OEWeb of Science Evaluation of TanDEM-X 90 m Digital Elevation Model(2019.01.01) Altunel, AOPublication Evaluation of TanDEM-X 90 m Digital Elevation Model(2019-04-03) Altunel A.; Altunel, AOGerman Aerospace Center (DLR), EADS Astrium GmbH and Infoterra GmbH alliance came up with the idea of taking DTED-2 (Digital terrain elevation data, level-2) specifications to even higher standard of HRTE-3 (High resolution terrain elevation, level-3) in 2006, as a result TDX (TerraSAR-X, TanDEM-X) constellation was born. The mission was geared to create a rather sensitive, high precision 3 dimensional map of the entire Earth in seamless and very high quality. After Shuttle Radar Topography Mission (SRTM) in 2000 and its derivatives, along with numerous prior and subsequent other similar data, have practically set the standard for defining the topographical surfaces in global scale, the twin satellites acquired all of Earth’s land surfaces numerous times to produce varying resolution digital elevation models (DEM) between 2011 and late 2015. DEMs are widely used in many planning, decision making and engineering related projects. They provide sound backing for mankind’s endeavors. Ground resolution is the most sought after feature of any DEM. Finer resolution is usually associated with a better surface definition. Recently, an entirely new global DEM has been released DLR. The 90 m DEM is the latest variant derived from such an undertaking. This study aimed to examine the overall effectiveness of this alleged new data in four previously surveyed locations and against the performances of finer SRTM 1- and comparable SRTM 3 arc second data. The results showed that TanDEM-X 90 m data overestimated. They seemed to be rather accurate in flat to slightly undulating terrain, but overestimated in broken to treacherous terrain than both SRTMs. Root Mean Square Error was greater in site one and site four, and lower in site two and site three compared to both SRTM 1 and SRTM 3 arc second data.Web of Science Examining the PALSAR-2 Global forest/non-forest maps through Turkish afforestation practices(2020.01.01) Altunel, AO; Akturk, E; Altunel, TWeb of Science 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, AO; Atesoglu, A; Seki, M; Erpay, SWeb of Science Publication Questioning the effects of raster-resampling and slope on the precision of TanDEM-X 90 m digital elevation model(2021-01-01) Altunel A.O.; Altunel, AODefining watersheds with enough topographical features is crucial when large infrastructure projects are concerned. German Aerospace Center (DLR) recently announced the dissemination of the 90 m variant of the original global TanDEM-X 12 m Digital elevation model (DEM). It was announced as produced with a special averaging technique, which would even surpass the precision of the 12 m DEM. This study aimed to test this claim while simultaneously testing whether resolution coarsening would deteriorate the performance of a higher precision DEM. AW3D30 was used as auxiliary data in four sites. Results confirmed that the 90 m DEM was indeed highly reliable at or below 20% slopes in two investigated dam reservoir areas with gentle terrain conditions, and overestimated in other two dam reservoirs with severe topography. The resampling approach did not necessarily worsen the elevation values aggregated into a larger raster resolution as obvious from the auxiliary data analyses.Web of Science Suitability of open-access elevation models for micro-scale watershed planning(2018.01.01) Altunel, AOPublication Suitability of open-access elevation models for micro-scale watershed planning.(2018-08-10T00:00:00Z) Altunel, Arif Oguz; Altunel, AOWatershed planning is a major issue in Turkey and other parts of the world. Surrounded by seawater on almost three-quarters of its international borders and by sheer mountains along the coastal regions and throughout the country, Turkey experiences a range of climatic changes, which constantly shape its topography. Recently, the occurrences of floods, landslides, and torrents have increased, forcing decision-makers to come up with solutions to manage and rehabilitate the upper watersheds in order to stop or limit the impact of disasters on downstream areas. Possible solutions should reduce flow coefficients, erosion, and sedimentation and increase reservoir capacities. It is expected that torrent volumes will decrease, drainage regimes on slopes will be better organized and adjusted, thawing snow will be better deposited and delayed, evapotranspiration will increase, surface runoffs will be delayed, and water regimes will be better managed, meaning that flood and torrent control will be achieved. For the reasons mentioned above, watershed parameters need to be firmly set. In the scope of this study, the elevation, slope acreage, and reservoir capacity of a small watershed, as extracted from open-access elevation models, were compared to a real-time kinematic (RTK) global positioning system (GPS)-generated point cloud and the resulting elevation model through various geospatial and analytical means. The Shuttle Radar Topography Mission (SRTM) C-band digital elevation model (DEM) (version 3) proved to be a satisfactory method in making residual, correlation, mean, and reservoir capacity comparisons. An L-band Advanced Land Observing Satellite (ALOS) phased-array-type synthetic aperture radar (PALSAR) and an X-band DLR_SRTM ASTER were slightly superior methods in terms of defining a greater number of slope categories than the other models. Finally, DLR_SRTM and SRTMv3 could match a greater number of slope façades than the other models. Seventeen years after its acquisition, SRTM and its derivatives have continued leading the topographic definition of the Earth.Publication The effect of DEM resolution on topographic wetness index calculation and visualization: An insight to the hidden danger unraveled in Bozkurt in August, 2021(2023-07-05) Altunel A.O.; Altunel, AOTopographic Wetness Index, also known as the compound topographic index, (TWI) is a topographic indicator that calculates the potential of where water is likely to accumulate during excessive precipitation cycles resulting from abrupt atmospheric anomalies. High index values represent serious potential of water accumulation due to low slope, and the opposite for high slope. As expected from the term, slope, Digital Elevation Model (DEM) datasets play an important role in the calculation of TWI. DEMs are produced utilizing tachometry, GPS benchmarking, UAV, aerial or satellite image capture and LIDAR capabilities. However, no matter how it is generated, a DEM is as good as the actual ground sampling algorithm, on which the final resolution is based. Using six different DEM resolutions coming from three global and one national source presented in three different setting coverages, upper feeder basin of Bozkurt sub-province, Kastamonu, was analyzed emphasizing the urbanized part of the sub-province, which was devastated during the August 11th, 2021 flood. Coarser resolution missed the overall precision while the finer resolution captured it nicely. On the flip side, finer resolution excessively fragmented the questioned area while the coarser resolution formed a unity coinciding with the destructed area recorded during the event.Web of Science The effect of population shift on land cover change and illegal forest activities(2021.01.01) Guloglu, Y; Bulut, A; Altunel, AO; Bayramoglu, MMWeb of Science Tracing the culprits over the destruction of three coastal communities during a rouge rainstorm on August 2021 in north central Turkiye(2023.01.01) Altunel, AO; Kara, FWeb of Science Visibility analysis of fire lookout towers in the Boyabat State Forest Enterprise in Turkey(2017.01.01) Kucuk, O; Topaloglu, O; Altunel, AO; Cetin, M