Hi Peter, You might want to check out the VSP program....it may help answer your question...
http://dqo.pnl.gov/ Cheers, Greg Hellyer, Environmental Scientist USEPA - New England Regional Lab Ecosystem Assessment - Ecological Monitoring Team (ECA) 11 Technology Drive North Chelmsford, MA 01863 www.epa.gov/region1/lab [EMAIL PROTECTED] 617-918-8677 617-918-8577 (Fax) Peter Bossew <[EMAIL PROTECTED] flex.at> To Sent by: [email protected] owner-ai-geostat cc [EMAIL PROTECTED] Subject AI-GEOSTATS: Sampling problem 08/16/2006 12:03 PM Please respond to Peter Bossew <[EMAIL PROTECTED] flex.at> Dear list: I have the following sampling problem. Given a rectangular regular grid of c columns and r rows (say 10*10), consisting of c*r cells of equal size. I want to chose n cells (say 15 out of 100 cells), which can be interpreted as samples with support equalling the size of one cell, taken from a regular grid of grid distance = cell size. According to which pattern do I have to pick the samples (i.e. which cells do I have to chose) in order to get a frequency distribution of distances between the centres of the cells (n*(n-1)/2 distances = pairs of cells = 105 in the example) which is as close as possible to uniform, i.e. all distances occur with about the same probability ? I tried to solve it numerically, which results in quite strange looking sampling patterns. Trying all combinations (r*c over n = 2.53E17 in the example, if I calculated correctly), is obviously tedious if r,c and n become large. Are there any analytical solutions ? Any literature about this ? Thanks for hints, Peter ----------------------------------------------------- Peter Bossew European Commission (EC) Joint Research Centre (JRC) Institute for Environment and Sustainability (IES) TP 441, Via Fermi 1 21020 Ispra (VA) ITALY Tel. +39 0332 78 9109 Fax. +39 0332 78 5466 Email: [EMAIL PROTECTED] WWW: http://rem.jrc.cec.eu.int "The views expressed are purely those of the writer and may not in any circumstances be regarded as stating an official position of the European Commission." + + To post a message to the list, send it to [email protected] + To unsubscribe, send email to majordomo@ jrc.it with no subject and "unsubscribe ai-geostats" in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list + As a general service to list users, please remember to post a summary of any useful responses to your questions. + Support to the forum can be found at http://www.ai-geostats.org/ + + To post a message to the list, send it to [email protected] + To unsubscribe, send email to majordomo@ jrc.it with no subject and "unsubscribe ai-geostats" in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list + As a general service to list users, please remember to post a summary of any useful responses to your questions. + Support to the forum can be found at http://www.ai-geostats.org/
