[slijin]

If by "absolute angle" you are referring to the angular position of the robot with respect to field boundaries, then the answer is that no, you cannot directly measure the robot's angular velocity with an encoder. The quadrature encoders distributed in the KoP measure the angular velocity of a rotating shaft relative to the encoder's mount.

In other words, because you can only use the encoder to measure the angular velocity of one object relative to another, you can't use it to measure that of the robot relative to the field, because you can't mount it on the field.

A better option would be to use a gyro sensor.