[R-sig-eco] Fwd: adehabitatHR and kernelUD problems estimating home range size

[Isabella Mandl]

Dear all, I apologise for this simplistic question - it might be very easy
and straightforward to solve...? (I hope.)

I've been trying to estimate home range size and UD through both the mcp()
and the kernelUD() functions from the package adehabitatHR. I have done
these calculations before, without a problem, but this time there seems to
be a hiccup I can't figure out.

I have fourteen individual animals, each with its own set of GPS points
from which I want to calculate the home range size (and subsequently
overlap). However, the home range size (when computed via getverticeshr,
kernel.area and mcp) comes back as ridiculously small.

Variables measured:
  id         area
1  1 1.095734e-10
2  2 3.917295e-11
3  3 3.956386e-11
4  4 1.176246e-10
5  5 3.675360e-11
6  6 3.402833e-11
...

I've checked the units and this is the size expressed in hectares. The
normal sizes of these home ranges are between 0.5 and 1.5 hectares. If the
same GPS points are plotted in a GIS programme they look fine size-wise,
why does R not calculate them correctly? What am I overlooking/doing wrong?

The data seems to me to be read correctly as a SpatialPointsDataFrame, the
CRS is set correctly, I can plot the points and the outlines. It's just the
sizes that are messed up.

> str(coords)
Formal class 'SpatialPointsDataFrame' [package "sp"] with 5 slots
  ..@ data       :'data.frame':    4423 obs. of  2 variables:
  .. ..$ Individual: Factor w/ 14 levels "1","2","3","4",..: 1 1 1 1 1 1 1
1 1 1 ...
  .. ..$ Season    : Factor w/ 2 levels "DRY","WET": 1 1 1 1 1 1 1 1 1 1 ...
  ..@ coords.nrs : int [1:2] 4 3
  ..@ coords     : num [1:4423, 1:2] 47.8 47.8 47.8 47.8 47.8 ...
  .. ..- attr(*, "dimnames")=List of 2
  .. .. ..$ : NULL
  .. .. ..$ : chr [1:2] "Easting" "Southing"
  ..@ bbox       : num [1:2, 1:2] 47.8 -14.4 47.8 -14.4
  .. ..- attr(*, "dimnames")=List of 2
  .. .. ..$ : chr [1:2] "Easting" "Southing"
  .. .. ..$ : chr [1:2] "min" "max"
  ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slot
  .. .. ..@ projargs: chr "+init=EPSG:32638 +proj=utm +zone=38 +datum=WGS84
+units=m +no_defs +ellps=WGS84 +towgs84=0,0,0"

Maybe one of you had a similar issue and can point something out to me?
Thankful for any help!
Isabella

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