[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Datastream #SXB-674928]: GOES East West imagery...
- Subject: [Datastream #SXB-674928]: GOES East West imagery...
- Date: Wed, 04 Feb 2015 16:55:20 -0700
Hi Gilles,
re:
> I tired as you mentioned by loading West, then East (before that I loaded
> the composite, disabled the Auto-set Projection...)
>
> Please find attached the images captured from 1) only West IR, 2) West and
> East IR, and 3) the East/West IR composite
>
> It seems the last one give a nicer result, at least more usable for the
> region of interest.
>
> What do you think?
Something looks wrong to me, or, if not wrong, not as good as it should be.
I say this be cause the pixel resolution in the individual GOES-East
and GOES-West IR sectors that we distribute in the IDD UNIWISC datastream
are higher in resolution than the East/West IR composite we distribute
in the same datastream. Here is the IMGLIST output from McIDAS-X that
illustrates
the difference in resolutions for the East and West images used in creation
of the East/West composite for 21:45 UTC today
IMGLIST RTIMAGES/GE-IR FORM=ALL TIME=21:30 21:59
Image file directory listing for:RTIMAGES/GE-IR
Pos Satellite/ Date Time Center Res (km) Image_Size
sensor Lat Lon Lat Lon
--- ------------- ------------ -------- ---- ---- ----- ----- ------------
95 G-13 IMG 4 FEB 15035 21:45:00 0 72
Band: 4 10.7 um IR Surface/Cloud-top Temp 4.03 4.59 2726 x 1732
proj: 0 created: 2015035 220047 memo: RT GVAR
type:VISR cal type:BRIT
offsets: data= 2816 navigation= 256 calibration= 0 auxiliary= 0
doc length: 0 cal length: 0 lev length: 0 PREFIX= 0
valcod: 0 zcor: 0 avg-smp: N
start yyddd: 2015035 start time:214519 start scan: 356
lcor: 2605 ecor: 9017 bytes per pixel: 1 ss:180
Resolution Factors (base=1): Line= 4.0 Element= 8.0
IMGLIST: done
IMGLIST RTIMAGES/GW-IR FORM=ALL TIME=21:30 21:59
Image file directory listing for:RTIMAGES/GW-IR
Pos Satellite/ Date Time Center Res (km) Image_Size
sensor Lat Lon Lat Lon
--- ------------- ------------ -------- ---- ---- ----- ----- ------------
95 G-15 IMG 4 FEB 15035 21:30:00 24 137
Band: 4 10.7 um IR Surface/Cloud-top Temp 4.64 4.66 1400 x 1740
proj: 0 created: 2015035 213801 memo: RT GVAR
type:VISR cal type:BRIT
offsets: data= 2816 navigation= 256 calibration= 0 auxiliary= 0
doc length: 0 cal length: 0 lev length: 0 PREFIX= 0
valcod: 0 zcor: 0 avg-smp: N
start yyddd: 2015035 start time:213019 start scan: 306
lcor: 2553 ecor: 8101 bytes per pixel: 1 ss:184
Resolution Factors (base=1): Line= 4.0 Element= 8.0
IMGLIST: done
IMGLIST RTIMAGES/GEW-IR FORM=ALL TIME=21:30 21:59
Image file directory listing for:RTIMAGES/GEW-IR
Pos Satellite/ Date Time Center Res (km) Image_Size
sensor Lat Lon Lat Lon
--- ------------- ------------ -------- ---- ---- ----- ----- ------------
95 G-13 IMG 4 FEB 15035 21:45:00 26 100
Band: 4 10.7 um IR Surface/Cloud-top Temp 10.72 9.14 592 x 1204
proj: 0 created: 2015035 220117 memo: GOES East-West Composite
type:VISR cal type:BRIT
offsets: data= 1280 navigation= 256 calibration= 768 auxiliary= 0
doc length: 0 cal length: 0 lev length: 0 PREFIX= 0
valcod: 0 zcor: 1 avg-smp: A
pdl: 0 0 0 1 0 0 0 1 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
start yyddd: 1996019 start time:160000 start scan: 2500
lcor: 91 ecor: 89 bytes per pixel: 1 ss:180
Resolution Factors (base=1): Line= 4.0 Element= 4.0
IMGLIST: done
The listings show that the resolution of the East and West images is nominally
4 km while the resolution of the composite is nominally 10 km. The size of
individual pixels in the attached West_IR_Only and W_and_E_IR are much larger
(meaning lower resolution) than for the EW_IR_Comp image captures you attached.
This strongly suggests that progressive resolution was in effect when you
displayed the West_IR_Only and W_and_E_IR images.
Please try experiment again, but this time:
- turn off adaptive resolution (from Dashboard -> Edit -> Preferences -> View)
and restart the IDV to make sure the preference change is active
- make sure to set the Magnification factors in the Advanced tab of the
Field Selector tab to 1 for all three of the image displays
You should observe the following for your area of interest:
1) the pixels shown will be from the last image loaded when loading both
GOES-East and GOES-West IR images
I.e., if you loaded GOES-West IR first and then GOES-East IR, then
the pixels shown will be the ones from GOES-East IR image; if you
loaded GOES-East first and then GOES-West, the pixels would be from
the GOES-West image.
It is up to you to choose which satellite's IR image is most representative
for the phenomena you are investigating. This may be a hard decision
depending on how widespread the phenomena you are investigating are
since your area of interest (which appears to be around 103W longitude)
is close to being as far from GOES-East as it is from GOES-West (GOES-East
is located at 75W and GOES-West is at 135W)
2) the size of the pixels in the display of first GOES-West then GOES-East
(or visa versa) will be much smaller (meaning higher resolution) than
the pixels from the East/West composite (~4 km vs ~10 km)
Higher resolution imagery should be better for the type of investigation
you (your student) is conducting.
In case you didn't already know, the East/West composite images are created
using pixels from GOES-East for longitudes <= 97:30W and from GOES-West for
longitudes >= 102:30W and a blend of the two for longitudes between 97:30W
and 102:30W. Since the scan time for the East sector is 15 minutes later
the scan time for the West sector (see the times indicated in the IMGLIST
listings above) used in the composite, the use of pixels from one satellite
on one side of the composite and from the satellite on the other side of the
composite can result in feature disconnections. This is the reason that I
chose to blend East and West pixel values in the 97:30W to 102:30 middle of
the composite (the composite's center is 100W).
** I hope that this description is not too confusing; please let me know if
it was !! **
Cheers,
Tom
--
****************************************************************************
Unidata User Support UCAR Unidata Program
(303) 497-8642 P.O. Box 3000
address@hidden Boulder, CO 80307
----------------------------------------------------------------------------
Unidata HomePage http://www.unidata.ucar.edu
****************************************************************************
Ticket Details
===================
Ticket ID: SXB-674928
Department: Support Datastream
Priority: Normal
Status: Closed