[Mapserver-users] Just call me a newbie . . . multiple Raster LAYERs question

[Bob Basques]

All,

Let's say I have Six different levels of resolution of Aerial Photo's  
all of them having the same coverage extents.

Can I use different source data (a different tileindex for each of the 
levels above) for different classifications of the LAYER?

Like the following, which is the coursest layer at 16 feet per pixel:

#
# Start of map file
#
MAP
  NAME CITIPIX
  STATUS ON
  SIZE 600 600
  EXTENT 540000 135000 600000 175000
  UNITS FEET
  SHAPEPATH "./data"
  IMAGECOLOR 255 255 255

  IMAGETYPE JPEG

  LAYER
    NAME "AERIALS"
    STATUS DEFAULT
    TILEINDEX "RAST_STPL_PW_AER_SUR_2001_06_L5"
    TILEITEM "Location"
    TYPE RASTER
  END

END # Map File

I have five other TILEINDEXes,

RAST_STPL_PW_AER_SUR_2001_06_L4 = 8 feet per pixel
RAST_STPL_PW_AER_SUR_2001_06_L3 = 4
RAST_STPL_PW_AER_SUR_2001_06_L2 = 2
RAST_STPL_PW_AER_SUR_2001_06_L1 = 1
RAST_STPL_PW_AER_SUR_2001_06_L0 = 0.5

Do I need to make a layer for each tile index, or can they all be 
sourced under the same LAYER definition (aerials)?  There will only ever 
be one of them at a time visible.  So can the layer look like this (or 
some close)?

  LAYER
    NAME "AERIALS"
    STATUS DEFAULT
class [pixel]
classitem  ( [pixel]   >=   16 )   ## what does "pixel" represent 
anyway?  It's not clear to me from the HowTo
    TILEINDEX "RAST_STPL_PW_AER_SUR_2001_06_L5"
classitem  ([pixel} >= 8 )
    TILEINDEX "RAST_STPL_PW_AER_SUR_2001_06_L4"
classitem  ([pixel} >= 4 )
    TILEINDEX "RAST_STPL_PW_AER_SUR_2001_06_L3"
classitem  ([pixel} >= 2 )
    TILEINDEX "RAST_STPL_PW_AER_SUR_2001_06_L2"
classitem  ([pixel} >= 1 )
    TILEINDEX "RAST_STPL_PW_AER_SUR_2001_06_L1"
classitem  ([pixel} >= 0.5 )
    TILEINDEX "RAST_STPL_PW_AER_SUR_2001_06_L0"
    TILEITEM "Location"
    TYPE RASTER
  END


or do I need to class them each as seperate layers in the map file with 
a max/min specification?

Thanks

bobb