Path: csiph.com!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: Peter Pearson Newsgroups: comp.lang.python Subject: Re: geostationary satellite data Date: 16 Dec 2015 17:53:18 GMT Lines: 39 Message-ID: References: X-Trace: individual.net bWIfoihBoRqnB3DU2F4k/QP6rIiqrdmWCycK6722aK++aQ0Ecx Cancel-Lock: sha1:Nyj7e0L4o89tJ9aued/DUGdkWQk= User-Agent: slrn/pre1.0.0-18 (Linux) Xref: csiph.com comp.lang.python:100532 On Thu, 17 Dec 2015 04:37:26 +1100, Chris Angelico wrote: > On Thu, Dec 17, 2015 at 4:30 AM, Peter Pearson > 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.