I need to calculate the average daily temperature for each month. As an input I have 5 .asc grids for 6, 9, 12, 15, and 18 GMT for each month of the year. I was wondering if there is a predefined tool to calculate the average using polynomial fitting. There is one GRASS module r.fitpoly, however it is not available in the standard version. The information about the GRASS module I had found here: http://www.sciencedirect.com/science/article/pii/S1364815205001593. Could you please give me a hint what else I can use for such procedure?
There is a new GRASS GIS 7 Addon which can reconstruct incomplete time series by calculating the missing data from a harmonic analysis. See
In order to install, use the Addon manager of the graphical user interface or g.extension. The method does not use polynomial fitting but HANTS which is also able to detect outliers.