Issues When Averaging Angle Values

In Vic-2D and Vic-3D, some of the inspector tools will cause data to be averaged over a certain area - specifically, the Disc and Rectangle tools. With these tools, when the data is extracted, the resulting values will be a mass average of the values within the disc or rectangle.

 For most magnitude type data - position, displacement, velocity, strain - the average produces a meaningful result. However, caution must be used with angle data. For angle data where a phase boundary is present, causing the value to jump from +90º to -90º or -90º to +90º, averaging can give a nonsensical result. Also, data which has a local context - such as principal strain - may not make sense as an area average. 

In these cases, it may be necessary to average the magnitude data, then recompute the angle or local data; for instance, averaging the magnitude of the three strain components, and then using these new values to calculate principal strains.