Browsing by Author "Erkaya, Halil"

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Citation Count: 1
PERFORMANCE ANALYSIS OF WEB-BASED RELATIVE AND PRECISE POINT POSITIONING TECHNIQUES WITH DIFFERENT SATELLITE VISIBILITY CONDITIONS
(Univ Federal Parana, Centro Politecnico, 2020) Albayrak, Muge; Erdogan, Bahattin; Erkaya, Halil; Geomatik Mühendisliği / Geomatics Engineering
The Global Navigation Satellite System (GNSS) is used for precise positioning applications, such as surveying and geodesy. The aim of the present work is to evaluate the effectiveness of web-based relative positioning (RP) and precise point positioning (PPP) GNSS post-processing services using measurements of different satellite visibility obstacles. Within this framework, static GNSS observations were conducted at three control benchmarks selected taking the impact of natural and human-made obstacles on satellite signals into consideration. 3 hours of static GNSS observations in Istanbul, Turkey were repeatedly obtained from three control BMs over six days and were evaluated through two RP (AUSPOS, OPUS) and three PPP (CSRS-PPP, Magic-PPP, GAPS-PPP) web-based GNSS post-processing services. The 6-day average of the three control benchmark coordinates computed using the Bernese GPS software v5.0, and were accepted as true results. They were compared to the local coordinates acquired through the RP and PPP web-based GNSS post-processing services. The different satellite visibility conditions were found to have significant effects on the GNSS point positioning solutions. We also found that web-based GNSS post-processing services provide easy and effective solutions for geodetic positioning applications.
Citation Count: 3
A STATISTICAL EVALUATION OF REGISTRATION METHODS USED IN TERRESTRIAL LASER SCANNING IN CULTURAL HERITAGE APPLICATIONS
(Univ Agean, dept Mediterranean Stud, 2017) Gumus, Kutalmis; Gumus, M. Gizem; Erkaya, Halil; Geomatik Mühendisliği / Geomatics Engineering
Terrestrial laser scanning (TLS) systems are used during surveying in cultural heritage applications, supported by recent developments in the electronics and computing. The aim of this article is to present a statistical study of the accuracy of registration methods (target (sphere), specific point and surface-matching) used for merged of the scans captured from different scan stations. A Mensi GS 100 terrestrial laser scanner was used to scan an historical building. The point clouds reflecting the building facade were registered using these registration methods and were transformed into the same geodesic coordinate system. A Leica TPS 1200 Total Station was used to measure the coordinates of specific points on the building facade and compare them with the coordinates of the same points using three different scan-registration methods. The t-student test and Analysis of Variance (ANOVA) were used for point-and method-based comparisons, and it was found that the coordinates did not exhibit any statistically significant variation. Better results were obtained with target-based registration methods compared to other methods, and with surface-matching methods compared to methods using specific points. Although the results of the registration methods used in this study had certain similarities, variation in their accuracy was determined to be statistically significant.