Pitch and Roll Calcs

[Govathalay]

I need a quick fix for calculating pitch and roll.

I have a pitch and roll in a certain heading and I want to be able to calculate the respective pitch and roll in any other heading (in the whole 360°). Preferably in Excel.

Cheers
Govathlay

[alkatran]

I need a quick fix for calculating pitch and roll.

I have a pitch and roll in a certain heading and I want to be able to calculate the respective pitch and roll in any other heading (in the whole 360°). Preferably in Excel.

Cheers
Govathlay

Hahahahahaha...

Anyways, could you clarify the question more? Pitch and roll of what?

[honki]

Not sure I understand either.... Perhaps an example of what you're trying to do may help...

[Survey_Bob]

We do this a lot in the survey industry and I found your question while seeking an answer to a question that has been bothering us.
We reduce pitch and roll to inclination (or tilt) at a direction using simple pythagoras. This works fine for small angles of pitch and roll (which is normally what we observe) but possibly not for large angles. This is our dilemma. However here's simple spreadsheet stuff;
=SQRT(pitch^2+roll^2) to give you inclination. This doesn't work well for larger angles as you approach 90°, so we used this (don't know why we used tan - but it seems to work better,
=DEGREES(ATAN(SQRT((TAN(RADIANS(pitch.a1))^2)+(TAN(RADIANS(roll.a1))^2)))) this will give you inclination;
=MOD((DEGREES(ATAN2(-pitch,roll))),360)
this will give you direction of the resultant inclination (sign convention is as follows, we use pitch to define the long axis of a ship and a negative pitch is bow down, stern up. Roll describes the transverse axis of a ship with positive roll as starboard (right) down).
You then need to determine the angular offset from your new ships head (obs head) to the inclination direction.
= IF((inclination direction-obs head)<0,(inclination direction-obs head)+360,inclination direction-obs head)
and then back calculate;
= -1*DEGREES(ATAN((TAN(RADIANS(inclination)))*COS(RADIANS(difference in heading)))) this will give you pitch, and use SIN for roll.

If you've got any ideas about a better way to determine the resultant inclination for bigger angles we'd be grateful!

Good luck.

PS I have since spoken to a colleague who used to be a rocket scientist and he proved the use of
=DEGREES(ATAN(SQRT((TAN(RADIANS(pitch.a1))^2)+(TAN(RADIANS(roll.a1))^2)))) from first principles, so don't use the simple Pythagoras, use this one.