I realy don't see any need to save every part of the sentences unless
you have to play them back into PC mapping software to trick it into
thinking it's connected to a GPS.

Even if the whole sentence needs to be reproduced, the pic program could
put the correct data into a blank sentence itself on playback, so that '$GPRMC' didn't need to be saved a million times.

You need to read the entire sentence in if you want to check the checksum,
but lots of data can be discarded straight after that.

Playing the data from the device you make into the PC as if it was produced
live by a GPS is one way to transfer files to a PC no matter what media the data is stored.

I am using 16 bytes per entry that includes lat,long,time, valid/invalid,
and must soon include at least part of the date.
one 16 byte entry per second gives 34 min and 10 seconds logging on a
24LC256 EEPROM, and it is easy to connect 8 of them to two wires.

It is good if your pic program can set up the GPS antenna from scratch,
since some of them can 'forget' what they are supposed to be doing.
Also, it would make it possible to connect a new GPS straight to the pic
without using a PC to configure it.
Art.