Thread: Garmin Birdseye JNX format hacking

I've found additional info on JNX format here

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unfortunately this page is in Russian only.

looks like some on in russia is carrying out the sam research....

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I have translated the research from russian using google translate.

JNX

Briefly about the format
Files in JNX used in Garmin maps to display maps service BirdsEye.
The main pluses JNX compared with maps Custom Maps (KMZ):
(Seemingly) unlimited number of fragments of maps;
multiple levels of detail;
high speed display device map.
A significant drawback is its size JNX rigid adherence to the device.


The purpose of picking
Since BirdsEye services from satellite imagery in Russia can not tolerate any criticism, really want to somehow accommodate the tile format for displaying JNX genshtabovskih and other scanned maps on the new devices Garmin, not to be tied for the loss of the format KMZ.
If it is possible to fully understand how to make your own JNX and make arbitrary garminovsky navigator (with support JNX, of course) to work with these JNX, it will be possible to make converter card format OziExplorer format JNX.


Internal Structure
The information below is still very imprecise and are the result of a preliminary study. It is likely that dropped from consideration any important files region JNX.
File format JNX can be divided into 5 parts:
title;
table with a description of levels;
Service information loader maps;
table describing the tiles;
a set of tiles.
Now a closer look at each of these parts.
Note 1: All two-and four-byte fields below, using "Intel's" byte order, ie the least significant byte first, and then the older ones.
Note 2: In all tables below, except for the description of the title, the bias will be relative to the beginning of the file, unless otherwise stated.


1. Title
Offset from the beginning
Header Field Type Description
0x00 int32 Apparently, the signature. In all JNXah in this field is kept value 0x00000003.
0x04 int32 ID device for which makes the card. In the demonstration maps, this field is zero.
0x08 4 int32 coordinates, which draws a card. Description of the system of coordinates, see below.
0x18 int32 Number of levels of detail.
0x1S 5 int32 Apparently, there is stored binding code to the device. The format of the fields is not yet known.

On the coordinates used in the files JNX.
Coordinates are stored as a landmark 4-byte integers. Two pairs of numbers describe the coordinates of two corners of cards (the importance of the sequence of angles is not yet clear). The first value in the pair is the latitude, the second - longitude.
To obtain the coordinates of these integers must be divided by 0x7fffffff, and then multiply by 180.
Example. Assume the file contains the coordinates of 0x1FCD7932, 0x1ADEBDDA. After conversion, the coordinates of N 44 ° 43'20 .81 ", E 37 ° 47'9 .80".


2. Table describing the levels
Number of levels of detail in the header specifies the number of elements in this table.
Structure elements: the Offset from the beginning
Table Field Type Description
0x00 int32 Number of tile per level.
0x04 int32 offset to the description of the first tile at the level.
0x08 int32 Apparently, the scale at which shows the level of the tiles.

As used and that the mean value in the field scale, it is not clear.
In the JNX, I have seen the value of the field scale were as follows: 0x12A95 (76,437) at the first level, 0x12A9 (4777) on the second, 0x4AA (1194) or 0x255 (597) in third.


3. Service information loader card
This file is part of the JNX, apparently, is not used for displaying maps. Then keeps a list of URLs from which it downloads the individual tiles, as well as specified GUID maps and copyrights.

4. Table describing tile
Offset from the beginning
Table Field Type Description
0x00 4 int32 Coordinates single tile.
0x10 int16 width of the image.
0x12 int16 height of the image.
0x14 int32 image size in bytes.
0x18 int32 offset to the image.



5. A set of tiles
Tiles are the usual images in JPG, of which vykusheny markers SOI (ie, the initial two bytes of 0xFF, 0xD8).
Most of the images have a resolution of 256 by 256 pixels.



Until all.
If you have any comments or additions to the format JNX, please write to the author.
Also, I would highly appreciate if send are small (less than 5 megabytes) do not examples of demonstration files JNX.

Project is comming along nicely.

Please show your support more details can be found here.

Sorry for post other people forums in this post.

If people would like to help please search for JNX file format hacking and look for another GPS underground website.

If you would like to read the current finding the owner of the orignal JNX file format site has kindly convert it to english so please check it out here.

Code:

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