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  1. #1
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    Default Creating my own JNX map for Etrex 20

    Thanks for your links. I have already made a start. My project involves converting a few of the Nepal Topo maps downloaded from here:
    Code:
    Please Login or Register to see the links
    and converting them to *.jnx to load into an Etrex 20.

    I have applied the jnx patch to the Etrex successfully. My first problem was finding a GUPDATE.GCD file to patch since none was present in my device. Apparently it is deleted when the last update installs and since the firmware was already up to date I could not download another update from Garmin. Managed to find an alternative here:
    Code:
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    I downloaded eTrex20_30_Webupdater__430.gcd and extracted into the Device:\Garmin folder. Do not restart the device. The update file must not be used until it is patched. Remove any existing *.jnx files from the Birdseye folder. eTrex20_30_Webupdater__430.gcd was renamed to GUPDATE.GCD, Then it was just a question of using the jnxpatcher and instructions here: [Only registered and activated users can see links. ].

    Needed to use the option to reset the update no to 431.
    Used the trial jnx file in the thread to confirm it was working.

    Creating my own JNX files is being done using MAPC2MAPC:
    Code:
    Please Login or Register to see the links
    Registered copy gets rid of all the red crosses - happy to part with 15 for the privelege.

    Some problems calibrating the maps initially, using Lat/Long and WGS 84 projection . They were appearing about 250m out of position when compared with Google Earth.
    Now have a sample successfuly calibrated using the Google Earth method here:
    Code:
    Please Login or Register to see the links
    Last thing was to adjust the JNX scale to control the zoom level at which the map appears, using JNXSCALE from here:
    Code:
    Please Login or Register to see the links
    Scale was set to 2388 which makes them appear at about the correct resolution on the device. Seems a bit random though.

    I have around 10 maps I intend to convert. They appear as individual jnx files in the device and can be separately turned on and off but I might merge them when they are all done if I can figure that out. Also may be useful to have different levels of detail and different zoom levels but I dont think MAPC2MAPC does that so maybe a different utility would be needed. More to learn.

    Sorry if this lengthy post is in the wrong place.



    Please code all external links as per [Only registered and activated users can see links. ] to avoid refback!
    Last edited by Neil; 6th February 2016 at 22:06.

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  3. #2
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    Hi Ashe,

    I have moved your post from [Only registered and activated users can see links. ] to a more appropriate place.
    Please note all external links (except download links to file hosting sites) must be coded to avoid refback. Thanks.
    To avoid clutter, please don't leave any "Thank You" posts but use the Xlosbkb button or the LIKE this post ↑ link instead
    (found at the lower left hand side of any post)
    To see hidden download links, use the same LIKE this post ↑ link and hit F5 on the keyboard to refresh the page.
    Report broken download links by using the ADYp6au button at the lower left hand corner of that post.

  4. #3
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    Thanks for moving this to a more appropriate location.
    If its of interest I will continue to add to this thread as I progress.
    I realise that I'm doing nothing new, just pulling together methods and information from various existing sources.

    Ashe

  5. #4
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    Although you're not doing anything new, sharing your method and approach may certainly be of interest to some of our members who are getting their feelers out to do the same.

    Please do share!
    To avoid clutter, please don't leave any "Thank You" posts but use the Xlosbkb button or the LIKE this post ↑ link instead
    (found at the lower left hand side of any post)
    To see hidden download links, use the same LIKE this post ↑ link and hit F5 on the keyboard to refresh the page.
    Report broken download links by using the ADYp6au button at the lower left hand corner of that post.

  6. #5
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    @ Some problems calibrating the maps initially, using Lat/Long and WGS 84 projection .

    You have to use the input data from map notes for calibrating - coordinate format, spheroid and projection only!!! After calibrating you have to save a project as Lat/Long and WGS 84 before converting to JNX.

    @ I have around 10 maps I intend to convert. They appear as individual jnx files in the device and can be separately turned on and off but I might merge them when they are all done if I can figure that out. Also may be useful to have different levels of detail and different zoom levels but I dont think MAPC2MAPC does that

    If your map is not overlapping and have the same scale you may to use the same Product ID and Product name. Cropping of borders is required! In this case all map will be under the one checkbox in list of map. If you use maps with a different scale I recommend to use Product ID and Product name separately for each scales. It is better than the one multilevel JNX because you can play with appearance of map on screen through device menu.
    Love your wife? Buy yourself a GPS for answering to her favorite question: "Dear, where are you?".

  7. #6
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    Thanks for the comments Giomen. I think I have solved my calibration problem.

    In MAPC2MAPC my work flow is as follows (using the Wizard interface):
    Load an Image File and Calibrate it
    Calibrate with Map Coordinates
    Then my error. I was using Latititude Longitude /WGS84 for calibration. --- and using the Lat/Long figures printed on the map corners.

    I have changed this to Other Grid and Selected Nepal ---- duh! obvious I guess.

    So instead of working with the Lat/Long of the corners I am working with the map grid coordinates.
    Results viewed in Google Earth align well with the Google Earth image detail.

    Test map Kathmandu.kmz is here
    Code:
    Please Login or Register to see the links
    Next I have to crop the borders from my map set in Photoshop.
    Problem -- the map border is not quite square to the map grid. The border is aligned on the Lat/Long lines.
    So I think I will have to warp the map in Photoshop to make the borders rectilinear, so then I can crop the image with the Photoshop crop tool and hopefully the calibration will still work.

    When it comes to setting the JNX scale I have read elsewhere on this site:
    JNX format description contains the following "standard" set of scale values, which is recommended to use in the hand-made JNX maps: 75, 149, 298, 597, 1194, 2388, 4777, 9554, 19109, 38218, 76437, 152877, 305758, 611526, 1223072, 2446184.

    This set is an extension of the set used in BirdsEye subscription maps: 597, 1194, 4777 and 76437.
    Still, there were no explanation of what these numbers mean.
    Is there any clue to how these relate to display scale distances as seen on the Etrex screen?
    I have found that using a JNXScale of 2388 makes the map appear when the 800m scale is visible on the Etrex and when the 1km scale is visible in Basecamp.
    Last edited by Hampden; 7th February 2016 at 15:49.

  8. #7
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    Moving on from trials, all seems to be working well now.
    All visual testing in Google Earth.
    Discovered that Photoshop CS6 has a Perspective Crop Tool which does exactly what I needed. Crops and straightens in one go.

    Done two map areas this afternoon. Looking good enough for my needs. Joint between the maps is visible but good enough.
    This is the kmz in Google Earth. Retaining long file names since it seems to make no difference in GE or Etrex 20

    Image01 zpsnnlkokig
    Last edited by Hampden; 7th February 2016 at 17:32.

  9. #8
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    Below there is my table for zooms and scales:
    "Zoom level (m, km)" - no comment it is zoom from device screen.
    "Lower visible JNX scale value" - it is general issue
    "Alex" - it is recommendation of author (if empty so this is intermediate and neutral zoom on device which is not depended of scale of JNX and it is the same as corresponding high level)

    Spoiler: My table
    "Zoom level (m, km)" "Lower visible JNX scale value" "Alex"
    5m 14
    8m 21
    12m 32
    20m 52 75
    30m 79
    50m 131 149
    80m 209 298
    120m 313
    200m 521 597
    300m 782 1194
    500m 1303
    800m 2084 2388
    1.2km 3125 4777
    2km 5209
    3km 7813 9554
    5km 13021 19109
    8km 20834
    12km 31250 38218
    20km 52084 76437
    30km 78125
    50km 130209 152877
    80km 208334 305758
    120km 312500
    200km 520834 611526
    300km 781250 1223072
    500km 1302084
    800km 2083334 2446184
    1200km - 4891969


    P.S. I think you can to determine borders of the actual image in MAPC2MAPC with input data for project - it will be equal cropping in export in JNX.
    Love your wife? Buy yourself a GPS for answering to her favorite question: "Dear, where are you?".

  10. #9
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    Thanks for that very useful Zoom table.

    My first attempts to crop the map borders were done using the MAPC2MAPC tool, however this seems to require that the map image is a perfect rectangle.
    The MAPC2MAPC tool uses only two points to define the crop boundary.
    I have not found any way within MAPC2MAPC to crop an irregular trapezoidal shape.

    In my Google Earth trial I have some joints where a "gap" of up to 3 pixels appears when viewed in GE.
    Maybe my border cropping is not accurate?
    My four reference points for calibrating the map are at the first grid intersection inside the map on each corner -- not the corners, since these are not at grid intersections (corners actually at Lat/Long intersections).

    Multiple jnx files load ok in Etrex 20. I have a nice block of 6 maps (3x2) loaded up, covering the eastern half of the Annapurna region.
    Last edited by Hampden; 8th February 2016 at 12:30.

  11. #10
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    @ that the map image is a perfect rectangle.

    Usually all map is a perfect rectangle if use the right projection.

    @ In my Google Earth trial I have some joints where a "gap" of up to 3 pixels appears when viewed in GE.
    Maybe my border cropping is not accurate?

    It is normally for quick work. No doubt it give the error but on this scale this error is a negligible for practice. Errors in GPS position and map are more significant. You can play with calibration again and again to see the perfect merging but it be waste time. Try to get some tracks from open source and put it on your map - it is more reliable for map verification.
    Love your wife? Buy yourself a GPS for answering to her favorite question: "Dear, where are you?".

 

 
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