Re: AI-GEOSTATS: Choosing Lag Distance and Angular Tolerance

2001-05-15 Thread Isobel Clark
--- Lucie Vallée <[EMAIL PROTECTED]> wrote: > > > Could you explain what you mean by "nearest > neighbour distances between samples locations"? This is something I learned about in quantitative ecology in the 1960's ;-) You take each sample in turn and find the sample closest to it. Note the d

AI-GEOSTATS: Re: failure delivery

2001-05-15 Thread Isobel Clark
Lucie, sorry I got this message when I tried to reply to your e-mail. Hope you got the generic mailout. > <[EMAIL PROTECTED]>: > Connected to 192.77.51.5 but sender was rejected. > Remote host said: 571 > This domain is banned. Isobel ___

Re: AI-GEOSTATS: Number of data points & Variograms

2001-05-15 Thread Isobel Clark
> My research is on heavy metal pollution in water > bodies. Hi, some thoughts (your numbering): (1) One of the things I have found successful is the following: construct your semi-variogram using ALL of your data but not allowing pairs between samples in different water bodies;

AI-GEOSTATS: Number of data points & Variograms

2001-05-15 Thread K. Ramanitharan
Dear AI-GEOSTATiSticians, My research is on heavy metal pollution in water bodies. As a part of the analysis, I am doing kriging with the pollutant data. I have couple of problems in doing this task. 1. Though I have the data sets for 90 water bodies, most of them (85) have data points less tha

Re: AI-GEOSTATS: Choosing Lag Distance and Angular Tolerance

2001-05-15 Thread Isobel Clark
Andrew You can apply 'standard' geostatistics if the measurements are the 'average' (or some similar feature) over an area. It makes interpeting the semi-variogram extremely tricky if you combine many different sizes of sample, but common sense is the main thing here. The trick is to derive a p

Re: AI-GEOSTATS: Choosing Lag Distance and Angular Tolerance

2001-05-15 Thread Andrew Mullens
I have a question relating to this question, certainly not to question the previous writer, it just seems like a good time to bring it up. Will variograming and other such techniques work for the data the previous writer described, e.g samples aren't at points, but areas (and areas that might have

Re: AI-GEOSTATS: The Estimation of Range paramter is very very big

2001-05-15 Thread Isobel Clark
Are you using some kind of automated fitting? The results would suggest that the model is inappropriate or that your basic assumptions are inappropriate. You should look at how the models are being fitted and what assumptions are made and question everything. Isobel Clark __

Re: AI-GEOSTATS: Choosing Lag Distance and Angular Tolerance

2001-05-15 Thread Isobel Clark
Think of it as focussing a camera. You are looking for the clearest picture. There will be a certain lag (in each direction) at which the calculation will balance between detail on distance, detail on angles and number of pairs. In general: # the more anisotropic the structure, the smaller the t

AI-GEOSTATS: The Estimation of Range paramter is very very big

2001-05-15 Thread Yadollah Waghei
Hello dears I have a spatial data set containing n=262 observations (The variable of interest is Rate of Tuberculosis in 262 counties of Iran). I have fitted exponential variogram model to Empirical Directional Variogram, and I observed that the Estimated Range in some directions is very very

AI-GEOSTATS: Choosing Lag Distance and Angular Tolerance

2001-05-15 Thread Yadollah Waghei
Hello dears I have a spatial data set contaning n=262 observarion (The variable of interest is Rate of Tuberculosis in 262 counties of Iran). I want to fit some models to Directional semi-variograms,and then build anisotropic semi-variogram. Then questions are - Is there any rule for choosing L