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praetorian1980, posted Thu Apr 23, 2020 1:21 pm (56224)

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I would like to ask for help extracting and reimporting map files. I know that the map format inside the encrypted file is in (jp2) as can be seen from the header or metadata inside the file but other than that I have no idea where to start.

Thanks

aluigi, posted Thu Apr 23, 2020 5:25 pm (56231)

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Better to upload the original file.

praetorian1980, posted Thu Apr 23, 2020 7:04 pm (56238)

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Attached.

aluigi, posted Fri Apr 24, 2020 9:34 am (56250)

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Just for dumping the jp2:

Code:

findloc OFFSET binary "jP  "
math OFFSET - 8
goto OFFSET
get SIZE long
savepos OFFSET
get NAME basename
string NAME   ".jp2"
log NAME OFFSET SIZE

I don't know if other hgt files have more files inside, if you have a bigger hgt I can check it.

praetorian1980, posted Fri Apr 24, 2020 10:28 am (56253)

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Attached

https://gofile.io/?c=QXI5BC

aluigi, posted Sat Apr 25, 2020 11:32 am (56270)

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Same format so it's ok to use the script.

praetorian1980, posted Sat Apr 25, 2020 12:18 pm (56273)

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aluigi wrote:

Same format so it's ok to use the script.

Do you mean this code that you posted earlier?

Quote:

findloc OFFSET binary "jP "
math OFFSET - 8
goto OFFSET
get SIZE long
savepos OFFSET
get NAME basename
string NAME ".jp2"
log NAME OFFSET SIZE

Is it possible to reimport back into the hgt?

praetorian1980, posted Sun Apr 26, 2020 5:59 am (56287)

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In the zip there is also a ter file. Are you able to extract its contents?

aluigi, posted Sun Apr 26, 2020 8:38 am (56290)

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I don't know what type of file is that.
It starts with "version" and I guess it's related to "terrain"

praetorian1980, posted Sun Apr 26, 2020 4:41 pm (56300)

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I think that the hgt are imported using a codec called jasper, but I don't know how to build it from github.

praetorian1980, posted Tue Apr 28, 2020 3:48 pm (56345)

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I have one question:

I tried comparing a file generated from xnconvert which uses jasper jp2 codecs, with the that hgt file, but I can't decypher what's written in the header. I think, from what I saw, that the hgt file is just a regular jp2 image exported from a jasper codec app in a particular export setting and has a header added to it with information that appears to be, among other things, georeference for the map. If only I could understand what's written in there, I could manually edit the header of new images exported with this codec. Please help.

aluigi, posted Wed Apr 29, 2020 5:54 pm (56383)

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There are various 32bit fields in the header and I'm not sure what they mean.