Vector direction plot meaning

[CellRus]

Dear William,

I'm trying to look for some explanation on what exactly does a vector direction plot do but could not find it online so would love if you could explain it to me. 

I understand roughly that it plots the angle between vectors from -180 and 180. But what I'm unclear is what are the angles relative to? Are they relative to the average direction of the entire flow? Or are they relative to the surrounding local vectors?

Thank you very much

Hal

[thielickeoptolution]

Dear Hal, they are relative to the coordinate system of the input images.

[Minerva Ferrer]

Hello William and Hal,

Thank you for initiating this conversation. I am relatively new to using PIVlab, so I apologise in advance if my questions are too basic. Currently, I am attempting to calculate the mean vector direction (in degrees) over a time series within a circular region of interest. As Hal mentioned, I am finding the output difficult to interpret, and I have not been able to locate the coordinate system referred to above. I would also like to clarify whether each output is defined relative to a fixed coordinate system or whether it represents a continuous measure relative to the previous time point. This distinction is important for my analysis, as I aim to describe continuous changes over time.

Thank you very much in advance, 

Minerva

El dia dijous, 18 de setembre del 2025 a les 12:39:20 UTC+2, thielickeoptolution va escriure: