I'm OK with that. [image: CICS-NC] <http://www.cicsnc.org/>Visit us on Facebook <http://www.facebook.com/cicsnc> *Jim Biard* *Research Scholar* Cooperative Institute for Climate and Satellites NC <http://cicsnc.org/> North Carolina State University <http://ncsu.edu/> NOAA National Centers for Environmental Information <http://ncdc.noaa.gov/> *formerly NOAA’s National Climatic Data Center* 151 Patton Ave, Asheville, NC 28801 e: [email protected] o: +1 828 271 4900
*Connect with us on Facebook for climate <http://www.facebook.com/NOAANCEIclimate> and ocean and geophysics <http://www.facebook.com/NOAANCEIoceangeo> information, and follow us on Twitter at @NOAANCEIclimate <http://www.twitter.com/NOAANCEIclimate>and @NOAANCEIocngeo <http://www.twitter.com/NOAANCEIocngeo>.* On Wed, Aug 29, 2018 at 3:54 PM Ethan Davis <[email protected]> wrote: > Hey Jim, > > How about removing one layer of terminology by using your definitions for > the allowed values of "direction": > > roll: "positive_right_side_up" and "positive_right_side_down". > pitch: "positive_nose_up" and "positive_nose_down". > yaw: "positive_nose_right" and "positive_nose_left". > surge: "positive_forward" and "positive_backward". > sway: "positive_left" and "positive_right". > heave: "positive_up" and "positive_down". > > Cheers, > > Ethan > > On Wed, Aug 29, 2018 at 12:02 PM Jim Biard <[email protected]> wrote: > >> John, >> >> There are a variety of conventions for defining roll, pitch, and yaw out >> there. This is why we are avoiding a specific one. Others have searched >> existing datasets that are using earlier versions of these standard names >> (or not using standard names) and found that they don't all follow the same >> convention. >> >> Ethan, >> >> We purposely aren't answering that question directly because of the issue >> above. I believe that I have consistently followed the convention in which >> clockwise and anticlockwise are rotational directions around a unit vector >> facing the observer, where the X unit vector is in the nominally forward >> direction, the Z axis is in the local up direction, and the Y axis unit >> vector is "Z cross X", which forms a right-handed coordinate system. The >> terms are meaningful and accurate using that convention, but the names >> could be "alpha" and "beta" or "dog" and "cat" as long as they are used >> correctly. >> >> This whole topic is fraught with competing conventions, so we are >> attempting to avoid declaring that only one of them is valid, with it's >> corresponding requirement that everyone follow that one sign convention. >> >> In fact, we could reword things to remove naming the axes X, Y, and Z, >> and perhaps we should. I know of satellite platforms that define their Y >> axis unit vector as pointing forward and the Z axis unit vector as pointing >> down. >> >> Thoughts? >> >> Grace and peace, >> >> Jim >> >> On 8/29/18 1:32 PM, John Helly wrote: >> >> 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 <[email protected]> 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 >> [email protected]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 >> >> >> -- >> [image: CICS-NC] <http://www.cicsnc.org/> Visit us on >> Facebook <http://www.facebook.com/cicsnc> *Jim Biard* >> *Research Scholar* >> Cooperative Institute for Climate and Satellites NC <http://cicsnc.org/> >> North Carolina State University <http://ncsu.edu/> >> NOAA National Centers for Environmental Information >> <http://ncdc.noaa.gov/> >> *formerly NOAA’s National Climatic Data Center* >> 151 Patton Ave, Asheville, NC 28801 >> e: [email protected] >> o: +1 828 271 4900 >> >> *Connect with us on Facebook for climate >> <https://www.facebook.com/NOAANCEIclimate> and ocean and geophysics >> <https://www.facebook.com/NOAANCEIoceangeo> information, and follow us on >> Twitter at @NOAANCEIclimate <https://twitter.com/NOAANCEIclimate> and >> @NOAANCEIocngeo <https://twitter.com/NOAANCEIocngeo>. * >> _______________________________________________ >> CF-metadata mailing list >> [email protected] >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >> >
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