Nikon BarometerInfo

Added by Juergen Rose 8 months ago

I would like to read the BarometerInfo (Altitude) with exiv2. It is possible to get this information with exiftool (Nikon.pm).
An example file is attached.


Replies (4)

RE: Is there a possibility to get the BarometerInfo of Nikon 1 cameras with exiv2? - Added by Robin Mills 8 months ago

It's in Exif.GPSInfo.Altitude

644 rmills@rmillsmm:~/gnu/exiv2/trunk $ exiv2 -pa --grep bar/i --grep alt/i http://dev.exiv2.org/attachments/download/1060/25850685556_622312410d_o.jpg
Exif.GPSInfo.GPSAltitudeRef                  Byte        1  Above sea level
Exif.GPSInfo.GPSAltitude                     Rational    1  1601 m
Xmp.exif.GPSAltitude                         XmpText     6  1601/1
Xmp.exif.GPSAltitudeRef                      XmpText     1  Above sea level
645 rmills@rmillsmm:~/gnu/exiv2/trunk $ 

RE: Is there a possibility to get the BarometerInfo of Nikon 1 cameras with exiv2? - Added by Juergen Rose 8 months ago

Thanks Robin for your answer. Exif.GPSInfo.GPSAltitude is not the barometric altitude information, but the GPS information. exiftools shows to Altitude values:

rose@lynx:/home/rose/Txt/projects/Robina(163)$ exiftool Testphotos_Exif/Nikon_1/25850685556_622312410d_o.jpg | grep Altitude
Altitude : 1583 m
GPS Altitude Ref : Above Sea Level
GPS Altitude : 1601 m Above Sea Level

i.e., the difference is about 20 m. This difference could be relevant for us. In /usr/lib64/perl5/vendor_perl/5.24.0/Image/ExifTool/Nikon.pm
I find:

rose@lynx:/home/rose/Txt/projects/Robina(169)$ grep -U2 "MakerNote\|BarometerInfo\|Altitude" /usr/lib64/perl5/vendor_perl/5.24.0/Image/ExifTool/Nikon.pm
  1. 13) Roger Larsson private communication (tests with D200)
  2. 14) http://homepage3.nifty.com/kamisaka/makernote/makernote_nikon.htm (2007/09/15)
  3. 15) http://tomtia.plala.jp/DigitalCamera/MakerNote/index.asp
  4. 16) Jeffrey Friedl private communication (D200 with firmware update)
  5. 17) http://www.wohlberg.net/public/software/photo/nstiffexif/
    --
    CHECK_PROC => \&Image::ExifTool::Exif::CheckExif,
    WRITABLE => 1,
    GROUPS => { 0 => 'MakerNotes', 2 => 'Camera' },
    PRINT_CONV => \&FormatString,
    0x0001 => { #2 # the format differs for different models. for D70, this is a string '0210', # but for the E775 it is binary: "\x00\x01\x00\x00"
    Name => 'MakerNoteVersion',
    Writable => 'undef',
    Count => 4,
    --
    },
    0x00c3 => {
    Name => 'BarometerInfo',
    SubDirectory => {
    TagTable => 'Image::ExifTool::Nikon::BarometerInfo',
    ByteOrder => 'LittleEndian',
    },
    --
    Flags => [ 'Binary', 'Protected', 'Drop' ],
    Notes => q{
    this data is dropped when copying Nikon MakerNotes since it may be too large
    to fit in the EXIF segment of a JPEG image, but it may be copied as a block
    into existing Nikon MakerNotes later if desired
    },
    SubDirectory => {
    --
    WRITE_GROUP => 'NikonScan',
    WRITABLE => 1,
    GROUPS => { 0 => 'MakerNotes', 1 => 'NikonScan', 2 => 'Image' },
    ...
    %Image::ExifTool::Nikon::FileInfo = (
    %binaryDataAttrs,
    GROUPS => { 0 => 'MakerNotes', 2 => 'Image' },
    FORMAT => 'int16u',
    0 => {
    --
  1. ref PH
    %Image::ExifTool::Nikon::BarometerInfo = (
    %binaryDataAttrs,
    GROUPS => { 0 => 'MakerNotes', 2 => 'Location' },
    0 => {
    Name => 'BarometerInfoVersion',
    Format => 'undef4',
    Writable => 0,
    },
    6 => {
    Name => 'Altitude',
    Format => 'int32s',
    PrintConv => '"$val m"', # (always stored as metres)
    ...

If I interpret this correctly, the BarometerInfo starts with an offset of 0x00c3 in MakerNotes. But I have no idea, how can access this information with libexiv2.

RE: Is there a possibility to get the BarometerInfo of Nikon 1 cameras with exiv2? - Added by Robin Mills 8 months ago

Please raise an issue and this will be investigated for a future release.

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