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20021026: Unidata lossless PNG compression of NOAAPORT image products (correction)



>From:  "Thomas Renkevens" <address@hidden>
>Organization:  NOAA
>Keywords:  200210181813.g9IIDJ102051 NOAAPORT GINI compress

Tom, Fred, Kevin,

Oops.  The standard deviation numbers I sent in my last email were
actually variances (std**2).  The list below contains the correct
standard deviations.

I finally was able to free up enough time to compile some statistics on
the lossless PNG technique we use to compress NOAAPORT GINI images we
send in our IDD.

The following numbers represent NOAAPORT GINI imagery received between
23 Z Friday, October 25 to 23 Z Saturday, October 26.  We compress the
images received in NOAAPORT before injecting them into our IDD.  The
compressed images are uncompressed upon receipt at downstream hosts.

                      PNG Compression
GINI Product          Mean   Std     Product Description
---------------------+------+-------+------------------------
AK-NATIONAL_VIS       2.285  0.352   Alaska Nat 8 km  0.65 um
AK-NATIONAL_WV        6.911  0.795   Alaska Nat 8 km  6.8  um
AK-NATIONAL_IR        3.001  0.409   Alaska Nat 8 km 10.7  um
AK-REGIONAL_VIS       1.718  0.162   Alaska Reg 2 km  0.65 um
AK-REGIONAL_3.9       1.962  0.040   Alaska Reg 8 km  3.9  um
AK-REGIONAL_WV        3.576  0.057   Alaska Reg 16km  6.8  um
AK-REGIONAL_IR        2.077  0.024   Alaska Reg 8 km 10.7  um
AK-REGIONAL_12.0      2.085  0.025   Alaska Reg 8 km 12.0  um
HI-NATIONAL_VIS       3.599  0.865   Hawaii Nat 14km  0.65 um
HI-NATIONAL_WV        8.813  2.105   Hawaii Nat 14km  6.8  um
HI-NATIONAL_IR        4.377  1.006   Hawaii Nat 14km 10.7  um
HI-REGIONAL_VIS       1.878  0.257   Hawaii Reg 1 km  0.65 um
HI-REGIONAL_3.9       2.616  0.375   Hawaii Reg 4 km  3.9  um
HI-REGIONAL_WV        3.947  0.511   Hawaii Reg 8 km  6.8  um
HI-REGIONAL_IR        2.688  0.342   Hawaii Reg 4 km 10.7  um
HI-REGIONAL_12.0      2.656  0.333   Hawaii Reg 4 km 12.0  um
PR-NATIONAL_VIS       2.341  0.922   P Rico Nat 8 km  0.65 um
PR-NATIONAL_WV        5.401  1.921   P Rico Nat 8 km  6.8  um
PR-NATIONAL_IR        2.920  1.172   P Rico Nat 8 km 10.7  um
PR-REGIONAL_VIS       2.159  0.533   P Rico Reg 1 km  0.65 um
PR-REGIONAL_3.9       2.858  0.756   P Rico Reg 4 km  3.9  um
PR-REGIONAL_WV        4.049  1.070   P Rico Reg 8 km  6.8  um
PR-REGIONAL_IR        2.918  0.781   P Rico Reg 4 km 10.7  um
PR-REGIONAL_12.0      2.896  0.763   P Rico Reg 4 km 12.0  um

                      PNG Compression
GINI Product          Mean   Std     Product Description
---------------------+------+-------+------------------------
EAST-CONUS_VIS        1.947  0.173   East Conus 1 km  0.65 um
EAST-CONUS_3.9        2.203  0.069   East Conus 4 km  3.9  um
EAST-CONUS_WV         4.274  0.083   East Conus 8 km  6.8  um
EAST-CONUS_IR         2.544  0.974   East Conus 4 km 10.7  um
EAST-CONUS_12.0       2.515  0.054   East Conus 4 km 12.0  um
WEST-CONUS_VIS        1.857  0.113   West Conus 1 km  0.65 um
WEST-CONUS_3.9        2.295  0.052   West Conus 4 km  3.9  um
WEST-CONUS_WV         4.391  0.109   West Conus 8 km  6.8  um
WEST-CONUS_IR         2.518  0.082   West Conus 4 km 10.7  um
WEST-CONUS_12.0       2.487  0.069   West Conus 4 km 12.0  um

                      PNG Compression
GINI Product          Mean   Std     Product Description
---------------------+------+-------+------------------------
NHEM-COMP_VIS         1.760  0.161   Nth Hemi   24km  0.65 um
NHEM-COMP_3.9         2.011  0.133   Nth Hemi   24km  3.9  um
NHEM-COMP_WV          3.429  0.245   Nth Hemi   24km  6.8  um
NHEM-COMP_IR          1.983  0.136   Nth Hemi   24km 10.7  um
NHEM-COMP_12.0        2.013  0.138   Nth Hemi   24km 12.0  um
NHEM-MULTICOMP_VIS    2.050  0.139   MultiSat   24km  0.65 um
NHEM-MULTICOMP_WV     2.809  0.111   MultiSat   24km  6.8  um
NHEM-MULTICOMP_IR     1.815  0.019   MultiSat   24km 10.7  um
SUPER-NATIONAL_VIS    1.583  0.018   SuprNatnl  8 km  0.65 um
SUPER-NATIONAL_3.9    1.959  0.040   SuprNatnl  8 km  3.9  um
SUPER-NATIONAL_WV     4.286  0.044   SuprNatnl  8 km  6.8  um
SUPER-NATIONAL_IR     2.051  0.019   SuprNatnl  8 km 10.7  um
SUPER-NATIONAL_12.0   2.073  0.018   SuprNatnl  8 km 12.0  um
SUPER-NATIONAL_CTP    6.148  0.703   SuprNatnl  8 km Cld Top Pres
SUPER-NATIONAL_LI     6.853  0.823   SuprNatnl  8 km Lifted Index
SUPER-NATIONAL_PW     6.789  0.818   SuprNatnl  8 km Precip Water
SUPER-NATIONAL_SFC-T  6.463  0.761   SuprNatnl  8 km Sfc Temp

As a comparison, the same numbers for various composites we create from
the NOAAPORT NEXRAD level III products is:

                      PNG Compression
GINI Product          Mean   Std     Product Description
---------------------+------+-------+------------------------
RADAR_n0r             9.248   1.611  1 km N0R composite
RADAR_n1p            63.142   5.198  2 km N1P composite
RADAR_ntp            13.549   1.075  4 km NTP composite

Values in the 'Mean' column represent the average compression ratio
over the 24 hour ingest period, and values in the 'Std' column
represent the standard deviation of those compression ratios.

As you would expect for satellite imagery, VIS images compress the
least and water vapor compress the most.  Compression ratios for
satellite products (e.g., CTP, LI, PW, and SFC-T) are all good.

I hope these numbers are useful.

Tom

>From address@hidden Mon Oct 28 05:25:39 2002
>CC: Frederick R Mosher <address@hidden>,
>   Kevin Schrab <address@hidden>, address@hidden
>Subject: Re: 20021021: Unidata lossless PNG compression of NOAAPORT image 
>products

Awesome! Thanks for the numbers and I will pass this information around.
Tom