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20030206: NEXRAD calibration information for raw values of zero



>From:  Rick Kohrs <address@hidden>
>Organization:  SSEC
>Keywords:  200302061458.h16EwY624125 McIDAS nexradir nexraget

Rick,

>Inquiry 11731 says that a raw value of 0 for PRCIPTOT gives a value of 
>09997.00.

The 9997 value is a missing data indicator.  There are two types of
"zero" values: values that are actually zero, and missing data.
I chose to indicate missing data values in the exact same way that
they are represented in the NEXRAD images themselves.

>I looked at all the different calibrated values for a raw value of 0 and 
>all of them give strange results (see attachment).

I don't have time tonight to repeat your extensive examination.
I did, however, check out the base reflectivities at tilts 0 and
1 as a quick check, and get different results:

N0R is the base reflectivity at tilt 0

IMGDISP RTNEXRAD/N0R ID=FTG LINELE= 230 230 PLACE=C MAG= 1 1 EU=BREF SU=X 
ALL=11 SF=YES REFRESH='EG GRA=(GRA);MAP FILE=OUTLUSAM MCOL=1 WID=1 
GRA=(GRA);BAR (GRA) SU=X X COL=7 ORIENT=VER;TE ?LASTFRM (GRA)'

     Image Name       ID       Day      Nominal Time   Scan Time    Band
  ----------------    ---    -------    ------------   ---------    ----
  RTNEXRAD/N0R        FTG  7 Feb 03038   01:30:00      MISSING       1

                        File     Nominal  Image     RAW     BRIT    ECHO    VIP
       Lat/Lon      Line/Element  Line/Element                      DBZ
 41:22:34 / 106:15:25   52/   86      53/   87         0         0  -9997      0

IMGPROBE: Done


IMGDISP RTNEXRAD/N1R ID=FTG LINELE= 230 230 PLACE=C MAG= 1 1 EU=BREF SU=X 
ALL=11 SF=YES REFRESH='EG GRA=(GRA);MAP FILE=OUTLUSAM MCOL=1 WID=1 
GRA=(GRA);BAR (GRA) SU=X X COL=7 ORIENT=VER;TE ?LASTFRM (GRA)'

     Image Name       ID       Day      Nominal Time   Scan Time    Band
  ----------------    ---    -------    ------------   ---------    ----
  RTNEXRAD/N1R        FTG  7 Feb 03038   01:30:00      MISSING       1

                        File     Nominal  Image     RAW     BRIT    ECHO    VIP
       Lat/Lon      Line/Element  Line/Element                      DBZ
 40:28:08 / 105:56:18  153/  111     154/  112         0         0  -9997      0

IMGPROBE: Done

In these two cases at least, the output from 'D' is what I intended.

>Also notice that some of the calibrated units are not given a name or a 
>unit.

In my two quick tests, I did not see this.

>Tom I think you and Russ wrote this calibration module, so can you shed 
>light on my findings?

I wrote the calibration stuff in the NEXRAD server, so Russ is not to
blame if there is a problem :-)

I will make a more systematic investigation along the lines of what you
did and see if I can replicate your results (e.g., lack of units
displayed).  I will reiterate, however, that the huge negative values
like -9997 are missing data indicators and need to stay as they are.

Tom

>--------------080504070803020809030006
>Content-Type: text/plain;
> name="Nexrad.out"
>Content-Transfer-Encoding: 7bit
>Content-Disposition: inline;
> filename="Nexrad.out"
>
>  NEXRAD/TOPS
>       Lat/Lon      Line/Element  Line/Element                      K FT
> 29:13:14 / 95:46:44    64/   40      65/   41         0         0    243
>
>  NEXRAD/SRVEL4 
>       Lat/Lon      Line/Element  Line/Element
> 29:25:37 / 95:13:24   234/  215     235/  216         0         0  -9997
>
>  NEXRAD/SRVEL3   
>       Lat/Lon      Line/Element  Line/Element
> 29:24:33 / 95:12:09   236/  217     237/  218         0         0  -9997
>
>  NEXRAD/SRVEL2  
>       Lat/Lon      Line/Element  Line/Element
> 29:22:23 / 95:10:18   240/  220     241/  221         0         0  -9997
>
>  NEXRAD/SRVEL1 
>       Lat/Lon      Line/Element  Line/Element
> 29:28:19 / 95:05:21   229/  228     230/  229         0         0  -9997
>
>  NEXRAD/PRECIPTOT
>       Lat/Lon      Line/Element  Line/Element                      IN
> 29:28:19 / 95:05:58   114/  114     115/  115         0         09997.00
>
>  NEXRAD/PRECIP1 
>       Lat/Lon      Line/Element  Line/Element                      IN
> 29:28:19 / 95:05:58   114/  114     115/  115         0         09997.00
>
>  NEXRAD/CREF   
>       Lat/Lon      Line/Element  Line/Element                      DBZ
> 29:24:00 / 95:22:03   239/  203     240/  204         0         0  -9997     
>  0
>
>  NEXRAD/BVEL2 
>       Lat/Lon      Line/Element  Line/Element
> 29:24:00 / 95:22:03   237/  201     238/  202         0         0  -9997
>
>  NEXRAD/BVEL1
>       Lat/Lon      Line/Element  Line/Element
> 29:24:00 / 95:22:03   237/  201     238/  202         0         0  -9997
>
>  NEXRAD/BREF4  
>       Lat/Lon      Line/Element  Line/Element                      DBZ
> 29:24:00 / 95:22:03   237/  201     238/  202         0         0  -9997     
>  0
>
>  NEXRAD/BREF3 
>       Lat/Lon      Line/Element  Line/Element                      DBZ
> 29:24:00 / 95:22:03   237/  201     238/  202         0         0  -9997     
>  0
>
>  NEXRAD/BREF2
>       Lat/Lon      Line/Element  Line/Element                      DBZ
> 29:24:00 / 95:22:03   237/  201     238/  202         0         0  -9997     
>  0
>
>  NEXRAD/BREF1 
>       Lat/Lon      Line/Element  Line/Element                      DBZ
> 29:24:00 / 95:22:03   237/  201     238/  202         0         0  -9997     
>  0
>
>  NEXRAD/BREF248 
>       Lat/Lon      Line/Element  Line/Element                      DBZ
> 29:19:42 / 95:39:21   237/  201     238/  202         0         0  -9997     
>  0
>
>  NEXRAD/VIL    
>       Lat/Lon      Line/Element  Line/Element
> 29:00:17 / 96:03:54    70/   33      71/   34         0         0    243
>
>--------------080504070803020809030006--
>
--
+-----------------------------------------------------------------------------+
* Tom Yoksas                                             UCAR Unidata Program *
* (303) 497-8642 (last resort)                                  P.O. Box 3000 *
* address@hidden                                   Boulder, CO 80307 *
* Unidata WWW Service                             http://www.unidata.ucar.edu/*
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