# Need help on SGS parameters

Hi everyone,
I have questions on Sequential Guassion Simulation parameters which confuse me. For SGS, the input parameters include nugget, contribution, ranges (max,med,min) and angles. I want to know how to connect the ranges to the three correlation length (lamda_x, lamda_y, lamda_z). Whether the range_max is three times of the Lamda_x, the range_med is three times of the Lamda_y, and the range_min is three times of Lamda_z. Am I right? Is the contribution is usually one for the unconditional data? The mean and variance are zero and one. If I want to get the stochastic field with mean of 10 and variance of 0.1, I should convert the output data and calculate them from standard normal distribution to normal distribution. Am I right? Thanks. I appreciate it very much!
Fang

..

So the exponential variogram the equation we use is:

g(h) = 1 - exp(-3h/a)

where a is the range.

For sgsim we usually assume that you want to simulate a field with zero mean and unit variance. In that case the sum of the contribution from the variograms models should be one. If you want a field with variance V then the sum of the contribution should be V. You will have to add a constant for a non-zero mean. This is ineficient to simulate Gaussian process but sgsim is usually (and I mean pretty much always) used in conjunction with the normal score transform that change the data distribution into a N(0,1) back and forth.

Hope that helps.