GLONASS

Definition

GLONASS uses a nominal twenty-four satellites in three orbital planes at about 19,100 km, inclined more steeply than GPS, which gives good coverage at high latitudes. Older satellites separate signals by frequency rather than by code, so receivers need dedicated hardware. Positions are computed in the PZ-90 reference frame and transformed to WGS84 for chart use; the residual difference is well under a metre and negligible for coastal work.