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[McIDAS #ZNQ-188340]: Displaying SST via L2 GOES-16 Products



Hi Carol,

re:
> I'm trying to display the GOES-16 L2 SST product over the Carribean. See
> the attached image to witness my first go at this.

OK.  I just created a display like yours.

re:
> First, I created the various L2 datasets via desserve using ABIN as the
> format. It seems like that was the correct format to use based on the User
> Guide
> <https://www.ssec.wisc.edu/mcidas/doc/users_guide/current/dsserve.html> 
> section
> about the GOES-R series.

Depending on the version of McIDAS you are running, ABIN would be correct.

re:
> So I'm getting confused based on what to use for the EU and SU commands. I
> see that there is a L2-SST.ET and SST.ST which I figured I could use.

The enhancement L2-SST.ET is correct.  The stretch table SST.ST might
be wrong since it was crated for the old SST product that was distributed
before the GOES-R series of satellites.

re:
> Unfortunately, it seems like something isn't getting translated properly in
> the units of the BAR. I don't think the SST values range from 3-255 K.......
> 
> Here are the commands I'm running to get this plot. I couldn't get the SU
> to work....
> 
> imgremap.k RTGOESR/L2FDSST MYDATA/AREAS.10 TIME=15:00:19 LATLON=20 75
> PRO=MERC RES=2.5 SIZE=1024 1600 SSIZE=ALL BAND=25
> imgdisp.k MYDATA/AREAS.10 MAG= EU=L2-SST.ET SU=X
> map.k X 1 FILE=OUTLUSAM WID=2
> map.k X 1 FILE=OUTLHPOL WID=2
> bar.k X COLOR=2 SU=X
> 
> When running with the SU=SST, it can't find the correct units.
> 
> imgdisp.k MYDATA/AREAS.10 MAG= EU=L2-SST.ET SU=SST
> imgdisp.k: Units requested are not available for this image
> imgdisp.k: done

This is undoubtedly being caused by using a stretch table that
was created for a previous incarnation of SST images where the
calibrated unit was degK.

You can see what the calibrated unit of the image you displayed
is by:

- IMGDISP the image
- move the cursor over an interesting feature
- run the D command (e.g., D<return> or CTRL-D)

I just did this and got the following output:

     Image Name           Day      Nominal Time   Scan Time    Band
  ----------------      -------    ------------   ---------    ----
  NPGOESR/SSTFD.96    13 Apr 21103   16:00:19      16:03:24      25

                        File     Nominal  Image     RAW         SST         BRIT
       Lat/Lon      Line/Element  Line/Element                  K
 16:26:18/ 74:08:29   1824/ 2757    7297/11029          47918      297.00       
  185

IMGPROBE: Done

So, the unit of the GOES-16 L2 SST product is 'K', not 'degK'.

re:
> I really haven't worked directly with stretch tables very much, so there
> could be something that I'm totally missing.

A new stretch table should be made and used with the GOES-16 L2 SST
images.

Here is what to try:

IMGLIST NPGOESR/SSTFD FORM=ALL
Image file directory listing for:NPGOESR/SSTFD
 Pos Satellite/         Date       Time      Center      Res (km)   Image_Size
     sensor                                 Lat  Lon    Lat   Lon
 --- -------------  ------------  --------  ---- ----  ----- ----- ------------
  96  GOES-16 L2    13 APR 21103  16:00:19     0   75
   Band: 25   L2: SST  - Sea Surface Temperature        2.02  2.00  5424 x 5424
     proj:    0 created: 2021103 160019  memo: GOES Full Disk - Mode 6
     type:ABIN     cal type:RAW
     offsets:  data=     768 navigation=  256 calibration=  768 auxiliary=  768
     doc length:   0   cal length:   0   lev length:   0 PREFIX=   0
     valcod:          0 zcor:  0 avg-smp: N
     lcor:    1  ecor:     1  bytes per pixel: 2  ss:187
     Resolution Factors (base=1):   Line=    4.0   Element=    4.0
IMGLIST: done

This shows that 'type' is ABIN.

HELP SU
SU -- Image data stretching utility
   SU INI name type unit <keywords>
   SU MAKE name inlo inhi britlo brithi
   SU LIST string
   SU TABLE name
Parameters:
   INI | initializes the stretch table defining the type of calibration,
         calibration units and initial breakpoint settings; must be done
         for making a new stretch table
   MAKE | enters breakpoints in the table using brightness levels
   LIST | lists the stretch tables saved on the workstation (def)
   TABLE | lists the breakpoints stored in a stretch table
   name | name of stretch table; 8 characters maximum
   string | list only stretch tables beginning with this character string
   type | calibration type for the input table (def=any calibration type);
          to find the calibration type of an image, run IMGLIST FORM=ALL
          and see the value for "type" in the output
   unit | calibration units for the input table; valid units are RAW,
          BRIT, RAD, TEMP, ALB or user-defined units; use command IMGPROBE
          or D to list available units for an image (def=BRIT)
   inlo | low value of the breakpoint for input values; specify in units
          input with the 'unit' parameter
   inhi | high value of the breakpoint for input values; specify in units
          input with the 'unit' parameter
   britlo | low values of the breakpoints for output brightness values;
            the range is 0-255
   brithi | high values of the breakpoints for output brightness values;
            the range is 0-255
 ...

1) create a new, empty stretch table

   SU INI L2-SST ABIN SST

2) define a mapping between calibrated unit and brightnesses
 
   SU MAKE LW-SST 270 307 3 251

   NB: you can create any mapping that you want.  The most logical
   thing (to me, at least) is to sample values in the full range of
   brightnesses and use those values for the mapping.  The values
   I used here simply mimic the values in the existing SST.ST
   stretch table.

3) list out the values in the stretch table just created: 

SU TABLE L2-SST
BREAKPOINTS STORED IN TABLE : L2-SST.ST
INPUT       OUTPUT
-----       ------
 270           3
 307           251
CALIBRATION TYPE  : ABIN
CALIBRATION UNITS : K
BAND NUMBER       : -1
INTERPOLATION TYPE: LIN
SU: DONE

4) specify the use of the L2-SST.ST stretch in a BAR command and/or
   in the IMGDISP you are using to display the image

Please let me know if/when you have questions.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: ZNQ-188340
Department: Support McIDAS
Priority: Normal
Status: Closed
===================
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