Browsing by Subject "GPS"

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Başarsoft ve Türkiye'de navigasyonun evrimi
(Bilkent University, 2023) Elmacı, Oğuzhan Başar; Çapraz, Elif Şevval; Lütem, Selin; Kutay, Gökay Batu; Erdoğan, Ömer
Bu makalenin amacı, Türkiye'de navigasyon sistemlerinin geliştirmelerinin, ve amaclarinin daha iyi anlamak, ayrıca Türkiye'nin harita sistemlerinin Piri Reis'in Kitab-ı Bahriye'sinden Başarsoft'un Google ve Yandex ile ortaklığına, haritalar ve navigasyon yapmaya nasıl geçtiğini araştırmaktır. Bu arastirma ,Türkiye'nin en önemli navigasyon sistemi tabanlı şirketlerinden biri olan Başarsoft'un kurucularından biri olan Ahmet Dabanlı ile röportaj yapılarak gerceklestirildi. Başarsoft'un kurulmasıyla Türkiye, “Küresel Konumlandırma Sistemi” (GPS) sahnesine geç kaldığı için Türkiye için navigasyon ve haritalama sisteminde yeni hedeflere ulaşabildi, ve bu sistemleri, tüm Türkiye vatandaşları için erişilebilir, kolay ve etkili oldugunu gosterdi. Başarsoft, navigasyon sistemlerini ve uygulamalarını sürekli geliştirerek Türkiye'de büyük bir isim yaptı ve bu yazıda daha ayrıntılı olarak incelenecektir.
Open Access
Performance of GPS slant total electron content and IRI-Plas-STEC for days with ionospheric disturbance
(KeAi Communications Co., 2016) Arikan, F.; Shukurov, S.; Tuna, H.; Arıkan, Orhan; Gulyaeva, T. L.
Total Electron Content (TEC) is an important observable parameter of the ionosphere which forms the main source of error for space based navigation and positioning systems. Since the deployment of Global Navigation Satellite Systems (GNSS), cost-effective estimation of TEC between the earth based receiver and Global Positioning System (GPS) satellites became the major means of investigation of local and regional disturbance for earthquake precursor and augmentation system studies. International Reference Ionosphere (IRI) extended to plasmasphere (IRI-Plas) is the most developed ionospheric and plasmaspheric climatic model that provides hourly, monthly median of electron density distribution globally. Recently, IONOLAB group (www.ionolab.org) has presented a new online space weather service that can compute slant TEC (STEC) on a desired ray path for a given date and time using IRI-Plas model (IRI-Plas-STEC). In this study, the performance of the model based STEC is compared with GPS-STEC computed according to the estimation method developed by the IONOLAB group and includes the receiver bias as IONOLAB-BIAS (IONOLAB-STEC). Using Symmetric Kullback-Leibler Distance (SKLD), Cross Correlation (CC) coefficient and the metric norm (L2N) to compare IRI-Plas-STEC and IONOLAB-STEC for the month of October 2011 over the Turkish National Permanent GPS Network (TNPGN-Active), it has been observed that SKLD provides a good indicator of disturbance for both earthquakes and geomagnetic storms.
Open Access
Regularized estimation of TEC from GPS data for certain midlatitude stations and comparison with the IRI model
(Elsevier BV, 2007) Arikan, F.; Arıkan, Orhan; Erol, C. B.
Regularized estimation of Total Electron Content (Reg-Est) is a novel technique which can combine signals from all the satellites for a given instant and given station and estimate the vertical TEC (VTEC) values for any desired period without missing any important features in the temporal or spatial domain. The preprocessed signals from all the satellites that are received for a certain time period are weighted according to their positions with respect to the local zenith. A two step regularization algorithm combines these signals and provides smooth VTEC estimates for the desired time period which can be as short as half an hour or as long as 24 h. The estimation algorithm is tried on VTEC values obtained from six midlatitude stations for the quiet and disturbed days of October, 2003. Within this period, the same estimation parameter set is used for all stations and time periods. When the regularized estimation results are compared with those from IRI-2001, JPL, CODE, UPC and ESA, best accordance is observed with JPL, UPC and CODE estimates. IRI computations usually provide a better fit for the night values. It is observed that the results from the regularized estimation algorithm are highly accurate in detecting disturbances and irregularities for various time scales and stations.
Open Access
Regularized estimation of vertical total electron content from global positioning system data
(Wiley-Blackwell Publishing, 2003) Arikan, F.; Erol, C. B.; Arıkan, Orhan
A novel regularization technique which can combine signals from all Global Positioning System (GPS) satellites for a given instant and a given receiver is developed to estimate the vertical total electron content (VTEC) values for the 24-hour period without missing any important features in the temporal domain. The algorithm is based on the minimization of a cost function which also includes a high pass penalty filter. Optional weighting function and sliding window median filter are added to enrich the processing and smoothing of the data. The developed regularized estimation algorithm is applied to GPS data for various locations for the solar maximum week of 23-28 April 2001. The parameter set that is required by the estimation algorithm is chosen optimally using appropriate error functions. This robust and optimum parameter set can be used for all latitudes and for both quiet and disturbed days. It is observed that the estimated TEC values are in general accordance with the TEC estimates from other global ionospheric maps, especially for quiet days and midlatitudes. Owing to its 30 s time resolution, the regularized VTEC estimates from the developed algorithm are very successful in representation and tracking of sudden temporal variations of the ionosphere, especially for high latitudes and during ionospheric disturbances.
Open Access
Regularized estimation of vertical total electron content from GPS data for a desired time period
(Wiley-Blackwell, 2004) Arikan, F.; Erol, C. B.; Arıkan, Orhan
In this paper a new algorithm for short-term regularized estimation of vertical total electron content (VTEC) from Global Positioning System (GPS) data is developed. The regularization technique can combine signals, from all GPS satellites for a given instant and a given receiver, for a desired time duration within the 24 hour period without missing any important features in the temporal domain. The algorithm is based on the minimization of a cost function which includes a high pass penalty filter and detrend processing. With an optional weighting function the multipath effects are reduced. A final sliding window median filter is added to enrich the processing and smoothing of the data. The developed regularized estimation algorithm is applied to GPS data for various locations for the solar maximum week of 23-28 April 2001. The parameter set that is required by the estimation algorithm is chosen optimally using appropriate error functions. For this data set the chosen robust and optimum parameters can be used for all latitudes and for both quiet and disturbed days for a minimum of one hour time period. It is observed that the estimated TEC values are in very accordance with the TEC estimates for the 24 hour period. Owing to its 30 s time resolution, the regularized VTEC estimates from the developed algorithm are very successful in representation and tracking of sudden temporal variations of the ionosphere, especially for high latitudes and during ionospheric disturbances.
Open Access
Space weather activities of IONOLAB group using TNPGN GPS Network
(IEEE, 2011) Aktug, B.; Lenk O.; Kurt, M.; Parmaksiz, E.; Ozdemir, S.; Arikan F.; Sezen, U.; Toker, C.; Arıkan, Orhan
Characterization and constant monitoring of variability of the ionosphere is of utmost importance for the performance improvement of HF communication, Satellite communication, navigation and guidance systems, Low Earth Orbit (LEO) satellite systems, Space Craft exit and entry into the atmosphere and space weather. Turkish National Permanent GPS Network (TNPGN) is the Reference Station Network of 146 continuously-operating GNSS stations of which are distributed uniformly across Turkey and North Cyprus Turkish Republic since May 2009. IONOLAB group is currently investigating new techniques for space-time interpolation, and automatic mapping of TEC through a TUBITAK research grant. It is utmost importance to develop regional stochastic models for correction of ionospheric delay in geodetic systems and also form a scientific basis for communication link characterization. This study is a brief summary of the efforts of IONOLAB group in monitoring of space weather, and correction of geodetic positioning errors due to ionosphere using TNPGN. © 2011 IEEE.
Open Access
Space weather studies of IONOLAB group
(IEEE, 2016) Arıkan, F.; Sezen, U.; Toker, C.; Artuner, H.; Bulu, G.; Demir, U.; Erdem, E.; Arıkan, Orhan; Tuna, Hakan; Gulyaeva, T. L.; Karatay, S.; Mosna, Z.
IONOLAB is an interdisciplinary research group dedicated for handling the challenges of near earth environment on communication, positioning and remote sensing systems. IONOLAB group contributes to the space weather studies by developing state-of-the-art analysis and imaging techniques. On the website of IONOLAB group, www.ionolab.org, four unique space weather services, namely, IONOLAB-TEC, IRI-PLAS-2015, IRI-PLAS-MAP and IRI-PLAS-STEC, are provided in a user friendly graphical interface unit. Newly developed algorithm for ionospheric tomography, IONOLAB-CIT, provides not only 3-D electron density but also tracking of ionospheric state with high reliability and fidelity. The algorithm for ray tracing through ionosphere, IONOLAB-RAY, provides a simulation environment in all communication bands. The background ionosphere is generated in voxels where IRI-Plas electron density is used to obtain refractive index. One unique feature is the possible update of ionospheric state by insertion of Total Electron Content (TEC) values into IRI-Plas. Both ordinary and extraordinary paths can be traced with high ray and low ray scenarios for any desired date, time and transmitter location. 2-D regional interpolation and mapping algorithm, IONOLAB-MAP, is another tool of IONOLAB group where automatic TEC maps with Kriging algorithm are generated from GPS network with high spatio-temporal resolution. IONOLAB group continues its studies in all aspects of ionospheric and plasmaspheric signal propagation, imaging and mapping.