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20010409: time issues in meteosat imagery (cont.)



>From: address@hidden (Chris Hennon)
>Organization: Ohio State University
>Keywords: 200104061848.f36ImGL26255 McIDAS METEOSAT time

Chris,

>I'm a bit confused.....

Join the club :-)

>I created a script that does the job with no problem, but it appears that
>the IMGCHA command doesn't actually change the time???
>
>IMGLIST METSAT-7.ALL DAY=98313
>Image file directory listing for:METSAT-7
> Pos Satellite/         Date       Time      Center   Band(s)
>     sensor                                 Lat  Lon
> --- -------------  ------------  --------  ---- ---- ------------
> 155  METEOSAT7      9 NOV 98313  06:00:00     0    0 8
> 156  METEOSAT7      9 NOV 98313  12:00:00     0    0 8
> 157  METEOSAT7      9 NOV 98313  18:00:00     0    0 8
> 158  METEOSAT7      9 NOV 98313  24:00:00     0    0 8
>IMGLIST: done
>
>IMGCHA METSAT-7.158 TIME=00:00:00
>
>     Directory Block Changes
>Changed Image Time from: 240000  to: 0
>
>Transferring AREA data outbound, bytes= 336
>
>Image file directory listing for:METSAT-7
> Pos Satellite/         Date       Time      Center      Res (km)
>Image_Size
>     sensor                                 Lat  Lon    Lat   Lon
> --- -------------  ------------  --------  ---- ----  ----- -----
>------------
> 158  METEOSAT7      9 NOV 98313  24:00:00     0    0
>    Band: 8  11.5 um Nighttime cloud detection           5.0   5.0  2500 x
>2500
>     proj:    0 created: 2001067  35443  memo: METEOSAT
>     type:MSAT     cal type:RAW
>     offsets:  data=     768 navigation=  256 calibration=    0 auxillary=
>0
>     doc length:   0   cal length:   0   lev length:   0 PREFIX=   0
>     valcod:          0 zcor:  1 avg-smp: A
>     lcor:    1  ecor:     1  bytes per pixel: 1  ss: 58
>     Image Center Point Res (derived)  Lat:   4.52 (km)  Lon:   4.49 (km)
>
>IMGLIST: done
>IMGCHA: Done ...
>
>Looks like something happened, but I don't know what. Any ideas?  Thanks.

One of two things may be happening:

o the image might not be writable by the IMGCHA process you are running

o IMGCHA is can not change the time in the image because the time doesn't
  represent a valid time in McIDAS

In order to test the second possibility, I copied an image from a server
to make it local and then changed the time in it to 24:00:00:

DATALOC ADD RTIMAGES ADDE.UCAR.EDU
IMGCOPY RTIMAGES/GE-WV MYDATA/IMAGES.2001 SIZE=ALL
Beginning Image Data transfer, bytes= 607856
Transferring AREA data outbound, bytes= 607936
IMGCOPY: RTIMAGES/GE-WV.316 copied to MYDATA/IMAGES.2001
IMGCOPY: done

IMGLIST MYDATA/IMAGES.2001
Image file directory listing for:MYDATA/IMAGES
 Pos Satellite/         Date       Time      Center   Band(s)

     sensor                                 Lat  Lon
 --- -------------  ------------  --------  ---- ---- ------------
2001  G-8 IMG        9 APR 01099  21:15:00    23   71 3
IMGLIST: done

LWU LIST AREA2001 0 10
       0.          0           4 HEX:        0        4 ASCII:
       2.         70      101099 HEX:       46    18AEB ASCII:    F
       4.     211500        2789 HEX:    33A2C      AE5 ASCII:   :,
       6.       9209           0 HEX:     23F9        0 ASCII:   #
       8.        700         864 HEX:      2BC      360 ASCII:         `
      10.          1           0 HEX:        1        0 ASCII:
 --END OF LISTING

LWU POKE AREA2001 240000 4
 Value was:       211500 HEX:        33A2C ASCII:   :,

IMGLIST MYDATA/IMAGES.2001
Image file directory listing for:MYDATA/IMAGES
 Pos Satellite/         Date       Time      Center   Band(s)
     sensor                                 Lat  Lon
 --- -------------  ------------  --------  ---- ---- ------------
2001  G-8 IMG        9 APR 01099  24:00:00    23   71 3
IMGLIST: done

IMGCHA MYDATA/IMAGES.2001 TIME=00:00:00

     Directory Block Changes
Changed Image Time from: 240000  to: 0
Transferring AREA data outbound, bytes= 656
Image file directory listing for:MYDATA/IMAGES
 Pos Satellite/         Date       Time      Center      Res (km)   Image_Size
     sensor                                 Lat  Lon    Lat   Lon
 --- -------------  ------------  --------  ---- ----  ----- ----- ------------
2001  G-8 IMG        9 APR 01099  00:00:00    23   71
    Band: 3   6.8 um Upper level water vapor             8.0  16.0   700 x  864
     proj:    0 created: 2001099 215839  memo: RT GVAR
     type:VISR     cal type:BRIT
     offsets:  data=    2816 navigation=  256 calibration=    0 auxillary=    0
     doc length:   0   cal length:   0   lev length:   0 PREFIX=   0
     valcod:          0 zcor:  0 avg-smp: N
     start yyddd: 2001099  start time:211515  start scan:  401
     lcor: 2789  ecor:  9209  bytes per pixel: 1  ss: 70
     Image Center Point Res (derived)  Lat:   9.17 (km)  Lon:   9.34 (km)

IMGLIST: done

IMGCHA: Done ...

My conclusion from this sequence is that IMGCHA _can_ change a time of
24:00:00 to 00:00:00.  This says that the only thing left (if my original
list of possibilities is correct) is that the image(s) you are trying
to change are not writable.  Unfortunately, IMGCHA doesn't come back and
tell you of the error.  The reason for this is buried too deep in the
history of McIDAS, so I will leave it.

So, check the write permissions on your METEOSAT images and make sure
that you (you from your McIDAS session) can write to them.  A real quick
way of finding this out is to run the IMGLIST and LWU sequences above
and see if the file gets changed.

Tom


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