Annelies I hope I do not offend anyone on the list by answering this question. Anyone who does not have the book can download it free of charge from http://uk.geocities.com/drisobelclark/practica.htm
Chapter 4 is dedicated to explaining the concept of the estimation variance. In the 'old days' when this book was written, it was felt to be simpler to use examples where all samples were weighted equally to get over the concepts of calculating the "extension variance". Only when this was established did we introduce the concept of different weights for each sample. This, then, leads to the development of kriging. You will find this approach in all of the early textbooks and course notes. In Practical Geostatistics, Chapter 5 starts "Let us turn, now, to a much more common, and probably more realistic, approach to the estimation............" I admit that Chapter 5 is very brief, but if you take the terms calculated in all of the examples in Chapter 4, you can arrange them in the kriging system and se what weights the samples should have. You will then see that the 'optimal' weighting will be different for different length samples. Isobel http://geoecosse.bizland.com/seasonsgreetings.htm --- Annelies Govaerts <[EMAIL PROTECTED]> wrote: > I have a question about an excercise I found in > "Practical > geostatistics" (Isobel Clark). > In chapter 4 they look at the estimation variance of > some, theoretical, > examples. > One of the examples is a 2D panel (30m at 40m). They > use the average > grade of two drives, (one along the side of 30 m en > one along the side > of 40m) to estimate the value inside the panel. (for > those who has a > texbook the excercise is on pages 80-84). > > I found it a bit strange to use samples with > different lengths? And why > doesn't they get different weights in the formula > for the estimation > variance? > So even when you have a more extreme case where you > have a 1m by 40 m > panel you should not taking in account this > difference in length of the > two drives? > > Thanks, > Annelies > > > > * By using the ai-geostats mailing list you agree to > follow its rules > ( see > http://www.ai-geostats.org/help_ai-geostats.htm ) > > * To unsubscribe to ai-geostats, send the following > in the subject or in the body (plain text format) of > an email message to [EMAIL PROTECTED] > > Signoff ai-geostats
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