Dear Shaenandhoa,
an obvious coordinate shift is a data error, and you should correct it
before doing any analysis.
A systematic shift of 100-200m in most cases is due to differences in
coordinate systems or coordinate transformations; or due to the way
specific software handles coordinates.
However, to investigate the cause of your coordinate shift, one would
need to see the data and your previous processing steps.
Hope this helps
Karl Hennermann
IT Officer - Spatial Data Research
School of Environment and Development
The University of Manchester
Tel: +44(0)161 275 3655
Quoting Shaenandhoa García Rangel <[log in to unmask]>:
> Dear members of the list,
>
> I am writing to seek advice regarding minimum mapping units (MMU)
> and the geographic fit of different data sources. Currently, I am
> working on a habitat availability map that I develop for my study
> site )Sierra de Portuguesa - Venezuela Andes), based on the needs of
> the Andean bear (/Tremarctos ornatus/). I chose a MMU of 1hectare
> for the output and the Kappa analysis yield 69% accuracy for the
> overall map and 82% for Andean bear habitat. Using this map I have
> estimated area for habitat available, an evaluated the effects of
> different edge depths and fragmentation scenarios.
>
> I would now like to run an analysis to evaluate factors involved on
> habitat prevalence such as rivers, roads, distance to villages etc.
> The issue I have here is that the shift between the satellite images
> and the topographic maps that provide these data is about 100-200m
> and thus the MMU would at most has to be 2 hectares. With this MMU,
> the kappa for the overall map is about 54% and the accuracy for the
> habitat available is reduced as well regarding commission error.
> Thus, I was wondering if I could run these two analysis with
> different MMU, in order to take the full advantage of a higher
> accuracy in the estimation of habitat extent, it would be a shame to
> loose accuracy given possible errors introduced by hard copy maps.
>
> I would really appreciate any advice on this subject,
>
> S
>
> Shaenandhoa García Rangel
> PhD Candidate
> Wildlife Research Group
> University of Cambridge
>
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