Dive logging with the Mk1

I am interested to here from those people that have been lucky enough to be beta testers of the Mk1 with regards the level of detail in the log it produces for each dive. I like a lot of detail about depth and temperature for my dives as I sync this with my photographs so I know the depth and temperature for each photograph - I do quite a bit of citizen (and real) science with the data.

I assume it creates (or you can export) an XML file much like the other Garmin devices. How often does it log depth? (e.g. every 5 seconds) How often does it log temperature? What is the precision of the depth and temperature data? (i.e. how many decimal points?)

How accurate do you think the temperature data is? I have a Citizen Hyper Aqualand which is very accurate with regards temperature (I've tested it against scientific thermometers). My Oceanic Atom 3.0 is so inaccurate with temperature (usually 2 C cooler than the real temperature but can be 1 or 3 C out). My Shearwater Perdix AI is eventually quite accurate but a) being so large it holds heat and so doesn't display accurate temperature until 10-20 minutes into a dive, and b) only logs to the nearest degree.

Thanks.

0 rjanuary over 7 years ago

I don't have exact answers for everything you've asked at the moment, but did at least want to let you know what I can pull from the top of my head. The default sample interval appears to be 1 second. That is for depth and temperature data.
The logs are exposed as a set of "fit" files via USB mass storage.

Garmin makes the SDK available for free download. The base file format is documented and easily consumable. Most of my analysis is done in python, where I found python-fitparse very handy. It does not correctly identify all data fields by name at the moment, however it is all exposed via field number. In my free time I've been working to identify those fields and update the library. Unfortunately I haven't had the opportunity to clean that work up to submit a pull request.

I also can't directly answer the absolute temperature accuracy. That's something I may try to test over the next week. I can tell you that all test units I've dove with have agreed with one another, verified within 1* F to my primary computer in a static environment, and temperature repeatability has been consistent.
Since the mass of the device is much smaller than other computers, it does also update much more quickly than other computers I've dove. I've heard the Perdix is slow to update, as is my primary Scubapro G2.

0 atj777 over 7 years ago

I don't have exact answers for everything you've asked at the moment, but did at least want to let you know what I can pull from the top of my head.

Thanks! I appreciate it.

I remember my old Forerunner 310XT created both FIT and TCX files. I wonder if you can export a TCX file from Garmin Connect web page with all the data in XML format.

A sample interval of 1 second sounds more than adequate for my purposes. My Citizen does 5 seconds for depth and 5 minutes for temperature so this should be better.

This device certainly sounds very promising and could replace my Citizen Hyper Aqualand, my vivoactive and my etrex 10 all in one device. oh... and my Mio FUSE, too (for HR). It is just a pity it isn't air integrated (yet).