UNB Scholar Research Repository :: Browsing by Author "Delikaraoglou, Demitris"

Browsing by Author "Delikaraoglou, Demitris"

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Application of NAVSTAR/GPS to geodesy in Canada: Pilot Study
Wells, David; Vanĩcek, Peter; Delikaraoglou, Demitris
Application of NAVSTAR/GPS to geodesy in Canada: Pilot Study
Wells, David; Vanĩcek, Peter; Delikaraoglou, Demitris
Global Positioning System differential positioning simulations
Davidson, Derek; Delikaraoglou, Demitris; Langley, Richard; Nickerson, Bradford; Vanicek, Petr; Wells, David
Global Positioning System differential positioning simulations
Davidson, Derek; Delikaraoglou, Demitris; Langley, Richard; Nickerson, Bradford; Vanicek, Petr; Wells, David
NAVSTAR performance analysis
Wells, David; Delikaraoglou, Demitris
The two dimensional, real time navigational accuracy available from NAVSTAR/GPS is investigated, with emphasis on GPS performance during the partially implemented phase (1980 to 1987), and on the ocean areas surrounding Canada. The mathematical models used in this study to compute NAVSTAR satellite positions, check for satellite visibility, and compute the covariance matric of two dimensional position are described. The length of the semi major axis of the standard error ellipse represented by this covariance matrix is used as the GPS performance indicator. A computer program implementing these models is listed. Results based on four error models are presented. These error models are P-code ranging only (with 4 metre tang errors), C/A-code ranging only (16 metre range errors), P-code assisted by Loran-C and C/A-code assisted by Loran-C. For this analysis Loran-C range to Cape Race, Angissoq and Sandur were assumed to have standard deviations of 140 m. In all cases it was assumed that the user’s clock could be kept synchronized to GPS time independently from the GPS measurements, to within 0.3 microseconds. Based on these assumptions, it was found that in the Davis Strait area, combined P-code GPS and Loran-C should provide 150 metre positioning about 11 hours per day, with the present (1980) orbital configuration of six GPS satellites. GPS performance with only six satellites is also a function of both latitude and longitude. In general high latitude (60 ° and above) have poorer performance. The performance at low and middle latitude depends on the relationship between the observer’s meridian and the meridians travelled by the GPS satellite subtracks. Plots of the variation in the length of the GPS error ellipse semi major axis over a 24 hours period are presented for 14 different locations. Compete output listings are presented for three locations and several error models. A full GPS constellation of 24 satellites was simulated. The two dimensional, P-code positioning accuracy in Davis Strait, using all visible satellites was uniformly of the order of five metres. It is concluded that it is feasibly to use GPS in its present limited deployment as an operational survey positioning systems in the eastern Canadian artic, provided the requirements of the survey are met by 150 metres or better positioning for about 11 hours a day.
NAVSTAR performance analysis
Wells, David; Delikaraoglou, Demitris
The two dimensional, real time navigational accuracy available from NAVSTAR/GPS is investigated, with emphasis on GPS performance during the partially implemented phase (1980 to 1987), and on the ocean areas surrounding Canada. The mathematical models used in this study to compute NAVSTAR satellite positions, check for satellite visibility, and compute the covariance matric of two dimensional position are described. The length of the semi major axis of the standard error ellipse represented by this covariance matrix is used as the GPS performance indicator. A computer program implementing these models is listed. Results based on four error models are presented. These error models are P-code ranging only (with 4 metre tang errors), C/A-code ranging only (16 metre range errors), P-code assisted by Loran-C and C/A-code assisted by Loran-C. For this analysis Loran-C range to Cape Race, Angissoq and Sandur were assumed to have standard deviations of 140 m. In all cases it was assumed that the user’s clock could be kept synchronized to GPS time independently from the GPS measurements, to within 0.3 microseconds. Based on these assumptions, it was found that in the Davis Strait area, combined P-code GPS and Loran-C should provide 150 metre positioning about 11 hours per day, with the present (1980) orbital configuration of six GPS satellites. GPS performance with only six satellites is also a function of both latitude and longitude. In general high latitude (60 ° and above) have poorer performance. The performance at low and middle latitude depends on the relationship between the observer’s meridian and the meridians travelled by the GPS satellite subtracks. Plots of the variation in the length of the GPS error ellipse semi major axis over a 24 hours period are presented for 14 different locations. Compete output listings are presented for three locations and several error models. A full GPS constellation of 24 satellites was simulated. The two dimensional, P-code positioning accuracy in Davis Strait, using all visible satellites was uniformly of the order of five metres. It is concluded that it is feasibly to use GPS in its present limited deployment as an operational survey positioning systems in the eastern Canadian artic, provided the requirements of the survey are met by 150 metres or better positioning for about 11 hours a day.
Sea surface computations from local satellite tracking and satellite altimetry
Delikaraoglou, Demitris
The user of satellite radar altimetry in acquiring geodetic data over oceanic areas is investigated using precise ephemeris information for satellite coordinates and GEOS-3 altimetry data collected within the context of a Canadian GEOS-3 altimetry experiment conducted in the Hudson Bay area. GEOS-3 Doppler tracking data from four stations in the vicinity of Hudson Bay are analysed for the purpose of establishing the extent of local improvement of the orbits required to reduce the altimetry data. The a priori decisions involved in the computation of mean sea surface were to use precise ephemeris information; to use the available Doppler tracking data to reduce the ephemeris errors by means of the semi short-arc technique in the translocation mode; to use these Doppler fitted orbits to reduce and adjust the altimetry data; and to compare the results to various versions of the geoid to establish the degree of usefulness of the satellite altimetry technique for the determination of the sea surface topography. The estimation of sea surface from satellite altimetry data is discussed. The problem areas and the various sources of errors inherent in the satellite altimetry observables used to define the sea surface are identified and their respective modelling with the context of this study is examined in detail. The basic principles of the semi short-arc method, conventionally used in Canada for geodetic positioning, are related here to the intended local improvement of the orbits required to utilize the altimetry data. From numerical results based on the combination of the available GEOS-3 Doppler data with reference orbits described in this case by a set of DMA precise ephemerides, precise ephemeris errors exceeding occasionally 10 m int he radial direction were found. The formulation of the least squares model of intersecting altimetry arcs are used here to remove long wavelength errors primarily due to unmodelled gravity field effects in the orbit determination is examined in detail. Residual orbit biases are found to be well represented by an absolute bias and a tilt parameter for each arc. From the study of a regional network of GEOS-3 orbital arcs in Hudson Bay the internal consistency of the estimated sea surface is found to be less than one metre, whereas the rms difference of the sea surface heights at the intersection points is found to be 1.1 m. Comparisons of the altimetry-derived sea surface with a GEOS-3 sea surface independently determine by DMA indicated a relative consistency of 0;98 m (rms), attributed primarily to the presence of unmodelled time varying effects in the sea surface and anticipated differences induced by the difference reduction procedures used to obtain the adjusted altimetry data. Comparisons with two combined geoids indicated an agreement of the order of 1.2 m (rms), attributed mainly to errors in the computed geoids and some level of spurius structure possibly introduced into the sea surface because of the Doppler orbit adjustment. Based on the analysis and the results of this study, several contributions relevant to the problem of acquiring geodetic data in oceanic areas form satellite altimetry have resulted from this research. Of these, the following are considered, int he authors opinion to be the most significant: 1. The practical demonstration of the feasibility of improvement of the orbits required to utilize the altimetry data from local satellite tracking; the implications from the present results are that if local Doppler tracking can improve orbital information as good as the precise ephemeris, it should be even more important in the case of worse available reference orbits. 2. A complete discussion into the diverse kinds of information which needs to be considered in any attempt of utilizing satellite altimetry data. While the results presented herein are based on assumptions and decision pertaining to the intended application of the Hudson Bay Experiment, the information contained in this thesis should serve to highlight the strengths and the weaknesses of the estimation process used in this study hence usefully direct further investigations towards future applications. 3. The development of a complete computer package of the programs (available at the Department of Surveying Engineering at UNB) designed to combine information similar to the one used in this study.
Sea surface computations from local satellite tracking and satellite altimetry
Delikaraoglou, Demitris
The user of satellite radar altimetry in acquiring geodetic data over oceanic areas is investigated using precise ephemeris information for satellite coordinates and GEOS-3 altimetry data collected within the context of a Canadian GEOS-3 altimetry experiment conducted in the Hudson Bay area. GEOS-3 Doppler tracking data from four stations in the vicinity of Hudson Bay are analysed for the purpose of establishing the extent of local improvement of the orbits required to reduce the altimetry data. The a priori decisions involved in the computation of mean sea surface were to use precise ephemeris information; to use the available Doppler tracking data to reduce the ephemeris errors by means of the semi short-arc technique in the translocation mode; to use these Doppler fitted orbits to reduce and adjust the altimetry data; and to compare the results to various versions of the geoid to establish the degree of usefulness of the satellite altimetry technique for the determination of the sea surface topography. The estimation of sea surface from satellite altimetry data is discussed. The problem areas and the various sources of errors inherent in the satellite altimetry observables used to define the sea surface are identified and their respective modelling with the context of this study is examined in detail. The basic principles of the semi short-arc method, conventionally used in Canada for geodetic positioning, are related here to the intended local improvement of the orbits required to utilize the altimetry data. From numerical results based on the combination of the available GEOS-3 Doppler data with reference orbits described in this case by a set of DMA precise ephemerides, precise ephemeris errors exceeding occasionally 10 m int he radial direction were found. The formulation of the least squares model of intersecting altimetry arcs are used here to remove long wavelength errors primarily due to unmodelled gravity field effects in the orbit determination is examined in detail. Residual orbit biases are found to be well represented by an absolute bias and a tilt parameter for each arc. From the study of a regional network of GEOS-3 orbital arcs in Hudson Bay the internal consistency of the estimated sea surface is found to be less than one metre, whereas the rms difference of the sea surface heights at the intersection points is found to be 1.1 m. Comparisons of the altimetry-derived sea surface with a GEOS-3 sea surface independently determine by DMA indicated a relative consistency of 0;98 m (rms), attributed primarily to the presence of unmodelled time varying effects in the sea surface and anticipated differences induced by the difference reduction procedures used to obtain the adjusted altimetry data. Comparisons with two combined geoids indicated an agreement of the order of 1.2 m (rms), attributed mainly to errors in the computed geoids and some level of spurius structure possibly introduced into the sea surface because of the Doppler orbit adjustment. Based on the analysis and the results of this study, several contributions relevant to the problem of acquiring geodetic data in oceanic areas form satellite altimetry have resulted from this research. Of these, the following are considered, int he authors opinion to be the most significant: 1. The practical demonstration of the feasibility of improvement of the orbits required to utilize the altimetry data from local satellite tracking; the implications from the present results are that if local Doppler tracking can improve orbital information as good as the precise ephemeris, it should be even more important in the case of worse available reference orbits. 2. A complete discussion into the diverse kinds of information which needs to be considered in any attempt of utilizing satellite altimetry data. While the results presented herein are based on assumptions and decision pertaining to the intended application of the Hudson Bay Experiment, the information contained in this thesis should serve to highlight the strengths and the weaknesses of the estimation process used in this study hence usefully direct further investigations towards future applications. 3. The development of a complete computer package of the programs (available at the Department of Surveying Engineering at UNB) designed to combine information similar to the one used in this study.
Studies in the application of the Global Positioning System to differential positioning
Langley, Richard, B.; Beutler, Gerhard; Delikaraoglou, Demitris; Nickerson, Bradford, G; Santerre, Rock; Vanĩcek, Petr; Weels, David, E.
Studies in the application of the Global Positioning System to differential positioning
Langley, Richard, B.; Beutler, Gerhard; Delikaraoglou, Demitris; Nickerson, Bradford, G; Santerre, Rock; Vanĩcek, Petr; Weels, David, E.

Browsing by Author "Delikaraoglou, Demitris"

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