various questions about GSTAT

[Daniele Iannuzzo]

Good morning to all. I'm an italian biologist. With my research group, we are trying to analyze wildlife population density variations using cokriging maps, and we used GSTAT for this. But we were not able to solve some problems, so i would be very grateful if someone could help me:   - GSTAT by default uses pseudo-cross-variograms to analyze the spatial continuity between different variables. Is there a way to use even classic cross-variograms, to test if are there important differences between the two algorithms?   - We had problems with 'nugget effect', because often it was so strong to produce trivial maps with spikes at sample locations and values very close to sample mean elsewhere. In 'Multivariate Geostatistics' by Wackernagel, it was suggested to delete the value of the Nugget only in the right hand side matrix of the kriging system. Is there a simple way to do this with GSTAT?   - Is there a command to use cokriging with only one unbias condition, instead of classical cokriging with the sum of weights of correlates = 0 ?   Thank you in advance, best regards! Daniele.