Circular Gauges are usually used to create a chart of circular or semicircular shape with a radial scale. Usually those gauges represent speedometers, watches, volume or engine tuners, etc.
This chart consists of two gauges, representing a speedometer. The bigger gauge is a semicircular gauge (from 0 to 220 degrees) that shows the current speed and the average in the aperture, and the needle is pointing at the current speed value on a radial scale. The interval between the major ticks on this scale is 20 and minor ticks are invisible. Speed is being measured in km per hour. There is a bar marker outside of the radial axis with speed values put from 160 km/h till 180 in orange color (telling the driver to be more careful and attentive) and from 180 km/h till the end of the axis (220) the bar marker is colored in red (which means the most dangerous speed).
The second gauge is a half-circular and small and it holds some additional information It shows the current engine and the average value for it in rpm in the aperture. There is an axis with engine values with trapezoidal major ticks with an interval of 1000 holding the engine values. The needle in pointing at the same value on the axis as shown in the aperture as the current engine.