What are the formulas used in SAGA Ordinary Kriging?

Question

can some one name the formulas avaible in the Ordinary Kriging Modul of SAGA:

What ist the exponential, spherical, Gaussian-Model, etc.?

Answer 1

Linear Regression:

• a + b * x
• a + b * x + c * x^2
• a + b * x + c * x^2 + d * x^3
• a + b * x + c * x^2 + d * x^3 + e * x^4

Logarithmic Model:

• a + b * ln(x)

Power Model:

• a + b * x^c

Gaussian Model:

• a + b * (1 – exp(-(x /b)^2))

Spherical Model:

• a + b * ifelse(x > c, 1, 1.5 * x / c - 0.5 * x^3 / c^3)

I don't know a + b * sqrt(x).