# Calculating MODIS 8-day composite GPP product as yearly [closed]

I want to use MODIS GPP 8-day composite product for an annual time series analysis.

How to calculate the annual GPP from the 8-day composite? Since the fractions represent the daily average rates of GPP for an 8-day period, do I multiply the sum of 8-day composite fractions of GPP by 8?

## closed as too broad by ahmadhanb, whyzar, user30184, Vince, BBG_GISApr 5 at 17:06

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• Add up all the 8-day composite values for a year, and divide by the total number of 8-day periods in that year (which might be 365/8 = 45.625, or it might be rounded up or down, or some other solution - you need to read the metadata to figure this out). Be sure to find out if any of the 8-day periods overlap, because that would invalidate your results. – csk Apr 5 at 18:06