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An application of roll-invariant polarimetric features for crop classification from multi-temporal RADARSAT-2 SAR data

Ustuner M. | Sanli F.B. | Abdikan S. | Esetlili M.T. | Bilgin G.

Conference Object | 2018 | International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives42 ( 1 ) , pp.451 - 456

Crops are dynamically changing and time-critical in the growing season and therefore multitemporal earth observation data are needed for spatio-temporal monitoring of the crops. This study evaluates the impacts of classical roll-invariant polarimetric features such as entropy (H), anisotropy (A), mean alpha angle (?¯) and total scattering power (SPAN) for the crop classification from multitemporal polarimetric SAR data. For this purpose, five different data set were generated as following: (1) H?¯, (2) H?¯Span, (3) H?¯A, (4) H?¯ASpan and (5) coherency [T] matrix. A time-series of four PolSAR data (Radarsat-2) were acquired as 13 Jun . . .e, 01 July, 31 July and 24 August in 2016 for the test site located in Konya, Turkey. The test site is covered with crops (maize, potato, summer wheat, sunflower, and alfalfa). For the classification of the data set, three different models were used as following: Support Vector Machines (SVMs), Random Forests (RFs) and Naive Bayes (NB). The experimental results highlight that H?ASpan (91.43% for SVM, 92.25% for RF and 90.55% for NB) outperformed all other data sets in terms of classification performance, which explicitly proves the significant contribution of SPAN for the discrimination of crops. Highest classification accuracy was obtained as 92.25% by RF and H?ASpan while lowest classification accuracy was obtained as 66.99% by NB and H?. This experimental study suggests that roll-invariant polarimetric features can be considered as the powerful polarimetric components for the crop classification. In addition, the findings prove the added benefits of PolSAR data investigation by means of crop classification. © Authors 2018. CC BY 4.0 License Daha fazlası Daha az

Comparison of information contents of high resolution space images

Topan H. | Büyüksalih G. | Jacobsen K.

Conference Object | 2004 | International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives35 , pp.451 - 456

The information contents of high resolution space images, usable for mapping, are not only depending upon the image resolution that means in case of digital data, depending upon the pixel size in the object space. Important is also the contrast, the spectral range, radiometric resolution and colour beside the atmospheric condition and the object contrast. From the area of Zonguldak, Turkey different space images are available like taken by IKONOS, KVR-1000, SPOT 5, IRS-1C, TK350, ASTER, Landsat TM, JERS and SRTM X-band. Of course the information content is mainly depending upon the pixel size on the ground, but this is still quite d . . .ifferent for the RADAR images taken by JERS and SRTM. The object identification in these images disturbed by speckle cannot be compared with optical images having the same pixel size. There is a rule of thumb for the relation of the pixel size to the possible map scale, but it cannot be used for ground pixels with a size exceeding 5m because this is leading to a loss of important information which must be available also in small scale maps. The limited radiometric resolution of IRS-1C images is still a disadvantage, especially in dark and shadow areas. The KVR-1000 available with 1.4m pixel size cannot be compared directly with the information contents which should be included with this resolution. The colour information of IKONOS supports the object identification, so the 4m ground pixel size includes a higher information contents like a panchromatic image with the same resolution and the object identification is quite easier. With IKONOS pan sharpened images maps up to a scale 1 : 7000 can be created. © 2004 International Society for Photogrammetry and Remote Sensing. All rights reserved Daha fazlası Daha az

Topographic estimation by terrasar-X

Sefercik U.G. | Soergel U.

Conference Object | 2010 | International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives38 , pp.504 - 510

SAR Interferometry (InSAR) is a technique to derive Digital Elevation Model (DEM) from at least two complex SAR images. The data are either taken simultaneously (single-pass mode) or sequentially (repeat-pass mode) by airborne or space-born sensors (carriers: plane, satellite, shuttle etc.). To date, one of the most important single-pass interferometry measurement campaigns is the Shuttle Radar Topography Mission (SRTM) completing its mission successfully after 11 days of operation between 11th and 22nd of February 2000. On the other hand, repeat-pass InSAR has been used by several satellite systems: ENVISAT, ERS 1-2, RADARSAT 1-2, . . .ALOS, JERS-1 etc. One of the most advanced systems is the German TerraSAR-X (TSX) satellite launched on June 15th , 2007. TSX offers high resolution (~1m by Spotlight mode) imagery which could not been achieved from radar technologies up to this time similar to high resolution optical imagery. In contrast to optical sensors, TSX can be operated under all weather conditions without being influenced by clouds. The data sets provided by TSX newly obtained by scientific community and evaluations are currently being performed. As mentioned above, utilizing the advantages of SAR technology, indeed the planimetric locations of target ground objects, elevations of them can be determined using interferometry. Through the interferometric data, interferograms (fringe maps) can be generated and applying interferometric processing steps height models can be created for large coverage interest areas. The main targets of this investigation can be summarized as; generation of height models derived from TSX InSAR image-pairs and evaluation by comparison with more accurate reference height models as well as height models based on high resolution optical satellite images. Absolute and relative accuracy, stability, homogeneity and dependency upon various parameters are determined. The approach will be demonstrated using TSX data covering Istanbul area, Turkey Daha fazlası Daha az

Urban modelling performance of next generation SAR missions

Sefercik U.G. | Yastikli N. | Atalay C.

Conference Object | 2017 | International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives42 ( 2W7 ) , pp.641 - 646

In synthetic aperture radar (SAR) technology, urban mapping and modelling have become possible with revolutionary missions TerraSAR-X (TSX) and Cosmo-SkyMed (CSK) since 2007. These satellites offer 1m spatial resolution in high-resolution spotlight imaging mode and capable for high quality digital surface model (DSM) acquisition for urban areas utilizing interferometric SAR (InSAR) technology. With the advantage of independent generation from seasonal weather conditions, TSX and CSK DSMs are much in demand by scientific users. The performance of SAR DSMs is influenced by the distortions such as layover, foreshortening, shadow and do . . .uble-bounce depend up on imaging geometry. In this study, the potential of DSMs derived from convenient 1m high-resolution spotlight (HS) InSAR pairs of CSK and TSX is validated by model-to-model absolute and relative accuracy estimations in an urban area. For the verification, an airborne laser scanning (ALS) DSM of the study area was used as the reference model. Results demonstrated that TSX and CSK urban DSMs are compatible in open, built-up and forest land forms with the absolute accuracy of 8-10 m. The relative accuracies based on the coherence of neighbouring pixels are superior to absolute accuracies both for CSK and TSX Daha fazlası Daha az

DEM generation with WorldView-2 images

Büyüksalih G. | Baz I. | Alkan M. | Jacobsen K.

Conference Object | 2012 | International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives39 , pp.203 - 207

For planning purposes 42km coast line of the Black Sea, starting at the Bosporus going in West direction, with a width of approximately 5km, was imaged by WorldView-2. Three stereo scenes have been oriented at first by 3D-affine transformation and later by bias corrected RPC solution. The result is nearly the same, but it is limited by identification of the control points in the images. Nevertheless after blunder elimination by data snooping root mean square discrepancies below 1 pixel have been reached. The root mean square discrepancy at control point height reached 0.5m up to 1.3m with a base to height relation between 1:1.26 and . . . 1:1.80. Digital Surface models (DSM) with 4m spacing have been generated by least squares matching with region growing, supported by image pyramids. A higher percentage of the mountainous area is covered by forest, requiring the approximation based on image pyramids. In the forest area the approximation just by region growing leads to larger gaps in the DSM. Caused by the good image quality of WorldView-2 the correlation coefficients reached by least squares matching are high and even in most forest areas a satisfying density of accepted points was reached. Two stereo models have an overlapping area of 1.6 km times 6.7km allowing an accuracy evaluation. Small, but nevertheless significant differences in scene orientation have been eliminated by least squares shift of both overlapping height models to each other. The root mean square differences of both independent DSM are 1.06m or as a function of terrain inclination 0.74m + 0.55m* tangent (slope). The terrain inclination in the average is 7° with 12% exceeding 17°. The frequency distribution of height discrepancies is not far away from normal distribution, but as usual, larger discrepancies are more often available as corresponding to normal distribution. This also can be seen by the normalized medium absolute deviation (NMAS) related to 68% probability level of 0.83m being significant smaller as the root mean square differences. Nevertheless the results indicate a standard deviation of the single height models of 0.75m or 0.52m + 0.39* tangent (slope), corresponding to approximately 0.6 pixels for the x-parallax in flat terrain, being very satisfying for the available land cover. An interpolation over 10m enlarged the root mean square differences of both height models nearly by 50% Daha fazlası Daha az

Effects of ocean tide models on GNSS-estimated ZTD and PWV in Turkey

Gurbuz G. | Jin S. | Mekik C.

Conference Object | 2015 | International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives40 ( 1W5 ) , pp.255 - 258

Global Navigation Satellite System (GNSS) observations can precisely estimate the total zenith tropospheric delay (ZTD) and precipitable water vapour (PWV) for weather prediction and atmospheric research as a continuous and all-weather technique. However, apart from GNSS technique itself, estimations of ZTD and PWV are subject to effects of geophysical models with large uncertainties, particularly imprecise ocean tide models in Turkey. In this paper, GNSS data from Jan. 1st to Dec. 31st of 2014 are processed at 4 co-located GNSS stations (GISM, DIYB, GANM, and ADAN) with radiosonde from Turkish Met-Office along with several nearby I . . .GS stations. The GAMIT/GLOBK software has been used to process GNSS data of 30-second sample using the Vienna Mapping Function and 10° elevation cut-off angle. Also tidal and non-tidal atmospheric pressure loadings (ATML) at the observation level are also applied in GAMIT/GLOBK. Several widely used ocean tide models are used to evaluate their effects on GNSS-estimated ZTD and PWV estimation, such as IERS recommended FES2004, NAO99b from a barotropic hydrodynamic model, CSR4.0 obtained from TOPEX/Poseidon altimetry with the model FES94.1 as the reference model and GOT00 which is again long wavelength adjustments of FES94.1 using TOPEX/Poseidon data at 0.5 by 0.5 degree grid. The ZTD and PWV computed from radiosonde profile observations are regarded as reference values for the comparison and validation. In the processing phase, five different strategies are taken without ocean tide model and with four aforementioned ocean tide models, respectively, which are used to evaluate ocean tide models effects on GNSS-estimated ZTD and PWV estimation through comparing with co-located Radiosonde. Results showed that ocean tide models have greatly affected the estimation of the ZTD in centimeter level and thus the precipitable water vapour in millimeter level, respectively at stations near coasts. The ocean tide model FES2004 that is the product of assimilation of the altimetric data of ERS2, TOPEX/POSEIDON and the data of a global tide gauge network, gave the most accurate results when compared to radiosonde with ±1.99 mm in PWV at stations near coastline. While other ocean tides models agree each other at millimeter level in PWV. However, at inland GNSS stations, ocean tide models have less effects on GNSS-estimated ZTD and PWV, e.g., with ±1.0 mm in ZTD and ±0.1 mm in PWV Daha fazlası Daha az

Spatial and temporal analysis of forest covers change: Human impacts and natural disturbances in Bartin Forests, NW of Turkey

Atesoglu A. | Tunay M. | Buyuksalih G.

Conference Object | 2004 | International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives35 , pp.255 - 258

During last two decades, Bartin Forests in northwest of Turkey have been exploited by human impacts. Easy access and the abundance of valuable and large diversity forest products have led to higher population densities with opening new settlement areas via deforestation activities. In this study, interpretation of digital image classification resulted from multi-date Landsat-5 TM images recorded in time frame between 1992s and 2000s was evaluated to produce land cover maps for change detection analysis. The accuracy of the Landsat TM classification and errors inherent to the techniques used were assessed accordingly. The updated dig . . .ital forest inventory plans, existing different scales topographic maps and aerial photographs was integrated into a GIS database with the generated classification results in order to elaborate a spatially explicit multi-date database on land use/cover change. This spatial model is used for identifying deforestation fronts and biodiversity conservation. As a result, several changes in the test site were observed, including increases in the areas extent of agriculture lands and urbanization with the corresponding decrease in Bartin Forest's wealth. © 2004 International Society for Photogrammetry and Remote Sensing. All rights reserved Daha fazlası Daha az

A multi-source data approach for the investigation of land subsidence in the Konya basin, Turkey

Calò F. | Notti D. | Galve J.P. | Abdikan S. | Görüm T. | Orhan O. | Makineci H.B.

Conference Object | 2018 | International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives42 ( 3W4 ) , pp.129 - 135

Groundwater depletion caused by rapid population growth, global climate change, water resources overexploitation is a major concern in many regions of the world. Consequences are not limited to a non-renewable water loss but extend to environmental degradation and geo-hazards risk increase. In areas where excessive groundwater withdrawal occurs, land subsidence induced by aquifer compaction is observed, resulting in severe socio-economic damage for the affected communities. In this work, we apply a multi-source data approach to investigate the fragile environment of Konya plain, central Turkey. The area, which is under strong anthro . . .pogenic pressures and faces with serious water-related problems, is widely affected by land subsidence. In order to analyze the spatial and temporal pattern of the subsidence process we use the Small BAseline Subset DInSAR technique to process two datasets of ENVISAT SAR images spanning the 2002-2010 period and to produce ground deformation maps and associated time-series. Results, complemented with meteorological, stratigraphic and piezometric data as well as with land-cover information, allow us to obtain a comprehensive picture of the climatic, hydrogeological and human dynamics of the study area. © Authors 2018. CC BY 4.0 License Daha fazlası Daha az

A multidisciplinary landslide case study: Devrek landslide

Gormus K.S. | Kutoglu S.H. | Gurbuz G. | Capar O.F. | Akgul V.

Conference Object | 2018 | International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives42 ( 3W4 ) , pp.227 - 230

Landslides are one of the leading causes of loss of life and property in the World. Landslides are the most profound ones within other mass movements. Especially in the Northern region of Turkey is severely threatened by landslides. Mass movements can be divided several main classes which are falls, slides, creeps, flows and complex movements. Landslides can occur due to a variety of reasons and most basic one of them is the angle of repose or slope of the hillside. If the angle is overly steep, gravity will pull the material downward, causing a mass movement. Many studies have been carried out in Turkey to monitor landslides, preve . . .nt and reduce landslides damage. These studies mostly focused on forecasting of landslides and damage determination after landslides. Activities required to be carried out in the field can be resulted with unwanted consequences for work safety while the landslide is still active. A landslide is triggered at Devrek, Zonguldak on July 16th, 2015 which affected an area of 40 hectares. For this reason, 88 buildings and a school are evacuated by authorities. To support emergency action plan while ongoing active landslide occurrence at Devrek, apart from the geotechnical approach, aerial photogrammetry, terrestrial laser scanning, land-based SAR methods are used. This study is a summary of studies carried out simultaneously with an active landslide at Devrek, Zonguldak on July 20th - August 8th, 2015. © Authors 2018. CC BY 4.0 License Daha fazlası Daha az

DEM generation with short base length pleiades triplet

Jacobsen K. | Topan H.

Conference Object | 2015 | International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives40 ( 3W2 ) , pp.81 - 86

An image triplet of Pleiades images covering the area of Zonguldak, Turkey has been investigated. The height to base relation of the first to the last image is just 1:4.5 and for the first and the second image 1:9. This is quite below the usual height to base relation of 1:1.6 for a typical stereo pair of space images. The corresponding small angle of convergence influences the possible vertical accuracy, but images with such a small angle of convergence are more similar to each other as images with larger convergence angles. This enables a better image matching, improving the vertical accuracy and compensating partially the influen . . .ce of poor intersection geometry. Even over forest areas no matching gaps occurred. Height models are generated with different base configurations and compared with a reference height model. Pleiades images are distributed with 50cm ground sampling distance instead of the physical size of 70cm, the image quality justifies this zooming and also the geometric results are in the range of other space images with originally 50cm GSD. The image orientation by bias corrected Rational Polynomial Coefficients (RPC) is leading with more as 160 ground control points (GCP) to root mean square (RMS) differences slightly below 1.0 GSD of the distributed images (0.5m GSD). Only negligible systematic errors have been identified. With the combination of the first and last image a standard deviation of the generated height model of 1.6m, respectively for flat terrain close to 1.0m has been reached in relation to a reference height model. The small angle of convergence is not as much influencing the height accuracy as according to simple geometric relation Daha fazlası Daha az

Spatial and temporal GIS analysis of change detection using IKONOS images: A case study of Zonguldak

Alkan M. | Oruç M. | Kayabaşi D. | Uga S.

Conference Object | 2015 | International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives38 ( 1W17 ) , pp.81 - 86

Nowadays, remotely sensed images are used for various purposes in different applications. One of them is the change detection using high resolution satellite imagery which is city areas. Urbanization rapid land use and land cover change has taken place in many cities of Turkey as well as in the world in the last 50 years. In this context, comparison of extraction results from these images and existing vector data is the most important issue. The goal here is to show the advantages and disadvantages of the two IKONOS images for creating road and building database and also updating to the database. In this study, high resolution IKONO . . .S 2002 and IKONOS 2008 have been chosen for the test area of the Zonguldak city. Firstly, pan-sharpened IKONOS images have been produced by fusion of high resolution PAN and MS images using PCI Geomatica v9.1 software package. The parcel, building and road network objects from these datasets have been extracted automatically by initially dividing it into the segments and then, they have been classified by using the spectral, spatial and contextual information using eCognition v4.0.6 software package. On the other hand, these objects have been manually digitized from high resolution images using ArcGIS v9.3 software package. These vectors produced automatically and manually have been compared with the existing digital cadastral maps and reference vector maps of scale 1/5000 of test area. The success of object-oriented image analysis results was tested by GIS software; the results have been presented and commented. Therefore, making GIS-based analysis and comparisons with raster and vector data of the test area has crucial importance in terms of putting forth the recent situation Daha fazlası Daha az

Investigaton of sea level change along the Black Sea coast from tide gauge and satellite altimetry

Avsar N.B. | Kutoglu S.H. | Jin S. | Erol B.

Conference Object | 2015 | International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives40 ( 1W5 ) , pp.67 - 71

In this study, we focus on sea level changes along the Black Sea coast. For this purpose, at same observation period the linear trends and the components of seasonal variations of sea level change are estimated at 12 tide gauge sites (Amasra, Igneada, Trabzon-II, Sinop, Sile, Poti, Batumi, Sevastopol, Tuapse, Varna, Bourgas, and Constantza) located along the Black Sea coast and available altimetric grid points closest to the tide gauge locations. The consistency of the results derived from both observations are investigated and interpreted. Furthermore, in order to compare the trends at the same location, it is interpolated from the . . . trends obtained at the altimetric grid points in the defined neighbouring area with a diameter of 0.125° using a weighted average interpolation algorithm at each tide gauge site. For some tide gauges such as Sevastopol, Varna, and Bourgas, it is very likely that the trend estimates are not reliable because the time-spans overlapping the altimeter period are too short. At Sile, the long-term change for the time series of both data types do not give statistically significant linear rates. However, when the sites have long-term records, a general agreement between the satellite altimetry and tide gauge time series is observed at Poti (~20 years) and Tuapse (~18 years). On the other hand, the difference of annual phase between satellite altimetry and tide gauge results is from 1.32° to 71.48° Daha fazlası Daha az

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