How to draw in piel or real units

HI all,

I'm trying to figure out how to draw something in pixel or "real" units(inches, mm, etc). what I want is to be able to place an object according to axes units, but not have it change size as I zoom in and out, kind of like a marker.

The big picture:

I'm trying to make a plot that shows a vector value over time (in the case ocean current velocity and direction). The x axis is time, the y axis is magnitude, and at each point I want to draw an arrow pointing in the direction of the vector at that time. However, I don't want the size (or angle) of that arrow to change as you zoom in and out.

Any ideas how I can accomplish this?

See the enclosed PNG for an example with fake data.




Christopher Barker, Ph.D.
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