Re: geostationary satellite data

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From	Peter Pearson <pkpearson@nowhere.invalid>
Newsgroups	comp.lang.python
Subject	Re: geostationary satellite data
Date	16 Dec 2015 17:53:18 GMT
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On Thu, 17 Dec 2015 04:37:26 +1100, Chris Angelico <rosuav@gmail.com> wrote:
> On Thu, Dec 17, 2015 at 4:30 AM, Peter Pearson
><pkpearson@nowhere.invalid> wrote:
>> 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
>
> Hmm. With just a few exceptions. Maybe it's two channels or something
> - is that what you mean by "taken at different wavelengths"?

Yes; but as described below, I now think they're taken at different times.

> Definitely it's begging for format identification from the source.

Agreed, again.  But it's hard to set this kind of problem aside.

I split it into two images, thusly:

>>> half = len(rawdata)/2
>>> Image.fromstring("L", (9896, 3298), rawdata[0:half]).save("temp3.png")
>>> Image.fromstring("L", (9896, 3298), rawdata[half:]).save("temp4.png")

Flipping between the resulting two images, one sees slight displacements
of the large-scale swirly structures, so I'm pretty sure the two images
correspond to slightly different times.  (I use the current GOES West
northern-hemisphere image as my desktop, so I'm pretty familiar with the
movements of atmospheric swirly thingies.)

This feels solved-enough to set aside now.

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

Thread

geostationary satellite data jorge.conrado@cptec.inpe.br - 2015-12-16 13:19 -0200
  Re: geostationary satellite data Peter Pearson <pkpearson@nowhere.invalid> - 2015-12-16 17:04 +0000
    Re: geostationary satellite data Chris Angelico <rosuav@gmail.com> - 2015-12-17 04:08 +1100
      Re: geostationary satellite data Peter Pearson <pkpearson@nowhere.invalid> - 2015-12-16 17:30 +0000
        Re: geostationary satellite data Chris Angelico <rosuav@gmail.com> - 2015-12-17 04:37 +1100
          Re: geostationary satellite data Peter Pearson <pkpearson@nowhere.invalid> - 2015-12-16 17:53 +0000
        Re: geostationary satellite data Robin Koch <robin.koch@t-online.de> - 2015-12-16 19:57 +0100

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