Perhaps one should refer to the discipline of hydrostatics for help with
this?? This paper, pulled from a quick search, has a diagram referencing
the platforms' frame of reference with respect to its center of
gravity.? Sorry if this comment is retrograde.
https://www.hindawi.com/journals/mpe/2010/934714/
J.
On 8/29/18 10:09, Ethan Davis wrote:
> Hi Jim, all,
>
> I'm a bit confused by the "clockwise" and "anticlockwise". You mention
> the orientation of the observer but not the location/orientation of
> the clock. My assumptions (not sure why) for the clock: for roll, the
> observer (who is facing forward) would be facing the clock; for pitch,
> the observer would look right to see the clock; and for yaw, the
> observer would look down to see the clock. That works for your
> definitions of pitch and yaw, but is backwards for roll.
>
> Does "clockwise" add, in some way, another degree of freedom to the
> definition? Does that degree of freedom need to be nailed down in the
> definitions? Or other terms used instead? I don't have any good
> suggestions other than "positive" and "negative".
>
> Cheers,
>
> Ethan
>
> On Wed, Aug 29, 2018 at 9:03 AM Jim Biard <jbiard at cicsnc.org
> <mailto:jbiard at cicsnc.org>> wrote:
>
> Hi.
>
>
> I've finally gotten back to this topic! The definitions below call
> out an attribute named "direction" that is used to specify the
> direction for positive values of the different quantities. We may
> need to add a definition for the attribute to the Conventions. The
> values and meanings for the direction attribute are:
>
> roll: "clockwise" for positive right side up and "anticlockwise"
> for positive right side down.
> pitch: "clockwise" for positive nose up and "anticlockwise" for
> positive nose down.
> yaw: "clockwise" for positive nose right and "anticlockwise" for
> positive nose left.
> surge: "positive" for positive forward and "negative" for positive
> backward.
> sway: "positive" for positive left and "negative" for positive right.
> heave: "positive" for positive up and "negative" for positive down.
>
> And here are the standard name definitions:
>
> platform_roll: 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 (the X axis) that is
> perpendicular to the local vertical axis (the Z 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 X axis. The ?at rest? rotation of the
> platform may change over time. The direction for positive values
> of roll is specified by an attribute named direction. The value of
> the direction attribute is "clockwise" if positive values of roll
> represent the right side of the platform rising as viewed by an
> observer on top of the platform facing forward. The value of the
> direction attribute is "anticlockwise" if positive values of roll
> represent the right side of the platform falling. The
> directionality of roll values is unspecified if no direction
> attribute is present.
>
> platform_pitch: 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 (the Y axis) that is
> perpendicular to both the local vertical axis (the Z 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 Y axis. The ?at rest? rotation of the platform may change over
> time. The direction for positive values of pitch is specified by
> an attribute named direction. The value of the direction attribute
> is "clockwise" if positive values of pitch represent the front of
> the platform rising as viewed by an observer on top of the
> platform facing forward. The value of the direction attribute is
> "anticlockwise" if positive values of pitch represent the front of
> the platform falling. The directionality of pitch values is
> unspecified if no direction attribute is present.
>
> platform_yaw: 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 local vertical axis (the Z
> axis). Yaw is relative to the ?at rest? rotation of the platform
> with respect to the Z axis. The ?at rest? rotation of the platform
> may change over time. The direction for positive values of yaw is
> specified by an attribute named direction. The value of the
> direction attribute is "clockwise" if 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. The value of
> the direction attribute is "anticlockwise" if positive values of
> yaw represent the front of the platform moving to the left. The
> directionality of yaw values is unspecified if no direction
> attribute is present.
>
> platform_surge: 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 (the X axis) that
> is perpendicular to the local vertical axis (the Z 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 X axis. The ?at rest? position of the
> platform may change over time. The direction for positive values
> of surge is specified by an attribute named direction. The value
> of the direction attribute is "positive" if positive values of
> surge represent the platform moving forward as viewed by an
> observer on top of the platform facing forward. The value of the
> direction attribute is "negative" if positive values of surge
> represent the platform moving backward. The directionality of
> surge values is unspecified if no direction attribute is present.
>
> platform_sway: 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 (the Y axis) that is
> perpendicular to both the local vertical axis (the Z 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 Y
> axis. The ?at rest? position of the platform may change over
> time.? The direction for positive values of sway is specified by
> an attribute named direction. The value of the direction attribute
> is "positive" if positive values of sway represent the platform
> moving left as viewed by an observer on top of the platform facing
> forward. The value of the direction attribute is "negative" if
> positive values of sway represent the platform moving right. The
> directionality of sway values is unspecified if no direction
> attribute is present.
>
> platform_heave: 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
> (the Z axis). Heave is relative to the ?at rest? position of the
> platform with respect to the Z axis. The ?at rest? position of the
> platform may change over time.? The direction for positive values
> of heave is specified by an attribute named direction. The value
> of the direction attribute is "positive" if positive values of
> heave represent the platform moving up as viewed by an observer on
> top of the platform facing forward. The value of the direction
> attribute is "negative" if positive values of heave represent the
> platform moving down. The directionality of heave values is
> unspecified if no direction attribute is present.
>
> 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).
>
> platform_roll_rate: 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 (the X
> axis) that is perpendicular to the local vertical axis (the Z
> axis) and is coplanar with the nominal forward motion direction of
> the platform. Roll rate might not include changes in the ?at rest?
> rotation of the platform, which may change over time. The
> direction for positive values of roll rate is specified by an
> attribute named direction. The value of the direction attribute is
> "clockwise" if 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. The value of the direction attribute is
> "anticlockwise" if positive values of roll rate represent the
> right side of the platform falling. The directionality of roll
> rate values is unspecified if no direction attribute is present.
>
> platform_pitch_rate: 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 (the Y axis) that is perpendicular to both the local vertical
> axis (the Z axis) and the nominal forward motion direction of the
> platform. Pitch rate might not include changes in the ?at rest?
> rotation of the platform, which may change over time. The
> direction for positive values of pitch rate is specified by an
> attribute named direction. The value of the direction attribute is
> "clockwise" if positive values of pitch rate represent the front
> of the platform rising as viewed by an observer on top of the
> platform facing forward. The value of the direction attribute is
> "anticlockwise" if positive values of pitch rate represent the
> front of the platform falling. The directionality of pitch rate
> values is unspecified if no direction attribute is present.
>
> platform_yaw_rate: 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 local
> vertical axis (the Z axis). Yaw rate might not include changes in
> the ?at rest? rotation of the platform, which may change over
> time. The direction for positive values of yaw rate is specified
> by an attribute named direction. The value of the direction
> attribute is "clockwise" if 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. The value of the
> direction attribute is "anticlockwise" if positive values of yaw
> rate represent the front of the platform moving to the left. The
> directionality of yaw rate values is unspecified if no direction
> attribute is present.
>
> platform_surge_rate: 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 (the X axis) that is perpendicular to the local vertical
> axis (the Z axis) and is coplanar with the nominal forward motion
> direction of the platform. Surge rate might not include changes in
> the ?at rest? position of the platform, which may change over
> time. The direction for positive values of surge rate is specified
> by an attribute named direction. The value of the direction
> attribute is "positive" if positive values of surge rate represent
> the platform moving forward as viewed by an observer on top of the
> platform facing forward. The value of the direction attribute is
> "negative" if positive values of surge rate represent the platform
> moving backward. The directionality of surge rate values is
> unspecified if no direction attribute is present.
>
> platform_sway_rate: 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
> (the Y axis) that is perpendicular to both the local vertical axis
> (the Z axis) and the nominal forward motion direction of the
> platform. Sway rate might not include changes in the ?at rest?
> position of the platform, which may change over time. The
> direction for positive values of sway rate is specified by an
> attribute named direction. The value of the direction attribute is
> "positive" if positive values of sway rate represent the platform
> moving left as viewed by an observer on top of the platform facing
> forward. The value of the direction attribute is "negative" if
> positive values of sway rate represent the platform moving right.
> The directionality of sway rate values is unspecified if no
> direction attribute is present.
>
> platform_heave_rate: 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 (the Z axis). Heave rate might not include
> changes in the ?at rest? position of the platform, which may
> change over time. The direction for positive values of heave rate
> is specified by an attribute named direction. The value of the
> direction attribute is "positive" if positive values of heave rate
> represent the platform moving up as viewed by an observer on top
> of the platform facing forward. The value of the direction
> attribute is "negative" if positive values of heave rate represent
> the platform moving down. The directionality of heave rate values
> is unspecified if no direction attribute is present.
>
>
> Grace and peace,
>
>
> Jim
>
>
>
>
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
--
John Helly, University of California, San Diego / San Diego Supercomputer Center / Scripps Institution of Oceanography / 760 840 8660 mobile / http://www.sdsc.edu/~hellyj
ORCID ID: orcid.org/0000-0002-3779-0603
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.cgd.ucar.edu/pipermail/cf-metadata/attachments/20180829/f841720d/attachment-0001.html>
Received on Wed Aug 29 2018 - 11:32:48 BST
