Dear Mr. Silva, I think your problem with (un)expected results for different interpolation methods is not so rare. I had similar problem with (too) small differences between IDW and Kriging/Cokriging solutions. If you are interested about it you can find question and answers stored in ai-geostats mailing list in archive 11/2002 (group.yahoo.com/group/new_ai_geostats/ - question in mail no.756, complete answers in mail no. 761).
Maybe only could add from my experience that Cokriging can be sometimes replaced with Kriging with External Drift. Of course carefully, because as I understood in theory of Cokriging secondary variable describes behaviour of primary, and in KED secondary variable has influence on primary. But, this mailing list includes many experts with much more experience and knowledge then I have and probably you will find more useful information in ai-geostats mailing archives. Best regards, Tomislav Malvic ------------------------------------ MSc. Tomislav Malvic, Grad. Eng. of Geol. INA-Industry of Oil plc. (Naftaplin) Subiceva 29, 10000 Zagreb, CROATIA ----- Original Message ----- From: Alvaro Silva To: [EMAIL PROTECTED] Sent: Tuesday, January 14, 2003 1:02 PM Subject: AI-GEOSTATS: Cokriging Dear all, I'm comparing some different methods in temperature estimation, i.e. idw, spline, ordinary and universal kriging and cokriging. I'm doing it in geostatistical analyst (ARCVIEW 8.1), nevertheless the low errors (by x-val) presented by all the methods, some give better results. The universal cokriging (covariable altitude) is the one with low errors and r nearest to 1, but the map is very close to the other methods's maps. It doesn't reveal the conexion with altitude like it should (the regression coeficcient between temperature and altitude is high 0.88). The DEM has 1km resolution, but the cokriging's map is smooth like the ones from other methods. What can be wrong? I have already reduced the search elypse in the variable altitude to the minimum and the points to include also (so i'm doing something like colocalized cokriging), but the map doesn't reveal much spacial variability. Thanks for your attention �lvaro Jos� �lvaro Mendes Pimp�o Alves Silva Ge�grafo - T�cnico de SIG Geographer - GIS Technician Departamento de Clima e Ambiente Atmosf�rico Climate Department Instituto de Meteorologia Portuguese Meteorological Institute Rua C do Aeroporto 1749 - 047 Lisboa Portugal Tel: (+351) 218483961 Fax: (+351) 218402370 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
