Lecture 6 - Reference Frames and Coordinate Systems Flashcards
what does a coordinate system allow us to determine
allows us to determine an objects position
how many axis are usually in a coordinate system
usually one axis per measurement dimension
characteristics of axis in coordinate system
they are perpendicular and fixed relative to each other
what are absolute reference frames used for
used to describe landmarks or segment positions
used to describe things relative to the world (e.g floor, gravity)
what can absolute reference frames describe
can describe segment angles
what are relative reference frames used for
used for determining relative segment position and joint angles
what do relative reference frames describe
limb orientation relative to another
what is a joint angle
the orientation of one segment relative to the orientation of another segment and the angle that forms between them
in the right hand coordinate system what does each finger indicate and what is its position
thumb = right = x
1st finger = anterior = y
2nd finger = up = z
what does the x axis describe in terms of coordinate system orientation
mediolateral
what does the y axis describe in terms of coordinate system orientation
anteroposterior
what does the z axis describe in terms of coordinate system orientation
longitudinal
what are the positive directions of coordinate system
right, anterior , up
what is the positive rotation direction using the right hand rule
- thumb pointed in positive axis direction
- fingers curl in positive rotation direction
what is the exceptions to the convention
- knee flexion
- left side ab/adduction
- left side internal / external rotation
