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CLAI and CTH file header contents...


David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

Folks, by inspection, the file headers for this data are as shown
below. At present, I am converting the lower 6 bits of CTH into a
greyscale (0..252) and adding in the two most significant bits of
the data (fog and height quality) as the two lowest bits of the
image. I guess this produces something like what you are used to
seeing.

CTH
--------------------------------
_NAME:=Fog indicator
0:=No fog
1:=Fog in CTH segment

$DISCRETE:=1
_NAME:=Height quality indicator
0:=Height quality OK
1:=Height quality poor

$HALFTONE:=6
_NAME:=Cloud top height
_UNIT:=Metres
1:=00
63:=18600
--------------------------------


I wasn't as sure how to handle CLAI! Clearly there isn't really
anything which is "image" data as such, so I'm just doubling the
data to make 0..110 scale to an image with 0..220. Perhaps we need
to look at colur palettes to interpret the data further. What
amateurs get of MPEF once the trial is over is not known, so I don't
see it as a high priority right now. If you have time, experiment!

CLAI
--------------------------------
_NAME := Scene type
0:=No scene identified; missing input data
1:=Evergreen needleleaf forest
2:=Evergreen broadleaf forest
3:=Deciduous needleleaf forest
4:=Deciduous broadleaf forest
5:=Mixed deciduous forest
6:=Closed shrubland
7:=Open shrubland
8:=Woody savannah
9:=Savannah
10:=Grassland
11:=Permanent wetland
12:=Cropland
13:=Urban
14:=Crop/natural vegetation mosaic
15:=Permanent snow/ice
16:=Barren/desert
17:=Water bodies
18:=Tundra
97:=Snow/ice over land
98:=Snow/ice over water
99:=Clear sunlight
101:=Low-level cloud; Fog or Stratus
102:=Low-level cloud; Cumulus or Stratocumulus
103:=Low-level cloud; unknown type
104:=Mid-level cloud; Nimbostratus
105:=Mid-level cloud; Altocumulus or Altostratus
106:=Mid-level cloud; unknown type
107:=High-level cloud; Cumulonimbus
108:=High-level cloud; Cirrus
109:=High-level cloud; unknown type
110:=Unknown cloud type
--------------------------------


Douglas Deans <douglas@...>
 

----- Original Message -----
From: "David Taylor" <david-taylor@...>
To: <MSG-1@...>
Sent: Thursday, October 23, 2003 9:25 AM
Subject: [MSG-1] CLAI and CTH file header contents...


Folks, by inspection, the file headers for this data are as shown
below. At present, I am converting the lower 6 bits of CTH into a
greyscale (0..252) and adding in the two most significant bits of
the data (fog and height quality) as the two lowest bits of the
image. I guess this produces something like what you are used to
seeing.

I wasn't as sure how to handle CLAI! Clearly there isn't really
anything which is "image" data as such, so I'm just doubling the
data to make 0..110 scale to an image with 0..220. Perhaps we need
to look at colur palettes to interpret the data further. What
amateurs get of MPEF once the trial is over is not known, so I don't
see it as a high priority right now. If you have time, experiment!
At the moment for amateur use, and anyway until we all become familiar with
the data, what you are doing with CTH and CLAI sounds spot on.
I rechecked a copy I had kept of my MSG registration form, and contrary to
what I incorrectly said in a mail yesterday, MPEF is not mentioned. So
there is no option to ask for it or not. MDD is mentioned as only for the
professionals (or words to that effect).
I do hope it will continue to be available and the lack of option makes me
hopeful, particularly as CTH was offered in wefax.

Further to our direct mails everything is still working fine with beta 251.
Again thanks for you very hard work so late at night !

Thanks
Douglas.