Satellites Bookmark |
Satellites bookmark is intended for displaying the scheme of conditional arrangement of satellites on heavenly sphere and allows to estimate a degree of reliability, accuracy of measurements. Accuracy of definition of coordinates, numbers of satellites and relative size of their signal are marked here.
Factors of accuracy lowering (satellite geometry): - PDOP (Position Dilution Of Precision). It is the geometrical factor. To an ideal arrangement of satellites the value PDOP = 1 corresponds. Suitable for navigation the values PDOP <6.0 are considered. - HDOP (Horizontal Dilution Of Precision). It is applied in bidimentional navigation. Suitable for navigation the values HDOP <4.0 are considered. - VDOP (Horizontal Dilution Of Precision). It is the vertical geometrical factor. Suitable for navigation the values VDOP <4.5 are considered. - TDOP (Time Dilution Of Precision). It is the time factor. Suitable for navigation the values TDOP <2.0 are considered. The reasons of GPS errors: - Noise of the receiver; - Tropospheric refraction; - Reflected signals; - Error of hours; - Error of ephemeris; - Ionospheric refraction; - Selective access. For the devices connected by the GARMIN protocol, factors of accuracy lowering are transferred in meters; the number of visible satellites, the almanac and the scheme of relative force of signals of satellites are not shown.
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