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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)
[ATTACH=CONFIG]33016[/ATTACH]

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)
[ATTACH=CONFIG]33017[/ATTACH]

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
[ATTACH=CONFIG]33018[/ATTACH]

For Day2
[ATTACH=CONFIG]33019[/ATTACH]

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...

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