The MINC standard gives some special status to the concept of an
image. There is nothing inherent in NetCDF that suggests any special
status for particular dimensions, but it can be convenient to place
limitations on what can vary over which dimensions in an imaging
context. For example, the requirement that the variables that specify
how to rescale images (see later section on pixel values) not vary
with image dimensions means that we can treat the image as a simple
unit. In the simplest case, the image dimensions are simply the two
fastest varying dimensions of the MIimage variable.
It can also be helpful to allow for vector fields -- images or image
volumes that have a vector of values at each point. A simple example
of a vector field is an RGB image. At each point in space, there are
three values: red, green and blue. The dimension
MIvector_dimension is used for the components of the vector and
it should be the fastest varying dimension in the MIimage variable. If
it is present, then the three fastest varying dimensions of MIimage
are the image dimensions.