And regarding the question marks - they started as ASCII full quotes. I
have no idea how they got translated into question marks. I blame
unicode for everything. ;-)
On 9/13/18 12:15 PM, Lowry, Roy K. wrote:
Hi John,
Your Q2 has been discussed at length. The local vertical axis is
indeed local to the platform, as are the axes running front to back
and left to right.
Your eagle eyes have indeed spotted something I missed in the yaw
definition ' 'Yaw is a rotation about the axis of rotation' should I
think read 'Yaw is a rotation about the local vertical axis'.
I HATE 'smart' quotes and Microsoft's mission to make every quote
smart through auto-correction!
Cheers, Roy.
I have now retired but will continue to be active through an Emeritus
Fellowship using this e-mail address.
------------------------------------------------------------------------
*From:* CF-metadata <cf-metadata-boun...@cgd.ucar.edu> on behalf of
John Graybeal <jbgrayb...@mindspring.com>
*Sent:* 13 September 2018 16:38
*To:* CF Metadata List
*Subject:* Re: [CF-metadata] Platform Heave
It’s a brilliant effort, if I may say. I’ve been following and
appreciating it (wanted it for a long time!) and I think it is very close.
If I may say so, it deserves a bit of time for everyone to catch up,
before enshrinement. I have two questions I’d like to ask, and one
editing nit.
Question 1: The last version I found is enclosed, but I can’t tell if
it is the last version. (Please note the long tails of the emails make
it extremely time-consuming to find the content when trying to catch
up. Hence I have sent this without the long tail.)
This version does not seem to address Nan’s suggestion to put the
platform description after the roll/pitch/etc description, which I
also like. Still, I can see advantages both ways.
Question 2: The one concern I have, sorry if you dealt with it
thoroughly, is about the expression in each definition that reads
something like "Roll is a rotation about an axis that is perpendicular
to the local vertical axis and is coplanar with the nominal forward
motion direction of the platform.” I may be mis-remembering, but from
my airplane navigation days my understanding is that the role is
around the axis that points out the front of the airplane. If the
airplane is pitched up, the roll is around the pitched-up vector; if
the airplane is yawing to the right, the roll is around the actual
direction, not the travel direction. This is important at small
scales when dealing with the spherical coordinate math necessary to
point telescopes; it’s important at large scales if you imagine a
fighter jet flying vertically up or down, and executing a roll (the
roll axis is definitely not perpendicular to the local vertical axis
in this case, unless you mean “platform local”, which I believe is how
it is defined and I’m pretty sure is how it is measured by the
accelerometers). I believe that satellites work the same way
also—once they define ‘front’, the measurements and calculations for
roll are all around where front is, and similar patterns apply for
pitch (measured relative to a line perpendicular to front-back axis
directly through the wings) and yaw (measured around an axis vertical
to the airplane local—note that the definitions for yaw include "Yaw
is a rotation about the axis of rotation”, and appear to have lost the
description of what the axis of rotation *is*.
I cite Wikipedia as my authority, not just because it matches my
memory but also because it is footnoted, and refers to both airplanes
and satellites using this reference frame.
Finally, my editing nit is that these definitions have replaced smart
apostrophes with question marks, I assume dumb apostrophes are the
order of the day.
John
platform_roll_starboard_down: Platform is a structure or vehicle that
serves as a base for mounting sensors. Platforms include, but are not
limited to, satellites, aeroplanes, ships, buoys, ground stations, and
masts. Roll is a rotation about an axis that is perpendicular to the
local vertical axis and is coplanar with the nominal forward motion
direction of the platform. Roll is relative to the ?at rest? rotation
of the platform with respect to the axis of rotation. The ?at rest?
rotation of the platform may change over time. "Starboard down"
indicates that positive values of roll represent the right side of the
platform falling as viewed by an observer on top of the platform
facing forward.
platform_roll_starboard_up: Platform is a structure or vehicle that
serves as a base for mounting sensors. Platforms include, but are not
limited to, satellites, aeroplanes, ships, buoys, ground stations, and
masts. Roll is a rotation about an axis that is perpendicular to the
local vertical axis and is coplanar with the nominal forward motion
direction of the platform. Roll is relative to the ?at rest? rotation
of the platform with respect to the axis of rotation. The ?at rest?
rotation of the platform may change over time. "Starboard up"
indicates that positive values of roll represent the right side of the
platform rising as viewed by an observer on top of the platform facing
forward.
platform_roll_rate_starboard_down: Platform is a structure or vehicle
that serves as a base for mounting sensors. Platforms include, but are
not limited to, satellites, aeroplanes, ships, buoys, ground stations,
and masts. "Roll rate" is the rate of rotation about an axis that is
perpendicular to the local vertical axis and is coplanar with the
nominal forward motion direction of the platform. Roll rate might not
include changes to the ?at rest? rotation of the platform with respect
to the axis of rotation, which may change over time. "Starboard down"
indicates that positive values of roll rate represent the right side
of the platform falling as viewed by an observer on top of the
platform facing forward.
platform_roll_rate_starboard_up: Platform is a structure or vehicle
that serves as a base for mounting sensors. Platforms include, but are
not limited to, satellites, aeroplanes, ships, buoys, ground stations,
and masts. "Roll rate" is the rate of rotation about an axis that is
perpendicular to the local vertical axis and is coplanar with the
nominal forward motion direction of the platform. Roll rate might not
include changes to the ?at rest? rotation of the platform with respect
to the axis of rotation, which may change over time. "Starboard up"
indicates that positive values of roll rate represent the right side
of the platform rising as viewed by an observer on top of the platform
facing forward.
platform_pitch_fore_up: Platform is a structure or vehicle that serves
as a base for mounting sensors. Platforms include, but are not limited
to, satellites, aeroplanes, ships, buoys, ground stations, and masts.
Pitch is a rotation about an axis that is perpendicular to both the
local vertical axis and the nominal forward motion direction of the
platform. Pitch is relative to the ?at rest? rotation of the platform
with respect to the axis of rotation. The ?at rest? rotation of the
platform may change over time. "Fore up" indicates that positive
values of pitch represent the front of the platform rising as viewed
by an observer on top of the platform facing forward.
platform_pitch_fore_down: Platform is a structure or vehicle that
serves as a base for mounting sensors. Platforms include, but are not
limited to, satellites, aeroplanes, ships, buoys, ground stations, and
masts. Pitch is a rotation about an axis that is perpendicular to both
the local vertical axis and the nominal forward motion direction of
the platform. Pitch is relative to the ?at rest? rotation of the
platform with respect to the axis of rotation. The ?at rest? rotation
of the platform may change over time. "Fore down" indicates that
positive values of pitch represent the front of the platform falling
as viewed by an observer on top of the platform facing forward.
platform_pitch_rate_fore_up: Platform is a structure or vehicle that
serves as a base for mounting sensors. Platforms include, but are not
limited to, satellites, aeroplanes, ships, buoys, ground stations, and
masts. "Pitch rate" is the rate of rotation about an axis that is
perpendicular to both the local vertical axis and the nominal forward
motion direction of the platform. Pitch rate might not include changes
to the ?at rest? rotation of the platform with respect to the axis of
rotation, which may change over time. "Fore up" indicates that
positive values of pitch rate represent the front of the platform
rising as viewed by an observer on top of the platform facing forward.
platform_pitch_rate_fore_down: Platform is a structure or vehicle that
serves as a base for mounting sensors. Platforms include, but are not
limited to, satellites, aeroplanes, ships, buoys, ground stations, and
masts. "Pitch rate" is the rate of rotation about an axis that is
perpendicular to both the local vertical axis and the nominal forward
motion direction of the platform. Pitch rate might not include changes
to the ?at rest? rotation of the platform with respect to the axis of
rotation, which may change over time. "Fore down" indicates that
positive values of pitch rate represent the front of the platform
falling as viewed by an observer on top of the platform facing forward.
platform_yaw_fore_starboard: Platform is a structure or vehicle that
serves as a base for mounting sensors. Platforms include, but are not
limited to, satellites, aeroplanes, ships, buoys, ground stations, and
masts. Yaw is a rotation about the axis of rotation. Yaw is relative
to the ?at rest? rotation of the platform with respect to the axis of
rotation. The ?at rest? rotation of the platform may change over time.
"Fore starboard" indicates that positive values of yaw represent the
front of the platform moving to the right as viewed by an observer on
top of the platform facing forward.
platform_yaw_fore_port: Platform is a structure or vehicle that serves
as a base for mounting sensors. Platforms include, but are not limited
to, satellites, aeroplanes, ships, buoys, ground stations, and masts.
Yaw is a rotation about the axis of rotation. Yaw is relative to the
?at rest? rotation of the platform with respect to the axis of
rotation. The ?at rest? rotation of the platform may change over time.
"Fore port" indicates that positive values of yaw represent the front
of the platform moving to the left as viewed by an observer on top of
the platform facing forward.
platform_yaw_rate_fore_starboard: Platform is a structure or vehicle
that serves as a base for mounting sensors. Platforms include, but are
not limited to, satellites, aeroplanes, ships, buoys, ground stations,
and masts. "Yaw rate" is the rate of rotation about the axis of
rotation. Yaw rate might not include changes to the ?at rest? rotation
of the platform with respect to the axis of rotation, which may change
over time. "Fore starboard" indicates that positive values of yaw rate
represent the front of the platform moving to the right as viewed by
an observer on top of the platform facing forward.
platform_yaw_rate_fore_port: Platform is a structure or vehicle that
serves as a base for mounting sensors. Platforms include, but are not
limited to, satellites, aeroplanes, ships, buoys, ground stations, and
masts. "Yaw rate" is the rate of rotation about the axis of rotation.
Yaw rate might not include changes to the ?at rest? rotation of the
platform with respect to the axis of rotation, which may change over
time. "Fore port" indicates that positive values of yaw rate represent
the front of the platform moving to the left as viewed by an observer
on top of the platform facing forward.
platform_surge_fore: Platform is a structure or vehicle that serves as
a base for mounting sensors. Platforms include, but are not limited
to, satellites, aeroplanes, ships, buoys, ground stations, and masts.
Surge is a displacement along an axis that is perpendicular to the
local vertical axis and is coplanar with the nominal forward motion
direction of the platform. Surge is relative to the ?at rest? position
of the platform with respect to the axis of displacement. The ?at
rest? position of the platform may change over time. "Fore" indicates
that positive values of surge represent the platform moving forward as
viewed by an observer on top of the platform facing forward.
platform_surge_aft: Platform is a structure or vehicle that serves as
a base for mounting sensors. Platforms include, but are not limited
to, satellites, aeroplanes, ships, buoys, ground stations, and masts.
Surge is a displacement along an axis that is perpendicular to the
local vertical axis and is coplanar with the nominal forward motion
direction of the platform. Surge is relative to the ?at rest? position
of the platform with respect to the axis of displacement. The ?at
rest? position of the platform may change over time. "Aft" indicates
that positive values of surge represent the platform moving backward
as viewed by an observer on top of the platform facing forward.
platform_surge_rate_fore: Platform is a structure or vehicle that
serves as a base for mounting sensors. Platforms include, but are not
limited to, satellites, aeroplanes, ships, buoys, ground stations, and
masts. "Surge rate" is the rate of displacement along an axis that is
perpendicular to the local vertical axis and is coplanar with the
nominal forward motion direction of the platform. Surge rate might not
include changes to the ?at rest? position of the platform with respect
to the axis of displacement, which may change over time. "Fore"
indicates that positive values of surge rate represent the platform
moving forward as viewed by an observer on top of the platform facing
forward.
platform_surge_rate_aft: Platform is a structure or vehicle that
serves as a base for mounting sensors. Platforms include, but are not
limited to, satellites, aeroplanes, ships, buoys, ground stations, and
masts. "Surge rate" is the rate of displacement along an axis that is
perpendicular to the local vertical axis and is coplanar with the
nominal forward motion direction of the platform. Surge rate might not
include changes to the ?at rest? position of the platform with respect
to the axis of displacement, which may change over time. "Aft"
indicates that positive values of surge rate represent the platform
moving backward as viewed by an observer on top of the platform facing
forward.
platform_sway_port: Platform is a structure or vehicle that serves as
a base for mounting sensors. Platforms include, but are not limited
to, satellites, aeroplanes, ships, buoys, ground stations, and masts.
Sway is a displacement along an axis that is perpendicular to both the
local vertical axis and the nominal forward motion direction of the
platform. Sway is relative to the ?at rest? position of the platform
with respect to the axis of displacement. The ?at rest? position of
the platform may change over time. "Port" indicates that positive
values of sway represent the platform moving left as viewed by an
observer on top of the platform facing forward.
platform_sway_starboard: Platform is a structure or vehicle that
serves as a base for mounting sensors. Platforms include, but are not
limited to, satellites, aeroplanes, ships, buoys, ground stations, and
masts. Sway is a displacement along an axis that is perpendicular to
both the local vertical axis and the nominal forward motion direction
of the platform. Sway is relative to the ?at rest? position of the
platform with respect to the axis of displacement. The ?at rest?
position of the platform may change over time. "Starboard" indicates
that positive values of sway represent the platform moving right as
viewed by an observer on top of the platform facing forward.
platform_sway_rate_port: Platform is a structure or vehicle that
serves as a base for mounting sensors. Platforms include, but are not
limited to, satellites, aeroplanes, ships, buoys, ground stations, and
masts. "Sway rate" is the rate of displacement along an axis that is
perpendicular to both the local vertical axis and the nominal forward
motion direction of the platform. Sway rate may not include changes to
the ?at rest? position of the platform with respect to the axis of
displacement, which may change over time. "Port" indicates that
positive values of sway rate represent the platform moving left as
viewed by an observer on top of the platform facing forward.
platform_sway_rate_starboard: Platform is a structure or vehicle that
serves as a base for mounting sensors. Platforms include, but are not
limited to, satellites, aeroplanes, ships, buoys, ground stations, and
masts. "Sway rate" is a displacement along an axis that is
perpendicular to both the local vertical axis and the nominal forward
motion direction of the platform. Sway rate may not include changes to
the ?at rest? position of the platform with respect to the axis of
displacement, which may change over time. "Starboard" indicates that
positive values of sway rate represent the platform moving right as
viewed by an observer on top of the platform facing forward.
platform_heave_up: Platform is a structure or vehicle that serves as a
base for mounting sensors. Platforms include, but are not limited to,
satellites, aeroplanes, ships, buoys, ground stations, and masts.
Heave is a displacement along the local vertical axis. Heave is
relative to the ?at rest? position of the platform with respect to the
axis of displacement. The ?at rest? position of the platform may
change over time. "Up" indicates that positive values of heave
represent the platform moving up as viewed by an observer on top of
the platform facing forward.
platform_heave_down: Platform is a structure or vehicle that serves as
a base for mounting sensors. Platforms include, but are not limited
to, satellites, aeroplanes, ships, buoys, ground stations, and masts.
Heave is a displacement along the local vertical axis. Heave is
relative to the ?at rest? position of the platform with respect to the
axis of displacement. The ?at rest? position of the platform may
change over time. "Down" indicates that positive values of heave
represent the platform moving down as viewed by an observer on top of
the platform facing forward.
platform_heave_rate_up: Platform is a structure or vehicle that serves
as a base for mounting sensors. Platforms include, but are not limited
to, satellites, aeroplanes, ships, buoys, ground stations, and masts.
"Heave rate" is the rate of displacement along the local vertical
axis. Heave rate may not include changes to the ?at rest? position of
the platform with respect to the axis of displacement, which may
change over time. "Up" indicates that positive values of heave rate
represent the platform moving up as viewed by an observer on top of
the platform facing forward.
platform_heave_rate_down: Platform is a structure or vehicle that
serves as a base for mounting sensors. Platforms include, but are not
limited to, satellites, aeroplanes, ships, buoys, ground stations, and
masts. "Heave rate" is the rate of displacement along the local
vertical axis. Heave rate may not include changes to the ?at rest?
position of the platform with respect to the axis of displacement,
which may change over time. "Down" indicates that positive values of
heave rate represent the platform moving down as viewed by an observer
on top of the platform facing forward.
platform_course: Platform is a structure or vehicle that serves as a
base for mounting sensors. Platforms include, but are not limited to,
satellites, aeroplanes, ships, buoys, ground stations, and masts.
Course is the clockwise angle with respect to North of the nominal
forward motion direction of the platform.
platform_orientation: Platform is a structure or vehicle that serves
as a base for mounting sensors. Platforms include, but are not limited
to, satellites, aeroplanes, ships, buoys, ground stations, and masts.
Orientation is the clockwise angle with respect to North of the
longitudinal (front-to-back) axis of the platform, which may be
different than the platform course (see platform_course).
---------------------------------------
John Graybeal
jbgrayb...@mindspring.com
650-450-1853
skype: graybealski
linkedin: http://www.linkedin.com/in/johngraybeal/
<http://www.linkedin.com/in/johngraybeal/>
<http://www.linkedin.com/in/johngraybeal/>
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