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 <jbi...@cicsnc.org > <mailto:jbi...@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@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
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