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Garmin jnx file format hacking

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  • Re: Garmin jnx file format hacking

    I argee trimming would be the best option

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    • Re: Garmin jnx file format hacking

      Please let me introduce "sparse" JNX maps.

      After WHITEDRAG0N asked about the map splitting, I've made an interesting experiment - I've downloaded 6x6 tiles square area in Mobile Atlas Creator, and split the tiles into two folders, like this:

      Tiles in folder 1:
      Code:
      * * * * * *
      * * * * * *
      * * *
      Tiles in folder 2:
      Code:
            * * *
      * * * * * *
      * * * * * *
      * * * * * *
      Just like we've encountered the limit in one of the rows, and switched to the next JNX file with the rest of the tiles.
      After this I've made JNX files from these two folders, and GPS unit could successfully join these JNX, forming a normal square map.

      I'm attaching an archive with two sample JNX files. First of them has three levels - the first two levels are square low-quality, while the third has a non-convex layout.
      And the second file only has one level, which complements the 3rd level of the first JNX.
      sparse_jnx.zip
      To see the map, scroll to about N52°50', E99°00'.

      To summarize: it's possible to split JNX files, when the tile limit is reached.
      Garmin GPSMAP 62s

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      • Re: Garmin jnx file format hacking

        Here's another iteration of MOBAT2JNX. This one trims the upper layers so that they match the lowest layer. There is an optional second MAXTILES parameter which applies to the lowest layer. If there are more than this number the map is cut equally into separate JNX files with the cut pieces running west to east. Default value for MAXTILES is 48000. So if you have 60000 tiles, you end up with two maps of about 30000 tiles (depending how the cuts fall).

        No changes to scaling, yet.

        ... and the latest version of MAPC2MAPC now supports writing JNX - but you have to reproject (Edit>Warp Map) if the map is not already aligned.
        Attached Files
        Last edited by roger47; 4th January 2011, 19:56.

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        • Re: Garmin jnx file format hacking

          Originally posted by roger47 View Post
          ... and the latest version of MAPC2MAPC now supports writing JNX - but you have to reproject (Edit>Warp Map) if the map is not already aligned.
          It's quite possible, that JNX can support the tiles up to 1024 x 1024 pixels. Could you please make a test version of MAPC2MAPC with adjustable tile size for JNX files (this can be the same tile settings already present in the Preferences dialog box)?

          I've tried to make two JNX files with JPEG Quality set to 5, and to 1, and the fiies I got have the same size. Doesn't MAPC2MAPC use the JPEG Quality setting when writing JNX?
          For a matter of testing, it would also be great, if Advanced Garmin Tile Control option would also affect the JNX maps creation.
          Last edited by Whiter; 5th January 2011, 02:37. Reason: misspelling fixed
          Garmin GPSMAP 62s

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          • Re: Garmin jnx file format hacking

            Tiles up to 1024 x 1024 works ok

            Good point !!

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            • Re: Garmin jnx file format hacking

              Originally posted by dodoche View Post
              Tiles up to 1024 x 1024 works ok
              Have you tried any larger tile sizes? Say, 2048 x 2048?
              How fast does the 1024-pixels JNX work compared to the 256-pixels one at the same coordinates?
              Garmin GPSMAP 62s

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              • Re: Garmin jnx file format hacking

                Here's a special version of MAPC2MAPC to try. This is just an EXE so put it in the same folder in Program Files. It takes tile size and quality from Preferences.
                Attached Files

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                • Re: Garmin jnx file format hacking

                  Sorry I haven't tried different options... i won't have time today to try, if someone can try different settings..

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                  • Re: Garmin jnx file format hacking

                    Thank you!

                    I tried to make a JNX with tile size 2048 x 2048, my GPS unit loaded the map, but didn't show it.
                    So 1024 x 1024 - is the max. supported tile size.
                    Last edited by Whiter; 5th January 2011, 07:51. Reason: other tile sizes
                    Garmin GPSMAP 62s

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                    • Re: Garmin jnx file format hacking

                      Originally posted by Whiter View Post
                      Thank you!

                      I tried to make a JNX with tile size 2048 x 2048, my GPS unit loaded the map, but didn't show it.
                      So 1024 x 1024 - is the max. supported tile size.
                      I tried to make a JNX with tile size 2048 x 2048, my oregon550 v432 beta loaded the map and show it

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                      • Re: Garmin jnx file format hacking

                        Originally posted by ana550 View Post
                        I tried to make a JNX with tile size 2048 x 2048, my oregon550 v432 beta loaded the map and show it
                        Oops. I re-tested that. My 62s shows that map too. But it takes about 5-6 seconds before the tiles become visible for the first time. In my previous test, I've turned the unit too soon - before the map appeared.

                        Interesting. What is the tile limit then?
                        Garmin GPSMAP 62s

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                        • Re: Garmin jnx file format hacking

                          I've played a bit with the different tile sizes in JNX, and it appears that when the tiles are bigger than 1024 x 1024, the device downsizes them.
                          Please check attached test map: test.zip. Its image only consists of of black lines on white background, and you can easily check what tile sizes in JNX lead to accurately-looking results.

                          Please let me quote TRAILTECH:
                          Images over 1 mega pixel (1024x1024 pixels, 512x2048 pixels, etc.) will be rendered at a reduced resolution on the unit.
                          This was about KMZ, but it seems that it also applies to JNX.
                          Here's what I got:
                          1024 x 1024 - Ok
                          2048 x 2048 - rescaled tiles
                          512 x 2048 - Ok
                          600 x 2048 - rescaled
                          600 x 1747 (0.9996 megapixel) - Ok
                          Garmin GPSMAP 62s

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                          • Re: Garmin jnx file format hacking

                            I was having a think about "sparse" jnx maps and was wonder if the following was true. I might give it a go later today.

                            if i had a large are covered by a map but some area at the edge of the map where unwanted due to water or plany just not required

                            would the GPS display all the tile surrounding the missing tile's

                            will let you all know of my results later.

                            I have now carried out the experiment and confim it does indeed work.

                            I downloaded a 6 by 6 grid and removed the centre tile i then convereted using the latest MOBAT2JNX and uploaded into my oregon 200

                            all tiles where displayed apart from the removed tile also no error where detected.

                            This would suggest to me that we can upload non square maps and remove any unwanted tiles and thus make the JNX more afficent.

                            this would come in handy when doing coast lines
                            Last edited by WHITEDRAG0N; 6th January 2011, 10:14.

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                            • Re: Garmin jnx file format hacking

                              When I've proposed the "sparse" JNX, I though it would be useful to split levels with more than 50000 tiles into several files, forming some kind of multi-volume maps.

                              Good to see that there will be more than one application
                              Garmin GPSMAP 62s

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                              • Re: Garmin jnx file format hacking

                                Roger Would it be possible to scan thought a OSM tile storage map and remove all blank or mono color tiles. Ie remove all white tiles.

                                Dont know if this is possbile would be nice

                                I want to remove all white tile round a coast line.

                                Cheers

                                whitedrag0n

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