Sigrun Calculating of cross semi-variograms has to be done on residuals if there is a trend, just like any single variable semi-variogram. You might find our MUCK papers useful, as we were co-kriging two variables both with trend back when we first started in the 1980s. You can find our papers at http://uk.geocities.com/drisobelclark/resume/Publications.html (note the capital P).
Your other question about search radii. When trend is present, you need to enlarge your search radius past the range of influence to get enough samples to condition the equations properly - that is, to solve for the trend as well as the weights. You can see how this works with uor kriging game, free to all at http://geoecosse.bizland.com/softwares Hope this helps Isobel [Clark] ________________________________________________________________________ Download Yahoo! Messenger now for a chance to win Live At Knebworth DVDs http://www.yahoo.co.uk/robbiewilliams -- * 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
