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.