Re: [ai-geostats] Frightened of Spatial Autocorrelation
- Hi Kevin,
I work in the field of distribution modeling of birds and somewhat come from
the other direction than most geostatistics people here on the list. In
ecology, we first only predicted by local conditions and habitat, then were
pointed to the problems of spatial autocorrelation in such an approach, then
tried to compensate for autocorrelation problems in statistics and only
lately recognized that autocorrelation is actually additional information
that could improve prediction. Steve already posted the most current papers
regarding this issue in Ecography, which helped me much
(http://www.nceas.ucsb.edu/~liebhold/ecography/). I would add the following
paper to the list:
Lichstein J. W., T. R. Simons, S. A. Shriner, and K. E. Franzreb. 2002.
Spatial autocorrelation and autoregressive models in ecology. Ecological
For birds it has been well documented that autocorrelation in distributions
are caused by autocorrelation in underlying resources. Thus, in theory, if
you cover ALL important predictors in your model (let's say a regular
regression or any other "non-spatial" method), the spatial structure in the
distribution is modeled implicitly by being contained in the predictors.
However, if you miss a predictor (which in practice will always be the
case), you will miss its spatial structure and the residuals of your
analysis will reflect this structure rendering these approaches ineffective
and statistically flawed. In addition, I'm trying to show in my research
that dispersal of individuals (meaning leaving either the birthplace or the
last breeding place permanently to breed elsewhere) also leads to
autocorrelation in distributions. This could also be the case for
archeological sites as there was undoubtedly some contact and exchange among
neighbors and this contact would have been more intense with close neighbors
as travel comes at a cost. Thus I would expect autocorrelation in the
spatial distribution of archeological sites above and beyond the
autocorrelation in the underlying conditions predicting archeological sites.
I use conditional autoregressive regression models (CAR) in Splus to model
I hope this helps
Dept. of Wildlife Ecology - Rm. 210
University of Maine
5755 Nutting Hall
Tel. (207) 581 2799
Fax: (207) 581 2858
----- Original Message -----
From: Kevin M. Curtin
Sent: Thursday, September 02, 2004 15:43
Subject: [ai-geostats] Frightened of Spatial Autocorrelation
I'm not sure if this is the correct forum for this.but a colleague has asked
a question I'd like to address.
This fellow wants to predict the location of archaeological sites based on
factors such as soil type, proximity to a water source, slope, AND proximity
to other archaeological sites.
On proposing such a predictive model he has been challenged with, "How are
you going to deal with Spatial Autocorrelation". We're not sure why SA
should be a problem since we are suggesting that spatial proximity is a
factor in settlement location.
So, do we need to test for SA and why?
Thanks in advance,
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