Garmin jnx file format hacking

[gaga55]

In this case, this is the number of seconds since December 30, 1988, 12:00 PM.
But I cannot recognize this as any standard date/time format

I have
71 58 FE 27 00 00 00 00
in 4 different files. To see whether you got the algorithm right, what do you calculate for the expiry date? (I'll let you know after your guess)

[Whiter]

I have
71 58 FE 27 00 00 00 00
in 4 different files. To see whether you got the algorithm right, what do you calculate for the expiry date? (I'll let you know after your guess)

I've made a mistake in the message above. Not since December 30, 1988, but since December 30, 1989.

If I got it correctly, then your subscription will expire on April 5, 2011. Am I right?

[gaga55]

That's right!
However, while Garmin myMaps (online) gives April 5 2011, Basecamp says April 6 2011.

I hope you make further progress, I'd love to be able to make jnx files from any image file.
Thanks for your effort.

[roger47]

HI Guys,

I'm the developer of MAPC2MAPC. Maybe I can add creation of JNX files to it. But I don't have a Garmin Unit and may need someone who I can send test files to - if I get that far! Any volunteers?

[Whiter]

I'm the developer of MAPC2MAPC. Maybe I can add creation of JNX files to it.

That would be great!

But I don't have a Garmin Unit and may need someone who I can send test files to - if I get that far! Any volunteers?

I'd gladly help you with testing.

[roger47]

If we're creating maps, what is the downside of making them all 'demo' maps - with zero expiration dates, control codes etc? It would make the task easier. And does anyone know the map projection used for the 'tiles' : are they Mercator (like Google Maps and most 'mobile atlas') or Plate Carree like Google Earth

[Bill_clark]

HI Guys,

I'm the developer of MAPC2MAPC. Maybe I can add creation of JNX files to it. But I don't have a Garmin Unit and may need someone who I can send test files to - if I get that far! Any volunteers?

Hi,

I'm volunteer to do any tests! :-)

I have an Oregon 450.

Bill.

[WHITEDRAG0N]

Wooh Project seems to realy taking off now.

Roger i have and oregon unit and i am willing to test files for you. I can only see 1 problem with setting the them all to demos maps.

When basecamp outputs a demo map it limits is viewable area size. This may also be a limitation in the firmware of the unit. I suggest we try a large file with and with out a zero expriation date.

Havent a clue what the projection is.

[Whiter]

If we're creating maps, what is the downside of making them all 'demo' maps - with zero expiration dates, control codes etc?

The device shows only one demo map, and refuses to load all other.

And does anyone know the map projection used for the 'tiles' : are they Mercator (like Google Maps and most 'mobile atlas') or Plate Carree like Google Earth

Is there any easy way to identify this?
I can make a JNX with some specific coordinates, and then check what values are in the file.

[roger47]

I've take the demo.zip that Whitedragon posted on 4th. I've decoded the fields and built the JPGs - seems to be an airfield.

I'll try and build one later as a 'demo' just to prove the principle.