I lack some 3 dimensional understanding.

What are these angles referenced to? For example, R, P, Y all start from 0, plane is flying horizontal, then it inclines its nose by 90 degrees, moving vertical like a rocket.
Now pitch is 90 degrees, but what now determines the roll?
While moving horizontal, roll may be the angle between the normal vector of the earth's surface and the airplane's up vector.
But when pitch = 90 degrees, what is roll?

Update: Can any (yaw, pitch, roll) triple set exactly describe the attitude/orientation of an aircraft? Which sensors are needed to get a quadcopter's (or any other aircraft's) orientation?

I lack some 3 dimensional understanding.

What are these angles referenced to? For example, R, P, Y all start from 0, plane is flying horizontal, then it inclines its nose by 90 degrees, moving vertical like a rocket.
Now pitch is 90 degrees, but what now determines the roll?
While moving horizontal, roll may be the angle between the normal vector of the earth's surface and the airplane's up vector.
But when pitch = 90 degrees, what is roll?

Update: Can any (yaw, pitch, roll) triple set exactly describe the attitude/orientation of an aircraft?

I lack some of 3 dimensional understanding, and now I experience some problem while trying to understand roll yaw and pitch angles. If there is somebody who may provide me some source recommendations (animations, videos etc.) or explain it from here I would be appreciated.

What are all these angles referenced to? For example, R, P, Y all start from 0, plane is flying straight (moving horizontal/parallel to the surface of earth) then it inclines its nose by 90 degrees (moving vertical to the ground, like a rocket launching).

I understand that pitch is 90 degrees now, however, what now determines the roll?

While moving horizontal to the surface of the earth, I can imagine it (roll) as something like the angle between the normal vector of the earth surface and the normal vector of the plane body (towards upper surface of plane).

But in the pitch = 90 degrees case I cannot easily understand how can I think the roll.

Thanks in advance.

Update to the question: I wonder whether any (yaw, pitch, roll) triple set exactly describes the attitude/orientation of an aircraft or not. And if anybody has experience about sensors, can I achieve to get a quadcopter's (or any other air vehicle) exact orientation in the air at any time? Which sensors are needed to do this and how?

I lack some 3 dimensional understanding.

What are these angles referenced to? For example, R, P, Y all start from 0, plane is flying horizontal, then it inclines its nose by 90 degrees, moving vertical like a rocket.
Now pitch is 90 degrees, but what now determines the roll?
While moving horizontal, roll may be the angle between the normal vector of the earth's surface and the airplane's up vector.
But when pitch = 90 degrees, what is roll?

Update: Can any (yaw, pitch, roll) triple set exactly describe the attitude/orientation of an aircraft? Which sensors are needed to get a quadcopter's (or any other aircraft's) orientation?