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Re: [idvusers] aircraft track data

Dear Larry,
Many thanks for the script. It worked like a charm. IDV reads in the file now without any problem. Thanks to all who helped. 

Best wishes,
Sebastian



On 04/14/2011 06:09 PM, Larry D. Oolman wrote:

There may be multiple ways to make the file work but I am most
familiar with the track files produced from the US
National Science Foundation aircraft.

1) There needs to be three global attributes
        :conventions = "NCAR-RAF/nimbus" ;    // Note this is a change from 
"CF-1.0 that is in the file
        :Version = "1.3" ;                    // This is optional, it defaults 
to 1.3
        :coordinates = "LON_GPS LAT_GPS GPS_ALT Time" ;       // Tells IDV what 
position variables to use.
2) For IDV to work the second dimension, sps01, must be eliminated.
3) The Time dimension and the Time variable must be named the same.

Attached is a script that uses NCO to correct the file.  In the file you
sent me in a separate email, there are some zeros at the beginning of
the data for the GPS positions.  I took the liberty to change the
_FillValue attribute from -9999 to 0.

Kristian Sebastián wrote:

Hi Sebastian,

Attached, you have a cdl example of NetCDF that can be ploted with the IDV.
The NetCDF file must have one time dimension (only one dimension is allowed)
and the coordinate variables time, longitude, altitude and latitude (CF
Conventions Coordinate
Types<http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.5/cf-conventions.html#coordinate-types>
).

Your NetCDF have two dimensions, you can delete sps01 and rename data_point
to time dimension. You must also add the coordinate variables, and all the
variables (coordinate and data) must have the time dimension.

Best wishes,

2011/4/11 Yuan Ho<yuanho@xxxxxxxxxxxxxxxx>


On 4/11/2011 10:44 AM, Don Murray wrote:


Yup. However, the netCDF-Java library doesn't recognize this and reduce
the dimension as I recall. I'm not sure there's any NcML that you could
use to do that for you either.

Don


Hi Sebastian
If you can upload a sample data, I will check to see if we need to do any
modification to display this dataset in the IDV.

http://motherlode.ucar.edu/repository/alias/idvupload

Yuan



On 4/11/11 10:42 AM, Larry D. Oolman wrote:


Don Murray wrote:


I'm not sure the IDV handles the 2D dimensions. I would suggest
sending a note to support-idv@xxxxxxxxxxxxxxxx.

Don


If the file is RAF/Nimbus, the second dimension is not required for
one sample per second data.



On 4/10/11 12:39 PM, Sebastian Engelstaedter wrote:


Hi all,

I am new to IDV but it looks like a powerful tool. I want to plot
aircraft track data which come in netCDF format. However, IDV is unable
to read in the current netcdf file I have. Can someone point me to the
correct format. At the moment the netcdf file looks something like
this:


dimensions:
data_point = UNLIMITED ; // (28980 currently)
sps01 = 1 ;
variables:
int Time(data_point) ;
Time:long_name = "time of measurement" ;
Time:units = "seconds since 2011-04-04 00:00:00 +0000" ;
Time:_FillValue = -1 ;
Time:standard_name = "time" ;
float IAS_RVSM(data_point, sps01) ;
IAS_RVSM:long_name = "Indicated air speed from the aircraft RVSM (air
data) system. " ;
IAS_RVSM:units = "m s-1 " ;
IAS_RVSM:_FillValue = -9999.f ;
IAS_RVSM:Frequency = 1s ;
IAS_RVSM:Number = 516s ;
byte IAS_RVSM_FLAG(data_point, sps01) ;
IAS_RVSM_FLAG:long_name = "Flag for Indicated air speed from the
aircraft RVSM (air data) system. " ;
IAS_RVSM_FLAG:units = 1s ;
IAS_RVSM_FLAG:_FillValue = -1b ;
IAS_RVSM_FLAG:Frequency = 1s ;
float TAS_RVSM(data_point, sps01) ;
TAS_RVSM:long_name = "True air speed from the aircraft RVSM (air data)
system and deiced temperature. " ;
TAS_RVSM:units = "m s-1 " ;
TAS_RVSM:_FillValue = -9999.f ;
TAS_RVSM:Frequency = 1s ;
TAS_RVSM:Number = 517s ;
TAS_RVSM:standard_name = "platform_speed_wrt_air" ;
byte TAS_RVSM_FLAG(data_point, sps01) ;
TAS_RVSM_FLAG:long_name = "Flag for True air speed from the aircraft
RVSM (air data) system and deiced temperature. " ;
TAS_RVSM_FLAG:units = 1s ;
TAS_RVSM_FLAG:_FillValue = -1b ;
TAS_RVSM_FLAG:Frequency = 1s ;
float TAT_DI_R(data_point, sps01) ;
TAT_DI_R:long_name = "True air temperature from the Rosemount deiced
temperature sensor. " ;
TAT_DI_R:units = "degK " ;
TAT_DI_R:_FillValue = -9999.f ;
TAT_DI_R:Frequency = 1s ;
TAT_DI_R:Number = 520s ;
TAT_DI_R:standard_name = "air_temperature" ;
....




Any help is much appreciated.

Best wishes,
Sebastian



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--
__________________________________________

Sebastian Engelstaedter
School of Geography and the Environment
Oxford University Centre for the Environment
University of Oxford
South Parks Road, Oxford, OX1 3QY, UK
phone +44 1865 275867
fax +44 1865 275885
__________________________________________
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