This is an assessment of colour system that is more usually used to set tolerances once the hue, chroma and lightness limits are established.
While CIELAB (L*a*b*) uses Cartesian coordinates to calculate a colour in a colour space, CIELAB (L*C*h) uses polar coordinates. This colour expression can be derived from CIELAB (L*a*b*). The L*, as before defines lightness, C* specifies chroma and h denotes hue angle, an angular measurement.
The L*C*h expression offers an advantage over L*a*b* in that it is very easy to relate to the earlier systems based on physical samples, like the Munsell Colour Scale.