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Re: Snapshot of US National Airspace Data CD-ROM
On Wed, Dec 15, 1999 at 08:17:02PM -0500, A. Reichert wrote:
>
> I may be able to help with the FTP availability. (1) What is the total
> size,
See below...
>and (2) can you tell me for certain that there is no copyright
> problems?
>
> - Alan
>
Will check on this...
I tried compressing the "raw" NASD fixed length record data files.
The original files are indeed pretty BIG (total > 245 MB). The good
news is that I found out they will compress much better than I had first
guessed. They compress to as little as roughly 3% of the original size
(using bzip2 compression). I calculated a histogram of the "apt.txt"
file and found that 87.3% of the characters are blanks, so these ratios
are not too surprising in view of that. Using bzip2, all the data is
less than 8 MB! Here's the nitty-gritty:
gzip compression stats:
no compression gzip -1 gzip -9
============== ======= =======
aff.txt: 1492194 172587 137010
apt.txt: 102171238 8268917 6638055
arb.txt: 905848 52475 33527
awy.txt: 9074325 1140017 821790
com.txt: 1016090 91096 72156
fix.txt: 36673780 1514892 1110183
fss.txt: 2756449 101375 80508
hpf.txt: 7819728 810756 645089
ils.txt: 1929194 287609 228867
lid.txt: 23571135 1040744 725685
mtr.txt: 14525280 930474 707117
nav.txt: 6753480 618244 490246
oth.txt: 2632531 333050 226927
pfr.txt: 11299865 421894 301844
pja.txt: 462324 49602 40023
ssd.txt: 1578654 212855 162090
sua.txt: 7024368 319831 215716
twr.txt: 13074432 705387 526279
wxl.txt: 289419 68318 57680
---------- ---------- ----------
Totals 245050334 17140123 13220792
Ratios 6.99453 % 5.3951 %
bzip2 compression stats:
no compression bzip2 -1 bzip2 -9
============== ======== ========
aff.txt: 1492194 131997 121245
apt.txt: 102171238 4647535 3735390
arb.txt: 905848 24679 23231
awy.txt: 9074325 578409 497476
com.txt: 1016090 46222 39982
fix.txt: 36673780 580053 539569
fss.txt: 2756449 54133 46939
hpf.txt: 7819728 373526 284158
ils.txt: 1929194 190893 172369
lid.txt: 23571135 430320 361081
mtr.txt: 14525280 451197 387903
nav.txt: 6753480 359318 326460
oth.txt: 2632531 164553 159021
pfr.txt: 11299865 203243 165497
pja.txt: 462324 32111 30434
ssd.txt: 1578654 135968 118388
sua.txt: 7024368 130183 110767
twr.txt: 13074432 365681 310752
wxl.txt: 289419 44735 43638
---------- ---------- ----------
Totals 245050334 8944756 7474300
Ratios 3.65017 % 3.05011 %
--
___|___ | John C. Peterson, KD6EKQ | Try Linux for Intel x86, it's the
-(*)- | mailto:jaypee@netcom.com | Ferarri of 32 bit operating systems!
o/ \o | San Diego, CA U.S.A | See http://www.linux.org/ for info
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