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[DPRG] Question about the origin of "theta"

Subject: [DPRG] Question about the origin of "theta"
From: Paradug paradug at gmail.com
Date: Sun Jan 18 19:13:40 CST 2015

Pat,
    When I re-read the "the direction the robot is going" phrase again after 
I pushed the send button, I came to the same conclusion as you. I should 
have said "direction of the front of the robot when describing heading.
Regards,
Doug P.


-----Original Message----- 
From: Patrick R. Michaud
Sent: Sunday, January 18, 2015 2:23 PM
To: Paradug
Cc: dprglist
Subject: Re: [DPRG] Question about the origin of "theta"

On Sun, Jan 18, 2015 at 01:43:43PM -0600, Paradug wrote:
>  I maybe misunderstanding your descriptions of the terms "heading'
> and "bearing'.  Since “aiming”, could be interpreted as “the
> direction of the robot” or as “the direction we want to go”,
> I would describe heading differently . "Heading" is the direction
> that the robot is going (i.e., theta), not the "direction we're
> aiming". Your definition of "Bearing" (i.e., "direction to an
> object" or “direction to a target”) is fine.

I agree, "aiming" isn't the right word for what I was describing, as it 
implies intent.  I meant (and should've said) "direction the robot is 
'pointing'".  In navigational terms, "the direction we want to go" would be 
the "route".

All of which is exactly why I'm looking to tighten up the terms I use a bit. 
:)

I wouldn't want to say that heading is "the direction the robot is going", 
because it might not be "going" anywhere at the moment if it's speed is 
zero, or if it's turning "in place".

Thank you for the references, they're a big help.  I think I'll continue to 
talk in terms of headings for many people I'm working with, as "heading" is 
easier for them to relate to than "theta".  "Heading" also makes good sense 
because many of our competitions have official designations of "north", 
"east", etc., which can effectively act as an external fixed datum 
reference.  (Even for those competitions that don't officially designate 
N/S/E/W, we tend to add our own just to make things easier to talk about.)

On the other hand, if/when we start using the angles to calculate 
coordinates or other kinematic equations, as in the slide examples or at 
DPRG, I'll likely switch to "theta" to provide the more mathematical slant.

Thanks a bunch, very helpful!

Pm 

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