error in trmesh (alphahull package)

Hello R community,

I have cross-posted with r-sig-geo as this issue could fall under 
either interest group I believe.
I just came accross the alphahull package and am very pleased I may 
not need to use CGAL anymore for this purpose.   However, I am having 
a problem computing alpha shapes with my point data, and it seems to 
have to do with the spatial configuration of my points (which form 
long, skinny, contiguous clusters).  If I use rnorm to generate the 
same sample size with the same mean and SD, I can compute the alpha 
shape without trouble (which is why I think it might have to do with 
the spatial arrangement of my points).  See below:

# first here's a quick sample of my data (UTM coordinates)

xcoords[1:5]

[1] 670080.2 670080.2 670080.2 670080.2 670080.2

ycoords[1:5]

[1] 5005501 5005499 5005498 5005497 5005495

xcoords[1:5]

#try the ashape routine with error

alpha.shape<-ashape(xcoords,ycoords,15)

Error in tri.mesh(X) : error in trmesh

#get statistics to generate a similar dataset to test against

length(xcoords)

[1] 26257

length(ycoords)

[1] 26257

mean(xcoords)

[1] 670462.4

mean(ycoords)

[1] 5005382

sd(xcoords)

[1] 149.3114

sd(ycoords)

[1] 181.5950

#generate the test data

xtest<-rnorm(26257,670462.4,149.3)
ytest<-rnorm(26257,5005382,181.60)

# try ashape routine with success

alpha.shape<-ashape(xtest,ytest,15)
class(alpha.shape)

[1] "ashape"

Thanks for any insight into this!

Murray

ps I am able to compute the alpha shapes for this same dataset without 
problem using CGAL but I find it a pain to work with....