[R-sig-Geo] variogram question

[Wesley Roberts]

Dear r-sig-geo users,

I am currently analyzing some Lidar data we have collected over our study area. I am interested in identifying the range of the semi-variogram as this value will determine the width of pseudo-flight lines I intend to use to sample the lidar data. Our point density is upwards of 5 points per square meter captured over even-aged managed Eucalyptus plantations with an espacement of 2 meters between trees and 3 meters between rows. 

I have imported an x,y,z data set containing canopy height and coordinates and successfully run the experimental variogram using the "variogram" module in gstat. 

cpy.pts2 <- variogram(dbl_5 ~ 1, cutoff=50, width=2, D)

I have also managed to fit several models using the 

cpy.pts2.fit <- fit.variogram(cpy.pts2, model = vgm(2, "Sph", 4, 5))

command as suggested by the gstat manual. I would like to fit the various models "Sph, Exp..." etc without having to specify the nugget psill and range. Essentially I would like an objective method to measure and record these values as I will be running several hundred variograms. Is it possible to perform this type of analysis using gstat?

Many thanks for all your help and suggestions
Wesley

Wesley Roberts MSc.
Researcher
Earth Observation (Ecosystems)
Natural Resources and the Environment
CSIR
Tel: +27 (21) 888-2490
Fax: +27 (21) 888-2490

"To know the road ahead, ask those coming back."
- Chinese proverb

-- 
This message is subject to the CSIR's copyright terms and conditions, e-mail legal notice, and implemented Open Document Format (ODF) standard. 
The full disclaimer details can be found at http://www.csir.co.za/disclaimer.html.

This message has been scanned for viruses and dangerous content by MailScanner, 
and is believed to be clean.  MailScanner thanks Transtec Computers for their support.