Murat Oruç

Accuracy assessment of interferometric digital elevation models derived from the Shuttle Radar Topography Mission X- and C-band data in a test area with rolling topography and moderate forest cover

In February 2000, the Shuttle Radar Topography Mission (SRTM) mapped large areas of the global landmass using two radar systems operating simultaneously in X and C band. The radar mapping instrument consisted of modified versions of the SIR-C C-band and X-band radars flown on the shuttle in 1994. Modifications included a 60-m retractable boom, with C-band and X-band receive-only antennas attached to the booms end. High-accuracy metrology systems were added to measure position and attitude of the shuttle and the positions of the boom antennas. The dual apertures at each band form radar interferometers suitable for making high-accuracy topographic maps of the Earth. The C-band data set is being processed by JPL for the archives of the National Imagery and Mapping Agency and the National Aeronautics and Space Administration. The X-band data set is processed and distributed at DLR, Germany. This paper deals with the accuracy assessments of the interferometric DEMs derived from the X- and C-band synthetic aperture radar systems over a testfield with rolling topography and moderate forest cover using the reference DEM digitized from the topographic maps of 1:25,000 scale. Obtained results for the two interferometric DEMs are similar and lie in the range of 10–11 m. The accuracy of SRTM X- and C-band DEMs was also checked against ground control points measured by differential GPS, and the rms height errors were found to be about 9 m, which confirms the results based on the reference DEM.

Combined Efficiency of RPC and DEM Accuracy on Georeferencing Accuracy of Orthoimage: Case Study With Pléiades Panchromatic Mono Image

Generation of orthoimages in remote sensing and photogrammetry is a common and sometimes mandatory issue. The desired georeferencing accuracy of the orthoimage depends on two main factors: accuracy of transformation parameters and density and accuracy of height information. The objective of this letter is to estimate the combined efficiency of accuracies of refined rational polynomial coefficients and digital elevation models on georeferencing accuracy of the orthoimage utilizing the figure condition method (FCM). In this letter, details of the method, the characteristics of the evaluated Pléiades panchromatic mono image and auxiliary data, and also the test site are presented. The findings were compared with other results from high-resolution satellite images such as those from IKONOS, QuickBird, and OrbView-3. It is observed that the FCM might be preferred to estimate the overall georeferencing accuracy of an orthoimage, reaching ± 0.3-2.7-pixel accuracy range. The Pléiades panchromatic mono image presents almost equal accuracy as the compared images. The research was carried out on the Zonguldak (Turkey) test site which has mountainous and extremely undulating topography.

Geometric Accuracy Evaluation of the DEM Generated by the Russian TK-350 Stereo Scenes Using the SRTM X- and C-band Interferometric DEMs

TK-350 stereo-scenes covering 200 km � 300 km on the ground with a base-to-height-ratio of 0.52 have been analysed on Zonguldak testfield in the northwest of Turkey. The pixel size on the ground is 10 m. Control points digitised from 1:25 000 scale topographic maps have been used in the test. The sensor orientation was executed by the PCI Geomatica ® V8.2 software package. TK-350 stereo-images can yield 3D geopositioning to an accuracy of about 10 m horizontally and 17 m vertically. Based on this orientation, DEM with 40 m cell size was generated by the related module of PCI system. For the validation of extracted DEM, matched data was checked against the interferometric DEMs from SRTM X- and C-band SAR data. Based on this comparison, the RMSE of Z values was found to be in the range of 25.6 to 36.9 m and 28.7 to 38.7 m outside and inside the forest area, respectively. However, accuracy results obtained against the SRTM C-band DEM are more representative than those of X-band since the coverage of C-band DEM on the interest area is larger than the X-band. There are some systematic shifts of the TK-350 DEM against the SRTM DEMs which lie between the 3.7 m to 6.2 m which is probably due to the different sensor orientation of TK-350 and SRTM datasets. Height discrepancies are also analysed as a function of terrain slope. It was found that slope depending components were always larger in the case of C-band DEM because of its larger cell spacing. In the forest areas, more dependency upon the slope was observed against the open areas.

Pan-sharpening quality investigation of PLÉIADES-1A images

Abstract Optical remote sensing satellites obtain MS and Pan images simultaneously over the same coverage area. Remote sensing and image processing communities are working on different pan-sharpening methods capable of taking advantage of MS and Pan images. Each remote sensing system has its own advantages and disadvantages, leading to the question ‘Which pan-sharpening method should be used for which type of imagery?’ The aim of this research is to investigate the pan-sharpening performance of PLÉIADES-1A images. For this purpose, pan-sharpened images were generated using PCA, IHS and Brovey Transform which are the most popular pan-sharpening methods. Then, the pan-sharpened images were evaluated quantitatively using Correlation Coefficient, Root Mean Square Error, Relative Average Spectral Error, Spectral Angle Mapper and Erreur Relative Globale Adimensionnelle de Synthése. In addition, pan-sharpened images were evaluated qualitatively by taking object availability and completeness into consideration.