[GRASS-user] Entering '<1' and 'BDL' in Database

[Rich Shepard]

On Mon, 19 Apr 2010, Dylan Beaudette wrote:

> how about NULL ?

Dylan,

   NULL means unknown, and 'less than 1' or 'below detection limits' means it
cannot be measured with the instruments used. There's a big difference. NULL
can result from the measurement not being taken or the analysis not being
conducted.

Thanks,

Rich