National Instruments IMAQ Vision for LabWindows TM /CVI - Manual (Page 55)

Chapter 5 Performing Machine Vision Tasks
© National Instruments Corporation 5-3 IMAQ Vision for LabWindows/CVI User Manual
it appears shifted and rotated in the image you need to process. This
coordinate system is referred to as the measurement coordinate system.
The measurement methods automatically move the ROIs to the correct
position using the position of the measurement coordinate system with
respect to the reference coordinate system. Refer to Chapter 13,
Dimensional Measurements, of the IMAQ Vision Concepts Manual
for information about coordinate systems.
You can build a coordinate transform using edge detection or pattern
matching. The output of the edge detection and pattern matching functions
that build a coordinate system are the origin, angle, and axes direction of
the coordinate system. Some machine vision functions take this output and
adjust the regions of inspection automatically. You can also use these
outputs to programmatically move the regions of inspection relative to the
object.