x y is the same at any location on the chip this is quite different from statistically corrected spatial interpolation methods that break up the coordinate frame into regions of equilateral triangle areas this method does not require the coordinate frame to be separated into many regions also the equations given above allow multiple seed point grid spacings and even arbitrary seed point placement this was not possible with the previous statistically corrected spatial interpolation method that depends on a constant spaced equilateral seed point grid across the coordinate frame chip region to be modeled so with this method and the equations described above the radius of influence may change across a chip area based on influences of the local environment at x y that affect spatial correlation versus distance such as local metal layer density pattern uniformity etc using the equations given and explained above random variables were assigned to the straight line test points locations 48 shown in fig5 a fig5 b show the statistical correlation 54 between the initial test point located at the origin of the x axis 49 in fig5 a and all the other test points along the straight line test point array the statistical correlation data shown.