If you calculate Thiessen polygons for your 6 gauges and clip them to your grid cell boundary then you'll be able to see how much each gauge would contribute to the interpolated mean grid cell value. So you can just use the areas of the polygons as weights for a weighted mean, and that should come out the same as interpolating and then aggregating. If the position of the gauges doesn't change, then the weights don't change so you only have to do that once. Then you just apply your weighted mean function 730 times.
Does that make sense or did I misunderstand something? On Mon, Aug 15, 2011 at 2:03 AM, Hanlie Pretorius < [email protected]> wrote: > Hi, > > I have rainfall measurements from 6 gauges that I want to interpolate > to an areal value (a 'surface'), so that I can compare the > interpolated gauge values to a satellite rainfall estimate that covers > a grid cell of 28kmx28km. Two of the gauges are outside, but close to > the border of the grid cell. Therefore, I also need to clip the > interpolated surface to the grid cell and to get the average of the > surface value in this clipped surface. > > However, for each rain gauge I have 730 values representing a daily > measurement over two years. As output, I need a text file > with the interpolated rainfall values for each day in my time series. > So, I was wondering if there is an 'easy' way to get my output without > creating 730 GIS layers? > > Regards > Hanlie >
