On 4/9/2010 9:34 AM, Kevin O'Brien wrote:
Hi John -
John Caron wrote:
4/7/2010
3:05 PM, Kevin O'Brien wrote:
Hi John -
I've been working lately with Rich Signell to add a bunch of IOOS
Forecast Model Run Collections to the UAF THREDDS server at
http://ferret.pmel.noaa.gov/geoide/geoIDECleanCatalog.html
One thing I've noticed about all of the FMRC that I've run across is
that the "best time series" data seems to use NaN as the missing
value. This seems fine, except that the missing value attribute is not
defined for the particular variables. I know this causes a bit of a
problem when Ferret looks at the data, and I can imagine it might have
ramifications for other clients as well. There are several ways that I
can work around this, and one way I've done it is to wrap the FMRC with
some NcML defining the _FillValue attribute as NaN for the
variables. This works, but also means a loss of performance because
now the data has to take two hops, from our TDS and the TDS it
originally is served from.
Anyway, should it be that by default, the missing_value or _FillValue
attribute is defined as NaN in the "best time series" data?
Thanks
Kevin
I think it will use the value in missing_value or _FillValue if
defined. If not defined, NaN is apparently the default choice. I
suppose the right thing to do is to add that attribute if not defined,
for consistency. do you agree?
Hi John -
Thanks for getting back to me.
Actually, in looking a little deeper into the issue after I emailed
you, I think there might be something else going on that I don't
understand.
If you look at the best time series at:
http://geoport.whoi.edu:8081/thredds/dodsC/coawst/fmrc/coawst_2_best.ncd.html
The variable ZETA has these attributes (as seen through the HTML
interface):
long_name: "free-surface"
units: "meter"
time: "ocean_time"
field: "free-surface, scalar, series"
_FillValue: 0.0
coordinates: "lon_rho lat_rho ocean_time "
which is consistent with the individual forecast files.
However, when I actually look at the data:
http://geoport.whoi.edu:8081/thredds/dodsC/coawst/fmrc/coawst_2_best.ncd.ascii?zeta[0:1:10][0:1:10][0:1:10]
I see the below:
Dataset {
Float32 zeta[ocean_time = 11][eta_rho = 11][xi_rho = 11];
} coawst/fmrc/coawst_2_best.ncd;
---------------------------------------------
zeta[11][11][11]
[0][0], NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN
[0][1], NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN
[0][2], NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN
[0][3], NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN
[0][4], NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN
[0][5], NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN
[0][6], NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN
[0][7], NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN
[0][8], NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN
[0][9], NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN
[0][10], NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN
[1][0], NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN
[1][1], NaN, -4100.3965, -4096.8623, -4090.378, -4082.1177, -4072.744, -4062.7856, -4052.7595, -4043.087, -4034.1382, -4026.2202
[1][2], NaN, -4112.4053, -4108.7847, -4102.329, -4093.9312, -4084.07, -4073.1624, -4061.7964, -4050.805, -4041.122, -4033.1853
[1][3], NaN, -4129.4663, -4125.637, -4119.091, -4110.316, -4099.464, -4086.7424, -4072.8909, -4059.5364, -4048.5781, -4040.5977
[1][4], NaN, -4147.614, -4143.8057, -4137.275, -4128.0645, -4115.893, -4100.7466, -4083.5476, -4066.868, -4053.7632, -4044.9514
[1][5], NaN, -4165.1304, -4161.61, -4155.5195, -4146.2856, -4133.0703, -4115.5186, -4094.48
So, it appears that there are both missing/_FillValues of 0, as well as
NaNs scattered through the dataset....Should the NaNs be the same as
the _FillValue in this case?
yes, probably. ill have a look at that.
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