Jonathon
I've been wanting to explore the IKONOS dataset for a while now. Did you
get hold of data at a reasonable cost?
Phil
At 03:34 PM 5/5/04, you wrote:
>Remote Sensors:
>
> Me and a colleague (who shall remain unnamed... We will refer to him as
>Solomon D.) are having a lively discussion about training/test data with
>remote sensing and I was hoping to get some additional feedback on this
>problem. We created a species map with maximum likelihood (using 1m IKONOS
>imagery), and here's how we created training data (and how we are
>approaching, in one case, the testing):
>
> We have mostly USFS plot data with a known center location and plot
>boundary, and that has cover values for each species we are after in our
>classification. We choose pixels from plots with a high percentage of a
>single species, that are readily identifiable as the species in question
>(e.g. If we know a plot only contains red fir trees, we manually choose each
>pixel belonging to a tree within the boundary of the plots). This, of
>course, is not an optimal way of doing this -- in theory we should have
>collected individual species in the field, but this was our curse with the
>data we had.
>
> Ok, so now we have a bunch of pixels per class, taken from a limited
>number of plots (e.g. We may have 1000 red fir pixels, but we took them from
>10 plots). The questions is, is it "legitimate" to subdivide the 1000
>pixels into two randomly chosen training and test groups (say 60% train and
>40% test), and use the 60% to create the map, and validate it with the
>remaining 40%, OR do we have a problem with spatial autocorrelation problem
>because, while we have 1000s of pixels, the training and test pixels are all
>right next to each other in the 10 plots.
>
> In my mind the issue is muddled, because we are training based on color,
>and is does the color (within a class) have a strong enough spatial pattern
>to warrant a very different training/test setup (e.g. Taking the pixels from
>6/10 plots for training and 4/10 for testing?) Thoughts?
>
>--j
>
>--
>Jonathan Greenberg
>Graduate Group in Ecology, U.C. Davis
>http://www.cstars.ucdavis.edu/~jongreen
>http://www.cstars.ucdavis.edu
>AIM: jgrn307 or jgrn3007
>MSN: jgrn307@msn.com or jgrn3007@msn.com
_________________________________________
M. Philip Nott, Ph.D.
Research Ecologist
The Institute for Bird Populations
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email: pnott@birdpop.org
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