Hi to the List,

Again - thanks for your help - as you probably guessed I am new to Spatial
Analyst!

Thanks for replies from Chris Duncan, Kris V., Bill Huber, Michael S.
Batcher and Jeff Jenness.

These helpful people directed me towards:

  - converting my polygon SHP file to a GRD (with the numeric label as the
value, but not really needed)
  - using the Analysis->Summarize by zones... options and selecting the
overall grid I wanted to summarize (in this case contoured monthly
precipitation)
  - saving the tables produced as a series of text files (for later
compilation and aggregation in Excel)
  - I could also use a join to get the tables associated with the original
basin polygon theme attribute table

Worked like a charm - thanks guys! (RTFM on my part next time huh?)

Bill pointed me to an excellent tutorial on this (and other things GRDee)
at
http://www.quantdec.com/SYSEN597/GTKAV/section9/chapter_29c.htm#summarize

Kris and Jeff suggested I could automate the process using Avenue and
ZonalMean  / ZonalStatsTable - sounds like a good reason to get my feet wet
in Avenue scripting...

Regards & Thanks Again All:
GREG...

"Ahhhh.... ArcView, the idiot savant of the GIS world...."




------------------------------------------
Greg Cocks wrote:

> Hi,
>
> Suggestions please - will sum of course:
>
> 1) I have a series of basins as polygons within one SHP theme.
> 2) I have created interpolated grids of monthly precipitation across
> (and beyond) these basins for a number of months
> 3) I would like to get the average monthly precipitation (i.e., the
> average cell value) inside each polygon - and then update the attributes
> table for the SHP file of the basins with this average value
>
> I could clip each GRD, polygon by polygon, month by month, and work it
> out that way but that would take awhile as you could imagine..
>
> Thanks in advance.....
>
> Regards,
> GREG...