Hi Philippe
Why not simply calculating some statistitics of
your points clous before and after the build up of the facilities?
For example I'll try to see if the mean center
and the spread of the cloud changed. Then I guess that more than
considering the single points it could be
interesting to analyze the whole single routes of
the animals and see if something
changed (variability, mean length, ...).
Another simple try could be to calculate a raster
indicating the distance from the coast and make a plot
indicating the number (or frequency) of points
versus the classes of distances and see how it changed.
But probably you already considered these ideas.
Bye
Sebas
At 07.33 05/05/2010, you wrote:
Dear list,
I am working on a project which aims to
determine whether the construction of industrial
facilities near to / in the middle of a
migratory path for large marine animals has an
effect on the spatial distribution of those
migrating animals. My dataset consists of a
series of points marking the location (GPS
coordinates) of animals sighted during several
dedicated aerial surveys over the area (before
and after the construction of the industrial
platform), and I also know the position of the
facilities of course. How can relate the spatial
distribution of animals to the presence of the
industrial facilities, with the objective of
testing whether the animals have been displaced from their normal route ?
My initial thoughts on this were to:
1) test for CSR (Complete Spatial Randomness) in
the point pattern - if the animals were
distributed randomly over the area prior to the
implantation of the facilities but now display a
clustered or gradient pattern in distribution,
this could be indicative of a possible displacement.
2) Construct 2D kernel density estimates, using
appropriate functions in R, for each day an
aerial survey was carried out - that would
enable me to understand how the distribution of animals changes through time.ยจ
Is this the right way to go ? Are there other
tools / analyses out there that may be more
suited to answering my question and that I may not be aware of ?
Any ideas or suggestions much welcome and greatly appreciated,
Many thanks in advance,
Philippe
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