[Therion] Multiple fixes for the same point

I'm sure that this has been covered, but I cannot find it anywhere. I have 3 different gps results for a surface point, all taken with the same gps but on different days, so rather then picking one I just used fix on all 3. However, therion appears to be taking only the last one I enter. This does not seem to be the right behaviour! Is there a way for Therion to take all 3 and 'average' them? thanks in advance Andrew