Garmin Nav Data specs

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Garmin Nav Data specs

Postby dgger » Wed May 18, 2016 7:42 am

I was wondering, if anyone has successfully parsed the nav data as supplied by Garmin/Jeppesen. Specifically, the avtn_db.bin file that is being "programmend" through JDM, etc.

I understand this is not a specific Diamond issues, but I would love to understand this format a little further and given the knowledge gathered in this forum I am hoping someone could push me in the right direction such as official specs, open source flight simulators, etc. that would help me here.

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Re: Garmin Nav Data specs

Postby CFIDave » Wed May 18, 2016 2:06 pm

Haven't parsed the NavData file structure, but if you rename it to "worldwide.bin," you can substitute it for the existing file of the same name in Garmin's $25 G1000 PC Simulator for the DA40 or DA42. Then you can fly all the most current approaches. I'm not sure if this works for the most current version, but it used to work great with the DA40 sim a few years ago
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Re: Garmin Nav Data specs

Postby Rick » Wed May 18, 2016 4:21 pm

CFIDave wrote:Haven't parsed the NavData file structure, but if you rename it to "worldwide.bin," you can substitute it for the existing file of the same name in Garmin's $25 G1000 PC Simulator for the DA40 or DA42. Then you can fly all the most current approaches. I'm not sure if this works for the most current version, but it used to work great with the DA40 sim a few years ago
With the latest version of the PC Sim (v12.00), you simply put your latest avtn_db.bin file in the winfs_mount subfolder under the sim root folder. I've been doing this successfully for several years now, although I seem to remember someone here on the DAN reporting a problem getting this to work... :scratch:
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Re: Garmin Nav Data specs

Postby DavidS » Wed May 18, 2016 11:08 pm

The file format is not documented anywhere AFAIK. It have seen it reverse engineered.

Depending on what you're looking for, the tools used to build Avare maps are freely available and can get you all of the data you're looking for.

Or you can go straight to the FAA and parse their distributed files. That's what I did.

Let me know what you're interested in / trying to accomplish and I might be able to point you the right way.
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Re: Garmin Nav Data specs

Postby dgger » Thu May 19, 2016 1:00 am

Thanks for pointing out Avare. I had completely missed this project and sure will have a good look.

Ultimately, I was hoping to put together an app to update the nav data from within the cockpit - ideally using a mobile device. So, I am much more interested in creating the file rather than parsing it. I fly in Europe and will need to get my data from Eurocontrol (let's see how that goes, but that is another story...).
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Re: Garmin Nav Data specs

Postby DavidS » Thu May 19, 2016 5:15 am

I'd encourage you /not/ to even attempt what you're suggesting as it's a safety of flight issue and very tricky to get right. It's also far more involved than your initial post suggests.

If I were you, I'd just get yourself a spare pair of 4GB Sandisk SD cards (not class 10, class 4 I believe) and write updates at home and swap entire sets of cards when you get to the airport. I find the stand-alone Garmin updaters to be the easiest to deal with. (They appear to cover Europe now.)

Swap officially written cards and keep safety first. :)
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Re: Garmin Nav Data specs

Postby dgger » Thu May 19, 2016 6:52 am

I hear you. Clearly, this is for VFR and information, only. Once, I have a prove of concept, I might go through validation/certification. You never know...

Yes, any SD card of the non-SDHC variety should work.

Are you aware of the Wombat? It is Bad Elf vaporware and might just do exactly that - if it ever materializes.
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Re: Garmin Nav Data specs

Postby CFIDave » Thu May 19, 2016 12:41 pm

dgger wrote:Yes, any SD card of the non-SDHC variety should work.

I used to think the same thing, but it's not true. SDHC cards do work, which is fortunate since it's getting increasingly difficult to buy non-SDHC cards.

Last month I needed to ferry an un-airworthy DA40 XLS (under an FAA ferry permit) to a maintenance facility. This plane was bought from a bank (repossessed by US marshals), where the original owner who had defaulted on his loan had removed all of the original SD cards from the G1000.

I went to a Best Buy store and bought three 8GB SanDisk SDHC cards for about $7 each, bought a PilotPak on the Garmin website using the G1000 System ID for that DA40, and downloaded all the database files to the blank new SD Cards without any reformatting. I used one card to load NavData into the top slots, put the other two cards into the PFD and MFD bottom slots, and everything worked perfectly. :thumbsup:
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Re: Garmin Nav Data specs

Postby Rick » Thu May 19, 2016 1:35 pm

dgger wrote:Thanks for pointing out Avare. I had completely missed this project and sure will have a good look.
I have been using Avare for several years, and it's AWESOME! I still can't believe that the app and the monthly database updates (charts, IAP's, everything) are ALL FREE! If you find it useful, please donate to the developers to keep the new features coming! (This is just my opinion, I have no relationship with the developer in any way...)
dgger wrote:Ultimately, I was hoping to put together an app to update the nav data from within the cockpit - ideally using a mobile device. So, I am much more interested in creating the file rather than parsing it. I fly in Europe and will need to get my data from Eurocontrol (let's see how that goes, but that is another story...).
Legal and safety issues aside, I think you will find it very difficult to accomplish your goal. Garmin has the G1000 locked up from an update perspective. You will notice when you download your monthly DB update from Jepp, you actually get 2 files. The avtn_db.bin file contains the new nav data and IAPs, but there is a second file called feat_unlk.dat that is created by the uploader just for your G1000. This file contains your G1000 system ID (unique to your aircraft) as well as the checksum and version information for the current Nav database file. You can't just simply copy the avtn_db file to your G1000, you must "install" it from the upper slot. During this 'install' process the G1000 verifies the feat_unlk information before accepting the new Nav DB data into its fold. This is what keeps someone from buying a Nav subscription and then sharing it with their friends, or a flight school from updating all of their G1000's off a single subscription, etc. I suspect this will also make it very difficult for you to make any updates to the Nav data on your own, even if you could create an acceptable avtn_db.bin file.
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Re: Garmin Nav Data specs

Postby DavidS » Thu May 19, 2016 1:43 pm

re: SDHC, it may be device dependent.

re: Wombat, that's clever. It's probably safe to assume they're working with Garmin under NDA because what they're doing would require the ability to generate valid image checksums for the DRM the G1000 uses. You may find experimenting and playing around with the "area" handhelds rewarding.

re Avare, well, it's ugly as all hell. :)
All of the information they use is published by the FAA. The crowd-sourced geo-referenced plates was a neat period. (They asked all their users to manually tag the references on the plates...)

The Foreflight guys once told me at <some aviation event> that they have trouble with the FAA data because of inconsistencies. That seemed like a bizarre statement to me, almost as if they were trying to justify their value add /that/ way. (We were talking about vector charts, like what Garmin Pilot has.)

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