Just thought I would post what I found setting up my GT-31 for other newbies to this GPS, and for a sanity check from the experts.

The 1st thing I did was to follow Tom Chalkos instructions
http://mtbest.net/setting-up-navi-GT31.htm
I found that you had to have the firmware file in the Updater Program folder otherwise I kept getting a really long error message which essentially meant a read or write error. Updated firmware successfully and followed all other instructions.

I got a 1 gig Sandisk SD card for about $8, and once I got it to lock into the socket, and not just kept in with the compartment door closed, worked fine.

At 1st I could'nt record/download any tracks even though the unit looked like it was working fine, then I found that on the TRACK screen the INTERVAL was set to STOP, so I changed this to 1 SECOND. Tracks now record and download OK. This didn't appear to be covered by any of the instructions.

I also checked other settings on the GPS Team Challange site to make sure I hadn't missed anything
gpsteamchallenge.com.au/guides/setupgt11_2008.php
I changed
- time zone to + 10 AEST which I think is right for Brissy
- date format to what we ozzies use
- position to dd.dddddd
- interface to binary (it was NEMEA)

Reading the data logger with Navilink II was OK, and could convert to GPX, NMEA files etc. with the converter function.
Reading from the SD card generated the files NMEA, GPX, PLT and google earth PLT files straight into a folder dated for that day.

The program CD came with version 1.917 of Realspeed, my old version didn't support doppler so I used this new one.
- I can get realspeed to open the NMEA files fine and all looks OK, but when I open the GPX files most of the data appears as invalid so the results are all wrong. Is this is how its supposed to be ? Or should you be able to use either file types.
- I also found that using the NMEA file converted from the data logger files gave slightly different speeds to NMEA file direct from the SD card, some were higher and some where lower. Is this correct ?
- some instructions say that on the MEMORY CARD to set LOG SWITCH to ON or ON-FIX, I used ON-FIX today, but will use ON next time I sail
- I still need to stick a washer around the joy stick.

Thats about it, tried it today and seemed to work as expected. I used the Paqua midi water proof pack and it worked fine.

Sound OK have I missed anything

Hey Haggar,

Good to see you remembered to do the pack up this time

Also turn your unit on, Go to Memory Card -> NMEA items. Now set SBN to 1 second. This should turn off all the other file formats as well (not sure if the GT31 does this, anyway all you need is the SBN file).

Then you should be good to go

Yep agree with Nebs, you shouldn't have all those different file types on the card, just one .sbn file

And I have my "interface" set to NMEA. not sure what "binary" does, but think NMEA is recommended, for the GT11 anyway.

Good to hear the real world version of how someone finds how it goes. Good points about guides etc. I guess none are perfect but your points should be added to help others avoid pitfalls as well.

The setting 'On-Fix' will only write data points to file when the GPS has a position fix. Tom argues that this is more effecient as it saves writing non valid data. ie. data from when the GPS does not have a proper fix.
The setting 'On' will write data to the memory all the time, fix or no fix. I like to set my GPS up this way so if there are errors from loss of satellites or other reasons I have that data to try to explain why it happened. I don't mind using more memory because there is really no shortage and I have never run out of internal logger space in a day yet. Data that is not valid is rejected in the analysis by the software anyhow.

Time zone in Victoria this time of the year is +11 as we have daylight saving. Don't you have that in Brissy?

Do yourself a favour and completely forget about Navilink. Use the card reader in your laptop to copy the files (.sbn and .sbp) directly to your laptop and read them to RealSpeed from file. This avoids errors and rounding that can occur when file format conversion takes place. If your computer does not have a card reader, you can get one for very little money that will plug into the usb port like these:






PS. The GPS saves the data directly to the card in the .sbn format and to the internal memory buffer in .sbp format. They both have all the essential information at the highest available precision (which can be lost in conversions) but the .sbn data files are slightly larger as they contain some extra information about satellites and positions that can be useful in analysing problems of reception etc. For our purposes there is absolutely no reason to use any other data format unless you need to convert it to maybe .gpx or nmea for use in another program.
At the completion of a session you should go to the 'Data Logger' menu and select 'save to card'. In less than a minute this will save the data to the SD card in the .sbp format. When you read your card you will find both a .sbp file and a .sbn file that contain the same data from your session. There are sometimes other very small files from the same date. These you can ignore as they are junk data made when your have turned on your GPS to copy files across etc if you have the logging set to 'On'.
You can also save the Speed Genie data (Max speeds and Max 10 sec) to the card.
To do this go to the 'Speed' menu and in the 'speed' section press the joystick and select the 'save to card'. This will make a small text file which lists the same data as you see when you select 'Restore' in the Speed Genie.

Hope this helps. :)

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decrepit said...

Yep agree with Nebs, you shouldn't have all those different file types on the card, just one .sbn file

And I have my "interface" set to NMEA. not sure what "binary" does, but think NMEA is recommended, for the GT11 anyway.

Actually no. NMEA is not recommended. There is a limit to the precision saved in the NMEA file (only to a lower number of decimal places) so there is still some grid effect in the trackpoints and not as much precision in the doppler data.
The GPS should be set to Binary. You should then get a .sbn file on the card automatically. This saves the highest precision the unit can provide.
The Data Logger (internal memory) saves to the same precision in a slightly abbreviated file (it does not save some if the things we do not need for speed sailing). You should save this to your card at the end of each session and clear it before you start the new session. This is not strictly necessary but I is more convenient because it means that the .sbp file only contains data from that one session.

Select to expand quote

sailquik said...

decrepit said...

Yep agree with Nebs, you shouldn't have all those different file types on the card, just one .sbn file

And I have my "interface" set to NMEA. not sure what "binary" does, but think NMEA is recommended, for the GT11 anyway.

Actually no. NMEA is not recommended. There is a limit to the precision saved in the NMEA file (only to a lower number of decimal places) so there is still some grid effect in the trackpoints and not as much precision in the doppler data.
The GPS should be set to Binary. You should then get a .sbn file on the card automatically. This saves the highest precision the unit can provide.
The Data Logger (internal memory) saves to the same precision in a slightly abbreviated file (it does not save some if the things we do not need for speed sailing). You should save this to your card at the end of each session and clear it before you start the new session. This is not strictly necessary but I is more convenient because it means that the .sbp file only contains data from that one session.

I think the "interface" part of things refers to what data gets spat out the "serial" port of this unit when it's running normally. This is only an issue when you connect your GPS to a laptop so you can get realtime GPS info (like a moving map display etc). In which case I think NMEA might be more compatible with more programs.

I don't think that the "Interface" has anything to do with the internal card.

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nebbian said...

Hey Haggar,

Good to see you remembered to do the pack up this time

Also turn your unit on, Go to Memory Card -> NMEA items. Now set SBN to 1 second. This should turn off all the other file formats as well (not sure if the GT31 does this, anyway all you need is the SBN file).

Then you should be good to go

Actually the Navi is light and the opening to the Paqua is small, so its never gonna fall out.

I definitely had the NMEA items set to SBN and 1 second. I think I need to get a SD reader and see what is actually on the card.

Select to expand quote

Haggar said...

nebbian said...

Hey Haggar,

Good to see you remembered to do the pack up this time

Also turn your unit on, Go to Memory Card -> NMEA items. Now set SBN to 1 second. This should turn off all the other file formats as well (not sure if the GT31 does this, anyway all you need is the SBN file).

Then you should be good to go

Actually the Navi is light and the opening to the Paqua is small, so its never gonna fall out.

I definitely had the NMEA items set to SBN and 1 second. I think I need to get a SD reader and see what is actually on the card.

Hey Haggar does your printers have a card reader on it.
you can use it

Select to expand quote

nebbian said...

sailquik said...

decrepit said...

Yep agree with Nebs, you shouldn't have all those different file types on the card, just one .sbn file

And I have my "interface" set to NMEA. not sure what "binary" does, but think NMEA is recommended, for the GT11 anyway.

Actually no. NMEA is not recommended. There is a limit to the precision saved in the NMEA file (only to a lower number of decimal places) so there is still some grid effect in the trackpoints and not as much precision in the doppler data.
The GPS should be set to Binary. You should then get a .sbn file on the card automatically. This saves the highest precision the unit can provide.
The Data Logger (internal memory) saves to the same precision in a slightly abbreviated file (it does not save some if the things we do not need for speed sailing). You should save this to your card at the end of each session and clear it before you start the new session. This is not strictly necessary but I is more convenient because it means that the .sbp file only contains data from that one session.

I think the "interface" part of things refers to what data gets spat out the "serial" port of this unit when it's running normally. This is only an issue when you connect your GPS to a laptop so you can get realtime GPS info (like a moving map display etc). In which case I think NMEA might be more compatible with more programs.

I don't think that the "Interface" has anything to do with the internal card.

Opps. Yes, you are quite correct Ben. Sorry I misread the post.

OK, just had time to read everything, I'll get a card reader and see whats on the card, I have nothing that can read one.

Andrew, the NAVILINK II function didn't copy any SBN files from the SD card to the dated folder at all, but as you say it is probably on the card. The file types it transfers and saves is the same file types that the memory card convertor should produce from the SBN file, so looks like it is converting them automatically when the card is read.

No Brisbane does'nt have daylight saving, , our cows dont like it, so its + 10 hrs AEST.

Thanks for all your other tips, I'll try all these out

Mr Sailquik, your wisdom has proved invaluable, results speaks volumes. I bought a $10 SD card reader from Strathfield and here are the results from my GPS track from the weekend from Realspeed, excuse the shattering speeds

** SBN file on SD card read from card
2s pk 21.878
5 x 10s av 19.614
Alpha 14.255
NM 14.448
Dist 6.13

** SBP file from the unit downloaded by NavilinkII
2s pk 21.868
5 x 10s av 19.614
Alpha 14.261
NM 14.423
Dist 6.14

** SBP file saved from data logger to SD card and read from card
2s pk 21.878
5 x 10s av 19.614
Alpha 14.261
NM 14.423
Dist 6.14

** Downloaded/converted to NMEA file with NavilinkII
2s pk 21.6
5 x 10s av 19.408
Alpha 14.266
NM 14.048
Dist 6.18

The SBN and SBP files are very similar but the downloaded/converted NMEA file is quite a bit different. I am really surprised by the different results but as you say prob due to rounding off during format conversion. So reading off he card is the way to go, thanx mate

Yeah, we breed our cows down here specially to cope with daylight saving. Unfortunately, our farmers are not quite as adaptable!

There you have it. Direct card copy and use of the .sbn and .sbp files is simple and gives the most accurate results. I am actually a bit puzzled that you still got slightly different results in the Alpha, NM and distance. In theory they should be absolutely identical. Hmmm.... might have a re-run a few of my own files and see what gives.........

The guys from Locosystech are great. They released a new firmware within a week of me telling them about a bug, (does not display max speed over 256km/hr properly), and now they have added a feature that I asked for in a new firmware release, again only a week later.

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Harrow said...

The guys from Locosystech are great. They released a new firmware within a week of me telling them about a bug, (does not display max speed over 256km/hr properly), and now they have added a feature that I asked for in a new firmware release, again only a week later.

Does updating the firmware effect configured settings

No, updating the firmware does not affect any settings. It does not even wipe out the maximum speeds, etc. saved in the speed genie or any of the trip meter data either. (I just updated mine tonight, and checked it all before and after to make sure).

BTW, the new feature that they added for me is "MIN TRIP SPEED", found in "MISC" menu. Put a low speed in this, say 5 knts, and when the speed is less than the figure you set, the trip clock stops counting, and then starts again when your speed goes above the "min speed". This means you will know how long you spent actually on the water, and the "average speed" in the trip meter will not be affected by any resting time you had on the beach. (or time you spend water starting or uphauling ).

Well done Harrow, keep adding those new features, the only thing they missed was giving you credit in the readme file - dam !!

Actually thats a really good feature that you added, I was wondering if it worked that way, and now it does

That's certainly very impressive. Can't think of any other company who'd respond that fast to an upgrade request. Seems like the Loco guys are getting very windsurfing focussed.