Re: US National Airspace Data CD-ROM - ATA-120

["D.F.S." <dfs@xmission.com>]

> 
> On Mon, Jan 24, 2000 at 12:06:48PM -0700, D.F.S. wrote:
> > So did we ever come up with a way and place to post this on the 
> > web, ftp site or at the very least distribute it within the list?
> > 
> > I'll order the CD if necessary.
> > 
>     I think we are waiting for someone to offer to provide the
> resources required. The files are way too large to post to the
> list, we would need an http or ftp server with good connectivity.
> If the files are compressed with "gzip -9", the storage resources
> required are about 14 Mb, with "bzip2 -9" about 8 Mb.  (I posted a
> detailed summary of various commpression methods on Wed, Dec 15,
> 1999).

As an aside related to compression.

Recently as part of a quest to enable backups spooled data I went
looking for a better compression program.

In this case "Better" was faster.

I was spooling ~36 gigabytes of data off to a disk for later 
writing to tape.

Gzip and Compress was taking ~7-8 hours

A straight file copy took 1 hr 10 minutes.

I got a copy of a C library that does compression Lzo If I recall.
It is designed for realtime compression use.
There is a small subset library that is about 16K.

I got a gzip compatible program based on that library as well.

That program copied and compresses the files in just under 2 hours.

It generated files ~5% larger than the Gzip files.

Changing the files from a fixed length format should save a bunch
of space, but in addition, using a compression library to
process them on the fly could have real advantages.

Esp. if we are talking embedded type machines.

I consider a $50.00 laptop stuffed under a seat and the screen velcro'd
to the panel "Embedded" in this case.

Marc

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