NOV has extensive support for radial (circular) and linear gauges that both share a common programming model. The core concept of gauges is that each gauge consists of two groups of objects – axes and indicators.

The gauge axis is an object that shows a scale and can be positioned in the gauge model space. Gauge axis scales follow the same concept as chart scales and are fully configurable and customizable.

The gauge indicator is an object that pinpoints a certain value or range of values on a specified gauge axis.

The core functionality of a gauge is exposed from the NGauge abstract class, which serves as a base for the NLinearGauge and NRadialGauge classes (describing a linear gauge and radial gauge respectively). The following picture visually illustrates the different elements of a gauge:

The NGauge class exposes two collections – Axes and Indicators that allow you to modify the number of gauge axes and indicators displayed by the gauge. By default each gauge will have one axis and no indicators.

Both the linear and radial gauge use a 2D Cartesian model space, which is transformed to a Cartesian or Polar view space (in the case of radial gauges). In polar space the x value results in an angle which is proportional to the sweep angle, whereas the Y value in model space translates to distance from the scale towards the circle center. The bigger the Y value the closed the coordinate to the center point. The following picture shows how three points are converted from cartesian to polar view space with sweep angle 270: