In the automation of identification of landscape features the vaguenessarises from the fact that the attributes and parameters that make up a landscape vary over space andscale. In most of existing studies, these two ...In the automation of identification of landscape features the vaguenessarises from the fact that the attributes and parameters that make up a landscape vary over space andscale. In most of existing studies, these two kinds of vagueness are studied separately. This paperinvestigates their combination in identification of coast landscape units. Fuzzy set theory is usedto describe the vagueness of geomorphic features due to the continuity in space. The vaguenessresulted from the scale of measurement is evaluated by statistic indicators. The differences offuzzy objects derived from data at differing resolutions (in size from 3 X 3 cells to 25 X 25 cells)are studied in order to examine these higher-order uncertainties.展开更多
The ionospheric delay error is a major error source which degrades the positioning accuracy in network real time kinematic (RTK) positioning over a long distance. Different approaches are proposed to estimate GPS erro...The ionospheric delay error is a major error source which degrades the positioning accuracy in network real time kinematic (RTK) positioning over a long distance. Different approaches are proposed to estimate GPS errors based on GPS reference network, such as virtual reference stations (VRSs) and network corrections. A new method is used to model the ionospheric total electronic content (TEC) distribution in space. Unlike most ionospheric models, only the ionospheric delays along the satellite tracks are modelled. Therefore, the models are of high precise resolution of the ionospheric TEC distribution in both spatial and temporal scales. A new algorithm is used to solve the equation singularity problem. Experiments demonstrate that the new ionospheric correction method can be used to describe the ionospheric variation at a low latitude area where ionospheric activities are strong. Also, the accuracy of the ionospheric model is enough to support centimeter-level positioning within the network. As ionospheric models are satellite-based models (each satellite has one model), the model parameters can be easily incorporated with the existing differential GPS Radio Technical Commission for Maritime Service (DGPS RTCM) 104 format.展开更多
文摘In the automation of identification of landscape features the vaguenessarises from the fact that the attributes and parameters that make up a landscape vary over space andscale. In most of existing studies, these two kinds of vagueness are studied separately. This paperinvestigates their combination in identification of coast landscape units. Fuzzy set theory is usedto describe the vagueness of geomorphic features due to the continuity in space. The vaguenessresulted from the scale of measurement is evaluated by statistic indicators. The differences offuzzy objects derived from data at differing resolutions (in size from 3 X 3 cells to 25 X 25 cells)are studied in order to examine these higher-order uncertainties.
文摘The ionospheric delay error is a major error source which degrades the positioning accuracy in network real time kinematic (RTK) positioning over a long distance. Different approaches are proposed to estimate GPS errors based on GPS reference network, such as virtual reference stations (VRSs) and network corrections. A new method is used to model the ionospheric total electronic content (TEC) distribution in space. Unlike most ionospheric models, only the ionospheric delays along the satellite tracks are modelled. Therefore, the models are of high precise resolution of the ionospheric TEC distribution in both spatial and temporal scales. A new algorithm is used to solve the equation singularity problem. Experiments demonstrate that the new ionospheric correction method can be used to describe the ionospheric variation at a low latitude area where ionospheric activities are strong. Also, the accuracy of the ionospheric model is enough to support centimeter-level positioning within the network. As ionospheric models are satellite-based models (each satellite has one model), the model parameters can be easily incorporated with the existing differential GPS Radio Technical Commission for Maritime Service (DGPS RTCM) 104 format.
