Looking to the residuals for the different model updates.

It is important to monitor the residuals (reference - predicted) to check the performance of the models all the way untill we find that our model become robust. In this case we start with a LOCAL model for moisture which does not represent quite well the new samples so the residuals are quite large. Some of these samples were added to the LOCAL database developing a new model (UPG1) which was again evaluated with a new test set (new samples), and we continue doing this for 2 more times.

Upgrades 2 and 3 give the result and  the GH value so we can add to every residual point the GH value to check if the sample is an outlier, and we can see that points far apart than the zero line have a high GH value.