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Open access

Aleksander Nowak

Abstract

The European Geostationary Navigation Overlay Service (EGNOS) thanks to geostationary satellites covers an area of whole Europe, including Baltic and North Sea. It allows to fix the coordinates of object position with typical absolute accuracy of 1,5 m. Previous research have shown that relative accuracy is usually higher than absolute one [Nowak A., 2010; Nowak A., 2011], so probably it could be possible to use EGNOS to determine direction in space. The research described in the paper concerned relative accuracy of three homogeneous EGNOS receivers, in context of the ability to determine the ship’s hull spatial orientation. Theoretical basis, the process of the experiment and the results of recorded data analysis were described. The research were conducted in the summer of 2014. Three homogenous Leica Viva series receivers were used. They were configured to receive a differential messages of the EGNOS system. Recorded data were analyzed in context of fixes relative accuracy. On the basis of achieved results, a conclusion about the possibility of construction the measurement system for the automatic determination of the ship’s hull spatial orientation angles in real time was drawn. The further research directions were pointed out, too.

Open access

Aleksander Nowak

Abstract

Nowadays, we can observe an increase in research on the use of small unmanned autonomous vessel (SUAV) to patrol and guiding critical areas including harbours. The proposal to “snapshot” RAIM (Receiver Autonomous Integrity Monitoring) method for GNSS receivers mounted on SUAV operating in poor space segment geometry is presented in the paper. Existing “snapshot” RAIM methods and algorithms which are used in practical applications have been developed for airborne receivers, thus two main assumptions have been made. The first one is that the geometry of visible satellites is strong. It means that the exclusion of any satellite from the positioning solution don’t cause significant deterioration of Dilution of Precision (DOP) coefficients. The second one is that only one outlier could appear in pseudorange measurements. In case of SUAV operating in harbour these two assumptions cannot be accepted. Because of their small dimensions, GNSS antenna is only a few decimetres above sea level and regular ships, buildings and harbour facilities block and reflect satellite signals. Thus, different approach to “snapshot” RAIM is necessary. The proposal to method based on analyses of allowable maximal separation of positioning sub-solutions with using some information from EGNOS messages is described in the paper. Theoretical assumptions and results of numerical experiments are presented.

Open access

Andrzej Felski and Aleksander Nowak

Abstract

Any SBAS system, as soon as it is permanently monitored by Earth stations, should deliver to the users correct information about quality of the augmented system. According to many sources of information, among them observations of authors, present accuracy of EGNOS service has accuracy about 1,5m (95%), but availability of the service is still controversial. First of all the quality of the system is guaranteed only inside the border of the system coverage which still do not affect all territory of European Union, however observed accuracy at times is better outside this area than next door to the RIMS station. In addition there are evidences that availability has random character and essential differences as well as lack of correlation of this parameter in the different point of observations has been observed. So in author’s opinion Local Monitoring of EGNOS service can contribute to better confidence of local users, especially in critical operations, like for example berthing of big ships or landing operations with EGNOS procedures. The example of EGNOS monitor which is working in real time and performed by the authors will be presented

Open access

Andrzej Felski, Aleksander Nowak and Tomasz Woźniak

Accuracy and Availability of Egnos - Results of Observations

According to SBAS concept the user should receive timely the correct information about the system integrity and corrections to the pseudoranges measurements, which leads to better accuracy of coordinates. In theory the whole system is permanently monitored by RIMS stations, so it is impossible to deliver the faulty information to the user. The quality of the system is guaranteed inside the border of the system coverage however in the east part of Poland lower accuracy and availability of the system is still observed. This was the impulse to start an observation and analysis of real accuracy and availability of EGNOS service in the context of support air-operations in local airports and as the supplementation in hydrographic operations on the Polish Exclusive Zone.

A registration has been conducted on three PANSA stations situated on airports in Warsaw, Krakow and Rzeszow and on PNA station in Gdynia. Measurements on PANSA stations have been completed permanently during each whole month up to end of September 2011. These stations are established on Septentrio PolaRx2e receivers and have been engaged into EGNOS Data Collection Network performed by EUROCONTROL. The advantage of these registrations is the uniformity of receivers. Apart from these registrations additional measurements in Gdynia have been provided with different receivers, mainly dedicated sea-navigation: CSI Wireless 1, NOVATEL OEMV, Sperry Navistar, Crescent V-100 and R110 as well as Magellan FX420.

The main object of analyses was the accuracy and availability of EGNOS service in each point and for different receivers. Accuracy has been analyzed separately for each coordinate. Finally the temporarily and spatial correlations of coordinates, its availability and accuracy has been investigated.

The findings prove that present accuracy of EGNOS service is about 1,5m (95%), but availability of the service is controversial. The accuracy of present EGNOS service meets the parameters of APV I and even APV II requirements, as well as any maritime and hydrography needs. However introducing this service into the practice demands better availability, because the gaps in receiving the proper information from the system appear too often and are too long at the moment. Additionally it was noticed very random character of availability and no correlation of this parameter in the different point of observations. In spite the correct EGNOS work the accuracy of the coordinates is not predictable in the local conditions. So in authors' opinion Local Airport Monitoring should be deployed if EGNOS would have to serve to the local airport service.

Open access

Andrzej Felski and Aleksander Nowak

ABSTRACT

Any SBAS system should deliver to the user corrections to pseudoranges as well as information about the system integrity. In theory, as soon as the system is permanently monitored by RIMS stations, it is impossible to deliver the fault information to the user. However many observations shows that accuracy of EGNOS service in the same time are different in different places, which shows the influence of local conditions on them. In addition evidences on possibilities in jamming or spoofing of GPS signals should be seriously taken into account. According to many sources of information, among them observations of authors, present accuracy of EGNOS service has better than declared. In fact EGNOS accuracy is about 1,5m (95%), but availability of the service happens still controversial and it has random character. According to reports essential differences as well as lack of correlation of this parameter in the different point of observations has been observed. So in author’s opinion Local Monitoring of EGNOS service can contribute to better confidence of local users, especially in critical operations, like for example berthing of big ships or in landing operations with EGNOS procedures. An example of such system which works in real time has been elaborated in Polish Naval Academy and will be presented.

Open access

Marcin Barczyński, Aleksander Konturek, Małgorzata Stopa, Filip Gołkowski, Alicja Hubalewska-Dydejczyk, Stanisław Cichoń and Wojciech Nowak

Bilateral Neck Exploration with Intraoperative iPTH Assay in the ERA of Minimaly Invasive Parathyroidectomy

At present, the majority of patients with sporadic primary hyperparathyroidism (pHPT) qualify to minimally invasive parathyroidectomy (MIP). Nevertheless, in some patients, especially those with multiglandular parathyroid disease, achieving normocalcemia necessitates bilateral neck exploration (BNE).

The aim of the study was evaluation of current indications for BNE and results obtained employing this method in an endocrine surgery referral center.

Material and methods. A prospective analysis included 385 patients with pHPT qualified to parathyroidectomy (300 to MIP and 85 to BNE procedures) in the period between 12/2002 and 05/2008. Prior to the procedure, all the patients underwent preoperative imaging diagnostic studies (scintiscans of the parathyroids and ultrasound of the neck). Intraoperative parathormone assay was carried out in the course of all the operations. Indications for BNE and therapeutic results were evaluated.

Results. The most common indication for BNE was lack of preoperative location of a parathyroid adenoma in imaging studies aiming either at lateralization or regionalization (49.4%), followed by concomitant thyroid pathology that required surgical treatment (23.5%), MEN 1 syndrome (12.9%), long-term lithium therapy (5.9%), refusal of the patient to grant informed consent to a minimally invasive parathyroidectomy (5.9%) and MEN 2A syndrome (2.4%). In the discussed group, 31 subtotal parathyroidectomies were performed, along with ten resections of two parathyroid adenomas and 44 resections of single parathyroid adenomas. Intraoperative iPTH assay affected the extent of parathyroid tissues resection in eight (9.4%) cases. One case of persistent and one case of recurrent hyperparathyroidism were noted in the follow-up of mean 37.4 ± 19.4 months postoperatively.

Conclusions. In an endocrine surgery referral center, BNE is a procedure of choice in patients suspected of multiglandular parathyroid disease (MEN 1 and 2A, familial pHPT, long-term lithium therapy), in cases when a pathological parathyroid has not been located preoperatively and in patients which refuse their consent to MIP. Supplementing BNE with intraoperative iPTH assay allows for maintaining the highest quality of surgical treatment.

Open access

Marcin Barczyński, Aleksander Konturek, Małgorzata Stopa, Alicja Hubalewska-Dydejczyk, Piotr Richter and Wojciech Nowak

Clinical Value of Intraoperative Neuromonitoring of the Recurrent Laryngeal Nerves in Improving Outcomes of Surgery for Well-Differentiated Thyroid Cancer

The recurrent laryngeal nerve (RLN) is particularly prone to injury during thyroidectomy in case of extralaryngeal bifurcation being present in approximately one-third of patients near the inferior thyroid artery or ligament of Berry. Meticulous surgical dissection in this area may be additionally facilitated by the use of intraoperative neuromonitoring (IONM) to assure safe and complete removal of thyroid tissue.

The aim of the study was to verify the hypothesis that meticulous surgical technique of tissue dissection in the area of the posterior surface of the thyroid capsule and adjacent RLN may be additionally facilitated by intraoperative neuromonitoring (IONM), and may contribute to increasing the safety and radicalness of total thyroidectomy in patients with well-differentiated thyroid cancer.

Material and methods. The outcomes of total thyroidectomy with level VI lymph node clearance for well-differentiated thyroid cancer (WDTC; pT1-3, N0-1, Mx) were retrospectively compared between 151 patients undergoing surgery with IONM (01/2005-06/2009) and 151 patients undergoing surgery without IONM (2003-2004). RLN morbidity (calculated for nerves at risk) was assessed by videolaryngoscopy or indirect laryngoscopy (mandatory before and after surgery and at 12-month follow-up). The anatomical course of the extralaryngeal segment of RLNs were analyzed in detail in each operation. Thyroid iodine uptake (131I) was measured during endogenous TSH stimulation test a week before radioiodine therapy.

Results. Among patients operated with vs. without IONM, the early RLN injury rate was 3% vs. 6.7% (p=0.02), including 2% vs. 5% (p=0.04) of temporary nerve lesions, and 1% vs. 1.7% of permanent nerve events (p=0.31), respectively. Extralaryngeal RLN bifurcation was identified in 42 (27.8%) vs. 25 (16.6%) of patients operated with vs. without IONM, respectively (p=0.001). Mean I-131 uptake following total thyroidectomy with vs. without IONM was 0.67 ± 0.39% vs. 1.59 ± 0.69% (p<0.001). 131I uptake lower than 1% was found in 106 (70.2%) vs. 38 (25.2%) patients operated with vs. without IONM, respectively (p<0.001).

Conclusions. Most patients with WDTC who undergo total thyroidectomy have a small amount of residual thyroid tissue. The use of IONM may improve the outcomes of surgery among these patients by both increasing the completeness of total thyroidectomy and significantly reducing the prevalence of temporary RLN injury. The possible mechanism of this improvement is the aid in dissection at the level of the Berry's ligament offered by IONM which enhances the surgeon's ability to identify a branched RLN, and allows for reduction of traction injury and neuropraxia of the anterior branch of bifid nerves.

Open access

Andrzej Cichowski, Marek Kawecki, Justyna Glik, Agnieszka Klama-Baryła, Wojciech Łabuś, Mariusz Maj, Mariusz Nowak, Andrzej Dworak and Aleksander L. Sieroń