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20021023: 20021023: converting GINI composite radar image values to dbZ


David,

Correct. Forgot to mention the units bytes and the scaling by 10000.

The $NAWIPS/unidata/programs/nex2gini program I created uses the
data blocks in the $GEMTBL/unidata/nex2gini.tbl file for
the varous "stretch" sections. In the case of N0R, there is only 1
calibrated range. For, N1P there are 3 (because the LevelIII 
bins for the data range are much larger at the high end and the
difference between ND and "0.00"). 

The table I'm using currently looks like:
!
!
!Prod   band ncal units,Calval_1;....;calval_n  Prod_header
N0Z       25    1 dBZ,0,255,0,75            TICZ99 CHIZ
NET       26    1 KFt,0,255,0,85             TICZ99 CHIZ
N0R       27    1 dBZ,0,105,-30,75           TICZ99 CHIZ
NCR       28    1 dBZ,0,105,-30,75           TICZ99 CHIZ
NVL       29    1 Kg/m**2,0,255,0,85         TICZ99 CHIZ
N1P       30    3 inches,10,110,0,2;110,210,2,6;210,255,6,12      TICZ99 CHIZ
NTP       31    3 inches,10,110,0,4;110,220,4,12;210,255,12,24     TICZ99 CHIZ

Steve Chiswell
Unidata User SUpport


>From: "David Wojtowicz" <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200210232255.g9NMtTp06497

>
>----- Original Message -----
>From: "Unidata Support" <address@hidden>
>To: <address@hidden>
>Cc: <address@hidden>
>Sent: Wednesday, October 23, 2002 4:58 PM
>Subject: 20021023: converting GINI composite radar image values to dbZ
>
>
>>
>> David,
>>
>> I provide a calibration block in the image (in the unused portion
>> of the GINI header) that is used to obtain the image calibration bar
>> values.
>>
>> I created a section of code in $GEMPAK/source/gemlib/im/imgi2gm.f
>> with:
>> C
>> C*      Get calibration Block if it exists.
>> C*      Currently, only Unidata calibrations exist, using
>> C*          Word 47 = 128
>> C*      to signal that a calibration block is present.
>> C
>> At present the format is the number of calibration ranges N, followed by
>> N * 4 values where each set of 4 represents the pixel min, max and
>> data value min max they corespond to.
>>
>Steve thanks for the info.
>
>I was a bit confused at first, but it looks like starting at Octet 48, there
>is:
>
> 1) a space padded 8 byte character array with the name of the units
> 2) followed by a 1 byte size, N
> 3)  followed by N*4 4-byte values (words) that correspond to the values you
>mention above that are multiplied by 10000
>
>Is this the correct interpretation of the Unidata calibration section?
>
>Thanks!
>