Re: [CF-metadata] Platform Heave

[Lowry, Roy K.]

Hi Jim,


Interesting article that answers some of my questions about what we've been 
defining here in terms of platform-local axes and 'real world' co-ordinate 
reference systems.


Cheers, Roy.


I have now retired but will continue to be active through an Emeritus 
Fellowship using this e-mail address.



From: CF-metadata  on behalf of Jim Biard 

Sent: 13 September 2018 19:39
To: cf-metadata@cgd.ucar.edu
Subject: Re: [CF-metadata] Platform Heave


I only just located this wikipedia article. It describes the different axes 
conventions that are in common use and the differences between them.


https://en.wikipedia.org/wiki/Axes_conventions

[https://upload.wikimedia.org/wikipedia/commons/thumb/6/67/Plane.svg/1200px-Plane.svg.png]

Axes conventions - Wikipedia
en.wikipedia.org
In ballistics and flight dynamics, axes conventions are standardized ways of 
establishing the location and orientation of coordinate axes for use as a frame 
of reference.Mobile objects are normally tracked from an external frame 
considered fixed. Other frames can be defined on those mobile objects to deal 
with relative positions for other objects.




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 
 on 
behalf of John Graybeal 

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 

Re: [CF-metadata] Platform Heave

[Jim Biard]

I only just located this wikipedia article. It describes the different 
axes conventions that are in common use and the differences between them.



https://en.wikipedia.org/wiki/Axes_conventions


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  on behalf of 
John Graybeal 

*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 

Re: [CF-metadata] Platform Heave

[Jim Biard]

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  on behalf of 
John Graybeal 

*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 

Re: [CF-metadata] Platform Heave

[Jim Biard]

Hi.


Good catch, Jonathan! I botched the yaw definitions. It should be 'about 
the local vertical axis'.



I defined each rotation in isolation, as I found it difficult to deal 
with all of the different issues AND find language that would be clear 
as to which axis is being referred to. The direction in relation to an 
extrinsic coordinate system of a given body or motion frame axis after a 
rotation about some other axis is dependent on the order of application. 
If you follow a roll-pitch-yaw sequence, then yaw is not around the 
local vertical axis, nor is pitch around an axis perpendicular to the 
local vertical axis. Likewise, if you follow a yaw-pitch-roll sequence, 
the pitch axis is not perpendicular to the nominal forward motion axis, 
nor is the roll axis perpendicular to the local vertical axis.



If people think it's important to note that these definitions are 
describing the rotations in isolation, I'm happy for someone to take a 
stab at that verbiage.



Grace and peace,


Jim


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  on behalf of 
John Graybeal 

*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 

Re: [CF-metadata] Platform Heave

[Lowry, Roy K.]

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  on behalf of John Graybeal 

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 

Re: [CF-metadata] Platform Heave

[John Graybeal]

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