Chaosheng This is very true that if you grid a grid of points inside a polygonal area then average them, you get exactly the same answer as if you kriged the polygon average directly.
The differences are two: (1) you have to do at least 64 krigings to get within 1% of the correct average answer (see my paper at the first Geostat Congress in 1975) (2) if you do one kriging for the polygon average, you get the kriging variance for the polygon average. You can derive this from the discretised point kriging variances but you have to do even more work (64 squared) than in (1). Isobel http://geoecosse.bizland.com/whatsnew.htm ___________________________________________________________ Yahoo! Messenger - Communicate instantly..."Ping" your friends today! Download Messenger Now http://uk.messenger.yahoo.com/download/index.html -- * To post a message to the list, send it to [EMAIL PROTECTED] * As a general service to the users, please remember to post a summary of any useful responses to your questions. * To unsubscribe, send an email to [EMAIL PROTECTED] with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list * Support to the list is provided at http://www.ai-geostats.org
