The "maximum" pyramid level occurs when the pixels used in the level 0 image are contained by
one tile in the pyramid. Depending on the origin and dimensions of the image, there may actually
be several tiles, and the AUTO pyramind option doesn't always generate a true "maximum". You
could go higher than the maximum, but there's little computational benefit to doing so.
You can't control the scale of ArcSDE pyramid levels (it's based on a series which doubles the
pixel size). The renderer is likely to do futher interpolation to the image data to convert raster
pixels to screen units anyway.
You might chose a lower level if the imagery was configured to be scale dependent, and you
knew the tiles would never be used, but the storage savings this represents is usually trivial --
stopping at the fourth level (vice letting it go to 7 levels) only saves (1/1024 + 1/4096 + 1/16384)
of the base level storage (roughly - compression efficiency changes by level depending on the
interpolation algorithm). Level selection by scale is dependent on the extent of the image, the
tile size, and the pixel dimensions. I'd only choose a level explicitly if I had a custom 'C' app
which was processing the data, or if AUTO chose a level which was impacting performance
by being too small.
The documentation does a good job of showing the details of how the pyramid construction
process works.
- V
