Hi people,
I used gdal_translate in the GRIB file I want to show with mapserver,
but there still is something wrong. The following is a partial output
from it:
Driver: GRIB/GRIdded Binary (.grb)
Files: data\raster\T126L28.grb
Size is *161, 98*
Coordinate System is:
.....
Origin = (-150.000000000000000,-61.246000000000002)
Pixel Size = (0.938000000000000,-0.001836734693878)
Corner Coordinates:
Upper Left (-150.0000000, -61.2460000) (150d 0'0.00"W, 61d14'45.60"S)
Lower Left (-150.0000000, -61.4260000) (150d 0'0.00"W, 61d25'33.60"S)
Upper Right ( 1.0180000, -61.2460000) ( 1d 1'4.80"E, 61d14'45.60"S)
Lower Right ( 1.0180000, -61.4260000) ( 1d 1'4.80"E, 61d25'33.60"S)
Center ( -74.4910000, -61.3360000) ( 74d29'27.60"W, 61d20'9.60"S)
Band 1 Block=*161x1* Type=Float64, ColorInterp=Undefined
Description = 0[-] MSL (Mean sea level)
Metadata:
GRIB_UNIT=[Pa]
GRIB_COMMENT=Pressure reduced to MSL [Pa]
GRIB_ELEMENT=PRMSL
GRIB_SHORT_NAME=0-MSL
GRIB_REF_TIME= 1242453600 sec UTC
GRIB_VALID_TIME= 1242453600 sec UTC
GRIB_FORECAST_SECONDS=0 sec
....
As u can see the size according to the its header is 161x98, but all
the bands are related as 161x1 block. Why does it happen? Another
thing I noticed is that the dif between upper and lower latitude in
the corner coordinates is very small (-61.246 to -61.426).
The issue is that, when mapserver renders this layer it only draws a
straight line below South America, exactly where the whole image
should start, as my CTL below shows.
dset ^T126L28.grb
title pac/sa/atlan sector: troposphere file
undef 1e+20
dtype grib
index ^T126L28.gmp
xdef 161 linear -150.000015 0.937500
ydef 98 levels
-61.246 -60.311
-59.376 -58.441 -57.506 -56.571 -55.636 -54.701 -53.766 -52.831
-51.896 -50.961
-50.026 -49.091 -48.156 -47.221 -46.286 -45.350 -44.415 -43.480
-42.545 -41.610
-40.675 -39.740 -38.805 -37.870 -36.935 -36.000 -35.065 -34.130
-33.195 -32.260
-31.325 -30.389 -29.454 -28.519 -27.584 -26.649 -25.714 -24.779
-23.844 -22.909
-21.974 -21.039 -20.104 -19.169 -18.234 -17.299 -16.364 -15.429
-14.493 -13.558
-12.623 -11.688 -10.753 -9.818 -8.883 -7.948 -7.013 -6.078
-5.143 -4.208
-3.273 -2.338 -1.403 -0.468 0.468 1.403 2.338 3.273
4.208 5.143
6.078 7.013 7.948 8.883 9.818 10.753 11.688 12.623
13.558 14.493
15.429 16.364 17.299 18.234 19.169 20.104 21.039 21.974
22.909 23.844
24.779 25.714 26.649 27.584 28.519 29.454
zdef 7 levels
1000 925 850 700 500 300 200 ===> set Z 1 ou 2 ou 3 ... ou 7 (GRADS)
tdef 1 linear 6Z16may2009 6hr
vars 15
psnm 0 2,102, 0, 0 SEA LEVEL PRESSURE [hPa]
tsfc 0 187, 1, 0, 0 SURFACE TEMPERATURE [K]
prec 0 61, 1, 0, 0 TOTAL PRECIPITATION [Kg/m2/day]
cbnv 0 71, 3, 0, 0 CLOUD COVER [0-1]
role 0 114, 8, 0, 0 OUTGOING LONG WAVE AT TOP [W/m2]
mask 7 137,100 MASK [-/+]
uvel 7 33,100 ZONAL WIND (U) [m/s]
vvel 7 34,100 MERIDIONAL WIND (V) [m/s]
omeg 7 39,100 OMEGA [Pa/s]
fcor 7 35,100 STREAM FUNCTION [m2/s]
potv 7 36,100 VELOCITY POTENTIAL [m2/s]
zgeo 7 7,100 GEOPOTENTIAL HEIGHT [gpm]
temp 7 11,100 ABSOLUTE TEMPERATURE [K]
umrl 7 52,100 RELATIVE HUMIDITY [no Dim]
umes 7 51,100 SPECIFIC HUMIDITY [kg/kg]
endvars
Can someone help me to find out what is happening?
Tks a lot
Roberto Garcia
Frank Warmerdam wrote:
Roberto Garcia,MSc wrote:
Hi, tks for the answers.
According to my gdainfo output file attached, can anyone tell me
what element could be a CLASSITEM?
Roberto,
In MapServer you always classify rasters based on the item [pixel] but
you do not need to explicitly state a classitem.
This is a relatively simple example of raster classification.
LAYER
NAME grid1
TYPE raster
STATUS default
DATA data/float.tif
CLASS
NAME "red"
EXPRESSION ([pixel] < -3)
COLOR 255 0 0
END
CLASS
NAME "green"
EXPRESSION ([pixel] >= -3 and [pixel] < 3)
COLOR 0 255 0
END
CLASS
NAME "blue"
EXPRESSION ([pixel] >= 3)
COLOR 0 0 255
END
END
I can see my grib using Grads but what tool do I use to translate
individual bands into GeoTIFF?
You can use gdal_translate to extract particular bands from a grib file
as a geotiff (or all the bands). For instance, the following would
extract band 3 (total precipitation):
gdal_translate -b 3 T126L28.grb total_precip.tif
Converting the data on-the-fly to an image is the right way to work?
Having MapServer access the grib file on the fly rather than depending
on pre-translated extracts will reduce data duplication and may help
avoid confusion about what is up to date. However, it is possible that
there will be a performance penalty for extracting directly from GRIB.
If so, it may not be significant enough to matter to you.
What are the problems with Apache if I do not do so?
I don't see how either approach relates to Apache. It is a
data management and possibly performance issue with MapServer.
Best regards,
------------------------------------------------------------------------
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