Originally Posted by
AlphaZuluRomeo
But when you demand "more" (i.e. precise GMT timing), then by definition you are demanding something that is not raw data.
Indeed I think Dozy'point was that raw data should not be altered ; that means nothing added nor removed.
If not, then they are no raw data anymore, but a transcription.
Got it in one. Also, if HN39 is correct that they had to go to an outside agency to extract the data in a format they could use (apparently hard copy in this case), then they would not have been able to easily rework it into a digital format again. I reiterate - in computing/information science terms the state of the art in 1988 would by today's standards be considered not just incredibly primitive, but also awkward to use, time-consuming and expensive. Particularly of note is that not only did microcomputer paradigms differ from mainframe/minicomputers in general, but even among microcomputers there was no universal standard for representing data - the norm was a mishmash of proprietary formats, all of them incompatible with each other. Transferring data was theoretically possible, but every byte would have to be individually hand-checked to ensure the data was identical at both ends.
It is therefore entirely understandable that the BEA simply tacked a copy of the raw output to the report as an appendix. I'd also be inclined to suggest that because the output is clearly raw data dumped to hard copy, it rather undermines the "tampered data" allegations. Ironically, according to Airbus's response it was the outside investigator's lack of experience with this new data format that caused him to misinterpret the synchronisation.
EDIT (as HN39's post is a useful illustration!) :
Originally Posted by
HazelNuts39
Data acquisition systems output a binary file sequenced in four-second frames.
Each frame is divided into four one-second-subframes.
Each subframe is divided into 64, 128, 256 or 512 “words” of 12 bits each, depending on the FDR’s technology.
The bit is the basic binary unit whose value is either 0 or 1.
A 12 bit word can have values from 0 to 4095.
And if that description sounds complicated enough to begin with, I suspect that in 1988 one would require specialist hardware and software to translate that binary data into a human-readable format (as in the hard copy of the appendix). To transfer it digitally in the human readable form would still require specialist, bespoke software to make sure the values were not corrupted in translation (ASCII or EBCDIC? MSB or LSB?), and the internal RAM capacity of even high-end business machines may not have been enough to process the data in one pass, let alone manipulate it.
Wouldn't it be a waste of valuable capacity to record GMT with a resolution of one second when 1 minute is sufficient because the seconds can be derived from the frame count?
Indeed, and I think with today's level of technology in everyday use it's easy to lose sight of the fact that the growth in storage capacity and processing power is not linear, but practically exponential. The example I use is of my current cellphone, which is two years old and even back then was considered only modestly powerful, yet it has more raw processing power and storage capacity than the state-of-the-art desktop PC I built for my own use in 2002 - i.e only a little more than a decade ago, and almost a decade and a half after Habsheim. Extending that analogy, a decade before Habsheim computers were the size of a room, and reel-to-reel tape was the preferred storage medium if you were lucky - some were still using punch cards!