Detecção e correção de perdas de ciclos para dados GPS de tripla frequência
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Data
2019-04-26
Autores
Mendonça, Caio Henrique Chrisóstomo [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A observável fase da onda portadora é utilizada quando se deseja obter alta acurácia no posicionamento por sistemas globais de navegação por satélite. Mas, esta observável pode sofrer perdas de ciclos durante o rastreamento do sinal. Uma perda de ciclo é uma descontinuidade de um número inteiro de ciclos na fase da onda portadora, causada por uma perda temporária de rastreamento do sinal pelo receptor. Assim, as perdas de ciclos devem ser detectadas e corrigidas para que se obtenha posicionamento acurado. Diversos métodos foram desenvolvidos com esse objetivo. Algo que também vem sendo amplamente estudado é a detecção das perdas de ciclos nos novos sinais GPS. O advento da terceira frequência disponibilizada a partir da modernização do GPS também deve ser explorado. Na presente pesquisa buscou-se estudar os diferentes métodos de detecção e correção de perdas de ciclos e implementar o mais adequado para o posicionamento de alta acurácia no Brasil. Foram selecionadas duas metodologias para fim de detecção e correção, sendo a primeira baseada no método das triplas diferenças (TD) clássico e a segunda baseada no método de sequência de combinações lineares. Além disso, foi proposta uma terceira metodologia para melhoria do método das TD. Foram realizados dois experimentos, sendo o primeiro realizado com dados simulados e o segundo com dados reais em período de alta atividade ionosférica, e para ambos os casos foram considerados dois cenários: linha de base curta e linha de base longa. Para dados simulados, em linha de base curta, o método TD clássico, o método TD proposto e o método das sequências de combinações lineares apresentaram 100%, 99,91% e 100% de acerto na detecção, resultando em 99,91%, 99,88% e 100% de acerto na correção das perdas de ciclos, respectivamente. Para linha de base longa, com dados simulados, obteve-se 31,37%, 63,79% e 100% de acerto na detecção, resultando em 49,45%, 95,32% e 100% de acerto na correção das perdas de ciclos quando utilizado o método TD clássico, o método TD proposto e o método das sequências de combinações lineares, respectivamente. No segundo experimento, conduzido com dados reais foi possível avaliar somente a melhoria no posicionamento, sendo esta para linha de base curta, de 81,71%, 67,08% e 10,79% para o método TD clássico, o método TD proposto e o método das sequências de combinações lineares, respectivamente. Em linha de base longa, após correção, o método TD clássico obteve piora de 12,18%, o método TD proposto proporcionou melhoria de 40,63%, enquanto o método das combinações lineares não apresentou melhoria.
Carrier phase observable are used in high accuracy positioning by global navigation satellite systems. However, the carrier phase measurement may suffer cycle slips during signal tracking. A cycle slip is a discontinuity of an integer number of cycles in the phase observable, caused by a temporary loss of lock in the receiver carrier tracking loop. Thus, cycle slips must be detected and corrected in order to obtain accurate positioning. Several methods were developed for this purpose. Something that has also been studied is the detection of cycle slip in the new GPS signals. The advent of the third frequency available from the GPS modernization. Should be explored in the context of cycle slip detection and correction. In the present research the different cycle slip detection and correction methods were studied and t the most suitable for the high accuracy positioning in Brazil was implemented. Two methodologies were selected for the purpose of this research, the first one based on the classical triple difference (TD) method and the second based on the linear combination sequence method. In addition, a third methodology was proposed to improve the TD method. Two experiments were performed, the first one being carried out with simulated data and the second with real data in the period of high ionospheric activity, and for both cases two scenarios were considered: short baseline and long baseline. For simulated short baseline data, the classical TD method, the proposed TD method and the linear combination sequence method presented 100%, 99.91% and 100% accuracy in the detection, resulting in 99.91%, 99.88% and 100% accuracy in the correction of cycle slips, respectively. For the simulated long baseline data, 31.37%, 63.79% and 100% of detection accuracy were obtained, resulting in 49.45%, 95.32% and 100% accuracy in the correction of cycles slips when using the classical TD method, the proposed TD method and the linear combination sequence method, respectively. In the second experiment, conducted with real data, it was possible to evaluate only the improvement in the positioning, being this for short baseline, of 81.71%, 67.08% and 10.79% for the classical TD method, the proposed TD method and linear combination sequence method, respectively. In the long baseline, after correction, the classical TD method obtained a worsening of 12.18%, the proposed TD method provided an improvement of 40.63%, whereas the linear combination sequence method could not show evaluated.
Carrier phase observable are used in high accuracy positioning by global navigation satellite systems. However, the carrier phase measurement may suffer cycle slips during signal tracking. A cycle slip is a discontinuity of an integer number of cycles in the phase observable, caused by a temporary loss of lock in the receiver carrier tracking loop. Thus, cycle slips must be detected and corrected in order to obtain accurate positioning. Several methods were developed for this purpose. Something that has also been studied is the detection of cycle slip in the new GPS signals. The advent of the third frequency available from the GPS modernization. Should be explored in the context of cycle slip detection and correction. In the present research the different cycle slip detection and correction methods were studied and t the most suitable for the high accuracy positioning in Brazil was implemented. Two methodologies were selected for the purpose of this research, the first one based on the classical triple difference (TD) method and the second based on the linear combination sequence method. In addition, a third methodology was proposed to improve the TD method. Two experiments were performed, the first one being carried out with simulated data and the second with real data in the period of high ionospheric activity, and for both cases two scenarios were considered: short baseline and long baseline. For simulated short baseline data, the classical TD method, the proposed TD method and the linear combination sequence method presented 100%, 99.91% and 100% accuracy in the detection, resulting in 99.91%, 99.88% and 100% accuracy in the correction of cycle slips, respectively. For the simulated long baseline data, 31.37%, 63.79% and 100% of detection accuracy were obtained, resulting in 49.45%, 95.32% and 100% accuracy in the correction of cycles slips when using the classical TD method, the proposed TD method and the linear combination sequence method, respectively. In the second experiment, conducted with real data, it was possible to evaluate only the improvement in the positioning, being this for short baseline, of 81.71%, 67.08% and 10.79% for the classical TD method, the proposed TD method and linear combination sequence method, respectively. In the long baseline, after correction, the classical TD method obtained a worsening of 12.18%, the proposed TD method provided an improvement of 40.63%, whereas the linear combination sequence method could not show evaluated.
Descrição
Palavras-chave
Perdas de ciclos, Detecção, Correção, Posicionamento relativo, Tripla frequência GPS, Cycle slips, Detection, Repair, Relative positioning, GPS triple-frequency