Each ScanImage scanner (ResScan / LinScan) uses its own normalized coordinate system to allow for different field of views. The scanner coordinates are mapped into a common reference space. The reference space is used in the ScanImage API and all GUIs exposed to the user.
This article gives an overview about the ScanImage terminology and
The scanner coordinates are a normalized coordinate system with x and y extending from 0 to 1. This extent is regardless of the size and the aspect ratio of the actual scanner field of view and defines the maximum addressable space of the scanner.
The scanner spaces are mapped into a common reference space via affine transformations. All Scanfields and stimuli are defined in reference space and then mapped back into the appropriate scanner space to control the scanner hardware. The aspect ratios in reference space show the true proportions of the scanners in the system.
To simplify the alignment of the scanners relative to each other, ScanImage features an Alignment GUI. After a successful alignment, ScanImage stores the affine matrices used for the transformation as properties in the imaging system objects: