SP3 files provide satellite positions for every 15 minutes. How would you find the satellite position at a time between two logged positions, i.e. 7 minutes after the last logged position?
I can think of several ways to do this: 1. Just use the position at the closest interval. 2. Linear interpolation between the intervals on either side. 3. passing a polynomial through several consecutive points and using the polynomial to estimate any satellite position within the time frame.
I don't think the overall effect on the accuracy of the estimates would vary much between all three of these (but I don't know this as a fact). Is this the case? Is there a "standard" way for dealing with it?