## Output cube in details

The gridding engine can write the resulting cube in either Position-Position-Velocity order (hereafter LMV) or Velocity-Position-Position (hereafter VLM). The default is LMV. The table describes both possibilities.

Table: Advantages (+) and disadvantages (-) of LMV and VLM-ordered Class cubes
# | Position-Position-Velocity (LMV) | Velocity-Position-Position (VLM)
9 | - | need transposing the convolved data before writing to the file | + | correctly ordered, convolved data can be written as is
10 | + | the cube can easily be extended by block of velocities, in particular it may not fit in memory | - | the cube can not (reasonably) be extended on disk. If it fits in memory, it can be written in a temporary output buffer, with more memory cost.
11 | + | default ordering in Gildas, efficient for the imaging tools (one image plane is contiguous in the file) | - | not the default in Gildas, many tools do not expect such order
12 | - | need transposing for an efficient per spectrum analysis | + | the order is correct for spectrum-oriented tools like Class or Cube.