[CF-metadata] yaw angle and orientation

From: Godin, Michael <godin>
Date: Thu, 23 Oct 2008 16:08:23 -0700

Bruno,

Like all decisions made by committee, the decisions on these names seem rather odd now. I think I had originally proposed only "platform_heading" to indicate the "forward looking" direction of a platform, and Roy Lowry wisely pointed out the ambiguity between longitudinal axis and direction of travel.

I countered with "platform_forward_looking_direction".

Nan Galbraith noted that on "ships, true_heading is the gyro reading, corrected for magnetic declination. Course is the direction of the ship's movement, generally acquired from gps."

Chris Webster noted that for aircraft "track_angle is our direction of travel."

After a discussion of true vs magnetic heading, Nan asked "Is there anything wrong with using platform_heading, platform_heading_true (or platform_heading_corrected), and platform_course?"

Jonathan Gregory noted and asked "The problem with "heading" is that it means direction of travel as well as the direction you're pointing in. That's what I understood it to mean when Michael proposed it, and why I asked if it was the same thing as course.
Looking on Google, I find that half the definitions are direction of travel.
Hence "heading" is too confusing, I'd say. How about

platform_orientation (degree) for the direction the platform is pointing in platform_course (degree) for the direction it's travelling in?"

And then (quite clearly out of my mind), I noted: "The one case I can think of a yaw variable being useful and measurable is in the case of towfish, in which yaw is typically defined as the difference between orientation and course. I imagine there may be other similar useful situations, so I'd support adding the variable:
platform_yaw ('difference between orientation and course')(degree)"

I'm not sure why I inexplicably used the word "yaw" when I should have used "attack angle".

Anyway, everyone was sick of the discussion at that point in time, and the variables were added with no further discussion as:

platform_orientation ("pointing direction") (degree)
platform_course ("travel direction") (degree)
platform_yaw ("difference between orientation and course")(degree)

However, the documentation for platform_yaw (wisely?) disagrees with the above.

If I were sane and looking at this today, I'd 1) declare platform_yaw to be "travel direction", 2) make platform_course an alias for platform_yaw, and 3) add a new standard name platform_attack_angle -- which is a variable I'm going to need soon.

Mike
Received on Thu Oct 23 2008 - 17:08:23 BST