Make sure that you have the set up as described here
http://www.mtbest.net/setting-up-navi-GT31.htm

Setting up GT31 manually

1. MEMORY CARD
a. LOG SWITCH should be ON-FIX. There is no point to log any data when there is no position fix.
b. NMEA ITEMS should be set to "SBN 1 SEC". Binary logging ensures maximum possible trackpoint accuracy and maximum data reliability. If you want the most complete data set from your sailing session, use SBN (binary) format logging.
c. MIN SPEED should be set somewhere between 2 and 5, unless you are specifically interested to log data when you are stationary.
d. FORMAT CARD. Read readme.txt file to find which cards are compatible with G31. Format the card a few times in a row. If you succeed each time, you can rely on the SD card that you use. Formating is the most drastic writing operation you can perform on your card and hence it is the ultimate test of your SD card compatibility.
e. FILE SIZE should be set to CARD SIZE. This means that you do not put any limit on file size.

Have you set the time zone correctly? If not then it may make a new file as you go past 0:00 GMT.

Also what is the file size of the first file?

It may be the file size it was set to 1024 which is the max size of the session it used to record, i've tried to set it 2048, hopfully this works?!

wantmorewind said...

It may be the file size it was set to 1024 which is the max size of the session it used to record, i've tried to set it 2048, hopfully this works?!

I don't believe this, It's been suggested twice already you set it to "card size" what's so hard about that?????

As Neb's says setting it to anything else will cause a new file to be created once you reach whatever you've set.

Edit, woops sorry that was uncalled for, Mr grumpy coming out!

mineral1 said...
Bloody confusing really, and your not the only one to get stuck on this little gem

You're not wrong... took me a while to wrap my head around the NAVI as well. It does take a bit of nutting out, but once you get there, it's easy as pie




... well most of the time!