geostationary satellite data

[Peter Pearson]

On Thu, 17 Dec 2015 04:08:02 +1100, Chris Angelico <rosuav at gmail.com> wrote:
> On Thu, Dec 17, 2015 at 4:04 AM, Peter Pearson
><pkpearson at nowhere.invalid> wrote:
>> The file is 65274016 bytes long.  You claim the dimensions are
>> 9896 x 3298, but that comes out to half that number (32637008), so I'll
>> bet the real dimensions are 9896 x 6596, with one byte per pixel.
>> I think this image format is called "raw".
>
> It could be 16 bits per pixel. Without knowing a lot more about the
> source of the image and its format, it's hard to say with any
> certainty.

Agreed.  It's annoying when an agency goes to the trouble of making
huge datasets available online, but fails to identify the format.

But the 16-bits-per-pixel hypothesis is unlikely, given that each
byte tends to echo its predecessor:

0000130 ffff ffff ffff ffff ffff ffff ffff ffff
0000140 ffff ffff ffff c0ff c1c0 c3c3 c3c3 c4c4
0000150 c4c4 c3c4 c3c3 c4c4 c3c3 c3c3 c3c3 c3c3
0000160 c4c4 c4c4 c5c4 c6c5 c7c7 c7c7 c5c5 c6c5

When you decompose this data file as a one-byte-per-pixel, 9896 x 6596
image, the resulting image shows two nearly identical strips, one above
the other.  That suggests interlacing, except that the top strip has
some "bites" missing that aren't missing from the bottom strip.  My best
guess is that it's just two images glued together, maybe taken at
different wavelengths.

-- 
To email me, substitute nowhere->runbox, invalid->com.