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Semivariogram Analysis

Question asked by taejnkwon on Apr 10, 2014
Latest reply on Apr 11, 2014 by taejnkwon
I am trying to use semivariogram to analyse/characterize the spatial patterns of friction measurements collected at an equal interval (every minute) by a mobile unit. The measurements are GPS tagged so they can be visualized on the map as attached below. (the lines represent a road network)

I am trying to build a semivarogram model for each run (collected at different days) and compare their similarities/differences by examining the model parameters (i.e., sill, nugget, range..)

Here I have attached the diagram of datasets collected at two different days (Excel file is also attached)

As you can see, the friction measurements collected on these two days are similar to each other and thus I would expect that their spatial patterns are also similar... But their semivariograms show that they are quite different to each other..

For Day1

For Day2

Would anyone be able to reason why this is the case? I would expect that, for instance, their ranges should be similar but they aren't. I understand that the range (and other parameters) could vary subject to how one fits the empirical semivarainces by using different models (gaussian, exponential...etc), but there still exists a large difference in their spatial characteristics.

Any comments/suggestions would be appreciated...