•Visible satellite constellation at the time of observation
–Small angles weak geometry
–Large angles Strong geometry
•Dilution Of Position (DOP)
–Dilution Of Precision in Position (PDOP)
–Dilution Of Precision in Horizontal position (HDOP)
–Dilution Of Precision in Vertical position (VDOP)
–Dilution Of Precision in Time (TDOP)
–Dilution Of Precision in Geometry (GDOP)