Re: AI-GEOSTATS: Kriging Error vs variance
Russell, If you have time to get to your library there is a book "Geostatistical Ore Reserve Estimation" 1977 M.David although related to geostatistics for mining this book is written by a renowned geostatistician and has an excellent diagrammatic representation of trend, drift and stationarity Fig. 188, 189 pp267 which relates to your question. Hope this is of some help. Thanks, Regards Digby Millikan B.Eng Geolite Mining Systems U4/16 First Ave., Payneham South SA 5070 Australia. Ph: +61 8 84312974 [EMAIL PROTECTED] http://www.users.on.net/digbym -- * 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
Re: AI-GEOSTATS: Kriging Error vs variance
You may have to consider the stationarity of your data, i.e. theoretically your sample mean is better than your kriged estimate if your kriginng error is greater than your kriging variance, but you did make the assumption that your data is stationary when you kriged it, i.e. constant mean and variance, if this is not the case then you should consider this when adopting your sample mean. Regards Digby Millikan B.Eng Geolite Mining Systems U4/16 First Ave., Payneham South SA 5070 Australia. Ph: +61 8 84312974 [EMAIL PROTECTED] http://www.users.on.net/digbym -- * 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
Re: AI-GEOSTATS: Kriging Error vs variance
Hi Russell, I am assuming you refer to kriging error variance. If your semivariogram is bounded and has a sill close to the sample variance, then the simple kriging estimate will automatically be the global mean when the kriging variance is the sample variance (that is when all observations are beyond the range of spatial correlation). Note that you might want to decluster your sample mean before using it as global mean. For ordinary kriging, the kriging variance would actually be greater than the sample variance because of the Lagrangian parameter. I don't think I would adopt a global/sample mean instead of the local mean provided by ordinary kriging even if the variance of the estimator is smaller. However, for kriging with a trend or universal kriging, I wouldn't trust too much the estimate obtained for large kriging variance since the extrapolated trend can be very unrealistic (e.g. negative concentration estimates). Pierre <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><> Dr. Pierre Goovaerts President of PGeostat, LLC Chief Scientist with Biomedware Inc. 710 Ridgemont Lane Ann Arbor, Michigan, 48103-1535, U.S.A. E-mail: [EMAIL PROTECTED] Phone: (734) 668-9900 Fax: (734) 668-7788 http://alumni.engin.umich.edu/~goovaert/ <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><> On Mon, 27 Jan 2003, Russell Barbour wrote: > Dear List members, > I am looking for a reference on interpretation of the Kriging error versus the > sample variance. Am I correct in assumung that in any kriged interpolation > where the Kriging error is greater than the sample varience then the sample > mean would be a better estimate at that location? > > Thanks for your help > > Russell Barbour Ph.D. > Research Associate in Applied Mathematics > Vector Ecology Laboratory > Yale School of Medicine > 60 College St. Rm 600 > New Haven CT. 06520 > TEL: 203 785 3223 > FAX 203 785 3604 > email: [EMAIL PROTECTED] > > > > > -- > * 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 > -- * 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
Re: AI-GEOSTATS: Kriging Error vs variance
Russell Absolutely on the spot. We call this the 'ygiagam' criterion (your guess is as good as mine) ;-) Isobel Clark http://geoecosse.bizland.com/news.html __ Do You Yahoo!? Everything you'll ever need on one web page from News and Sport to Email and Music Charts http://uk.my.yahoo.com -- * 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
AI-GEOSTATS: Kriging Error vs variance
Dear List members, I am looking for a reference on interpretation of the Kriging error versus the sample variance. Am I correct in assumung that in any kriged interpolation where the Kriging error is greater than the sample varience then the sample mean would be a better estimate at that location? Thanks for your help Russell Barbour Ph.D. Research Associate in Applied Mathematics Vector Ecology Laboratory Yale School of Medicine 60 College St. Rm 600 New Haven CT. 06520 TEL: 203 785 3223 FAX 203 785 3604 email: [EMAIL PROTECTED] -- * 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
