Browsing by Author "Mtamakaya, James, D."
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Item Assessment of atmospheric pressure loading on the international GNSS REPRO1 solutions periodic signaturesMtamakaya, James, D.Unambiguous, consistent and homogeneous GPS station coordinates are the fundamental requirement in the appropriate determination of geodetic velocities that are often used to derive geodetic and geophysical models for different applications. As for that, there have been significant efforts in the past decade to improve the modeling and parameterization of GPS solutions. Recently, the International GNSS Service (IGNSS) has generated REPRO1 solutions by reprocessing the historical GPS data from 1994 to March, 2010. REPRO1 solutions adopted the new absolute antenna phase center variations models along with most of the recent model parameters available by then and they are the first solutions to be consistently represented in one reference frame, IGS05. Based on the availability of REPRO1 solutions, this research has two objectives. The primary objective is to identify the remaining periodic signatures in the International GNSS REPRO1 solutions. These signatures are the impacts of short and long term mismodeled and unmodeled effects from both known and unknown phenomena. As a parallel activity, this research will try to explain the signatures by correlating them with different effects that have either not been modeled or modeled differently with a specific attention to the atmospheric pressure loading (APL). The secondary objective of this study is to perform the harmonic analysis investigation of weekly time series in position and residual domain of REPRO1 solution using Least Squares Spectral Analysis (LSSA) and Least Squares Coherent Analysis (LSCA) with and without APL corrections. Based on the resulting least squares spectra, the impact (benefits) of APL corrections in the present solutions have been assessed as a basis of formulating recommendations in future similar reprocessing campaigns. In order to accomplish the research objectives, a set of twenty nine (29) stations (part of the present IGNSS network) were selected in a manner which would portray the global overview. Thereafter, the selected stations analyzed using Least Squares Spectral Analysis (LSSA) and Least Squares Coherent Analysis (LSCA) frequency domain multiplications with and without the impact of APL from GGFC model. The investigations were carried out at both REPRO1 positions and residuals domains. Based on the LS spectra results, it is evident that periodic signatures are still present in the REPRO1 solutions for most of the stations under study and they appear as spectral peaks. Furthermore, the observed signatures appear to be consistent around the first to fourth draconitic harmonics with respective periods of 351.2, 175.6, 117.1 and 87.8 days, within a range of ± 14 days (±0.04 CPY). It was also observed that, there is a slight improvement to spectral peaks that may result into slight improvement of coordinate repeatability if APL were included in the processing. However, the pattern was neither clear nor consistent at different harmonic levels of the same station as well as from one station to another. Furthermore, it was also observed that, the APL does not cause any significant reduction in spectral peaks that are still present in the REPRO1 solutions. This suggest that most of the remaining signatures could be attributed to other un-modeled displacements such as non tidal loading displacement, high order ionosphere terms and mismodeling effect in GPS attitude models. To ascertain the findings, independent solutions for YELL and NRC1 were generated (1995-2010) using Bernese v5.0 software in a baseline mode, in conjunction with latest IERS models. The computed solutions were verified to be compatible with present solutions within a range of ±2.5 cm. Thereafter the computed solutions were analyzed with and without the impact of APL using LSSA and LSCA as a basis of recommendations and future work.Item Establishment and maintenance of a new geospatial frame for Tanzania-TZRF10Mtamakaya, James, D.Tanzania like most of the African countries has an old and conventional Geodetic Network. This network was established and computed by the Directorate of Overseas Surveys (DOS) of Great Britain in the 1950’s. The present network is based on the 30th arc-meridian of the Clarke 1880 modified ellipsoid with its origin at Buffelsfontein-Cape Town in the Republic of South Africa. The present network does not satisfy the overgrowing mapping requirements of the country as well as other Geo-related information requirements. They include homogeneous cross border mapping activities (most of the international boundaries have not been physically defined), smooth land regularization projects in new urban areas, production and update of large scale topographical maps in urban areas and homogenous spatial mapping as well as the studies of crustal dynamics as related to plate tectonics and natural hazards associated with seismic or volcanic activities. The Survey and Mapping Division of Tanzania (SMD) has realized the values of high precision and geocentric dynamic spatial frame in facilitating the geodetic positioning (coordinates and velocities in the geocentric coordinate system), navigation and general purpose spatial referencing to date as the most versatile, accurate and economical way of addressing the above issues. In view of those values and strong capabilities of modern dynamic geodetic frames, Tanzania has been collaborating with other African countries to establish a unified African Geodetic Reference Frame (AFREF). However, lack of appropriate expertise, proper awareness of the concept amongst most of the national mapping organizations and differences in economic levels in the African countries have always been the limiting factors. In view those limitations, the primary objective of this thesis is to provide the basis for the establishment and maintenance of a 3-dimensional dynamic reference frame for Tanzania in the ITRF system with optimum accuracy requirement in an economic way. The new frame will be compatible to satellite position techniques and would consider the advancement in the communication technology and the increased capacity of the internet applications real time geodetic applications that has been illustrated by Weber [2002] and Weber et al. [2003]. To achieve the research objectives a conceptual plan to realize a new spatial framework in Tanzania (TZRF10) has been developed, using the least-squares covariance analysis technique as a tool to evaluate for its geometrical consistency. A case study on reference frame maintenance using the BerneseV5.0 scientific software; has been developed and evaluated for its performance based on NAD83 (CSRS) data from the Geodetic Survey Division of Natural Resources of Canada NRCan. The present advancement in communication technologies and increased capacity of internet–based real time geodetic applications has been illustrated through implementation of a case study and evaluated for its performance using a developed matlab software code.Item Establishment and maintenance of a new geospatial frame for Tanzania-TZRF10Mtamakaya, James, D.Tanzania like most of the African countries has an old and conventional Geodetic Network. This network was established and computed by the Directorate of Overseas Surveys (DOS) of Great Britain in the 1950’s. The present network is based on the 30th arc-meridian of the Clarke 1880 modified ellipsoid with its origin at Buffelsfontein-Cape Town in the Republic of South Africa. The present network does not satisfy the overgrowing mapping requirements of the country as well as other Geo-related information requirements. They include homogeneous cross border mapping activities (most of the international boundaries have not been physically defined), smooth land regularization projects in new urban areas, production and update of large scale topographical maps in urban areas and homogenous spatial mapping as well as the studies of crustal dynamics as related to plate tectonics and natural hazards associated with seismic or volcanic activities. The Survey and Mapping Division of Tanzania (SMD) has realized the values of high precision and geocentric dynamic spatial frame in facilitating the geodetic positioning (coordinates and velocities in the geocentric coordinate system), navigation and general purpose spatial referencing to date as the most versatile, accurate and economical way of addressing the above issues. In view of those values and strong capabilities of modern dynamic geodetic frames, Tanzania has been collaborating with other African countries to establish a unified African Geodetic Reference Frame (AFREF). However, lack of appropriate expertise, proper awareness of the concept amongst most of the national mapping organizations and differences in economic levels in the African countries have always been the limiting factors. In view those limitations, the primary objective of this thesis is to provide the basis for the establishment and maintenance of a 3-dimensional dynamic reference frame for Tanzania in the ITRF system with optimum accuracy requirement in an economic way. The new frame will be compatible to satellite position techniques and would consider the advancement in the communication technology and the increased capacity of the internet applications real time geodetic applications that has been illustrated by Weber [2002] and Weber et al. [2003]. To achieve the research objectives a conceptual plan to realize a new spatial framework in Tanzania (TZRF10) has been developed, using the least-squares covariance analysis technique as a tool to evaluate for its geometrical consistency. A case study on reference frame maintenance using the BerneseV5.0 scientific software; has been developed and evaluated for its performance based on NAD83 (CSRS) data from the Geodetic Survey Division of Natural Resources of Canada NRCan. The present advancement in communication technologies and increased capacity of internet–based real time geodetic applications has been illustrated through implementation of a case study and evaluated for its performance using a developed matlab software code.