Hi Ulrich I'm surprised we got mainly "pragmatic" answers to your question and would have expected from statisticians and mathematicians more reactions about a possible statistical heresy: the semivariogram model is fitted to an experimental semivariogram which was obtained from a certain number of points. To be mathematically correct in terms of the various hypotheses used, should one not use a search neighbourhood that is equal to the one used to obtain the semivariogram (frequently all points) ?
If one tries to obtain maps that are "realistic", I mean here maps created by experts that have some additional knowledge about the investigated phenomenon, one would most probably try to get rid of various problems that can be solved by reducing the search radius or the number of neighbours . Pierre's reference to the impact of the relative nugget effect on points that are located far away is often a decisive one. On the other hand, if the main objective is to compare various algorithms (e.g. ordinary kriging versus indicator kriging, or indicator kriging versus log-kriging) or kriging variances obtained by various models, I would imagine that using a "no search" approach (all neighbours are used) would be the most reasonable approach... Just a few thoughts. Gregoire Ulrich Leopold <[EMAIL PROTECTED]> wrote: > Dear list, > > What would you consider the most reliable ordinary kriging estimate? To > use a local search neighbourhood (slightly bigger than the effective > range) or set to global to include *all* data locations? > > > Ulrich > > > -- > __________________________________________________ > > Ulrich Leopold MSc. > > Department of Physical Geography > Institute for Biodiversity and Ecosystem Dynamics > Faculty of Science > University of Amsterdam > Nieuwe Achtergracht 166 > NL-1018WV Amsterdam > > Phone: +31-(0)20-525-7456 (7451 Secretary) > Fax: +31-(0)20-525-7431 > Email: [EMAIL PROTECTED] > http://www.frw.uva.nl/soil/Welcome.html > > Check us also out at: > Netherlands Centre for Geo-ecological Research > http://www.frw.uva.nl/icg > > > > > -- > * 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
