what does the system do if the admin doesnt set a value for that
dataset?
ncWMS scans each dataset when it's first loaded into the system and
makes a test extraction of a chunk of data from the first timestep and
first z level from each variable. Then it finds the min and max of this
data subset, adding 10% at top and bottom. It's far from perfect but it
at least gives a reasonable guess, which the sysadmin can override if it
turns out to be a bad choice.
If that doesn't work for any reason, ncWMS applies the default range
[-50:50]. But this doesn't happen very often.
The estimated scale ranges are persisted to the ncWMS config file so
they don't have to be recalculated when the server is rebooted.
I guess this approach would be difficult to apply in TDS, where the data
catalogs could be very big.
Jon