[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[IDV #CGA-206836]: Multiple trajectories in a single file

This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.

  • Subject: [IDV #CGA-206836]: Multiple trajectories in a single file
  • Date: Wed, 31 Aug 2022 14:51:54 -0600
> Thanks, Yuan.  I was hoping to avoid the "multidimensional array" approach 
> since, with staggered (in time) trajectories, there are a lot of missing 
> data.  I can give it a try, though.  One follow- up question: your time 
> dimension example has "days since 1970-01-01 00:00:00".  Can I use epoch time 
> instead (seconds since 1970-01-01 00:00:00)?
> 
> - Adam
> 
> 
Yes, I don't see any problem with it.

Yuan
> -----Original Message-----
> From: Unidata IDV Support <address@hidden>
> Sent: Monday, August 29, 2022 4:41 PM
> To: Adam Houston <address@hidden>
> Cc: address@hidden; Adam Houston <address@hidden>
> Subject: [IDV #CGA-206836]: Multiple trajectories in a single file
> 
> Non-NU Email
> 
> > Finally got back to this and created an example netcdf file (attached) that 
> > adheres to the CF "Contiguous ragged array representation of trajectories" 
> > convention 
> > (https://urldefense.com/v3/__https://cfconventions.org/Data/cf-conventions/cf-conventions-1.9/cf-conventions.html*_contiguous_ragged_array_representation_of_trajectories__;Iw!!PvXuogZ4sRB2p-tU!FQkxrNIl_WKyfKN5sF5xntqoy0u-5-uBZCE1LLA_FWLl29bDz5t1yHTePbLfF7psbaythVz43Y-0-WKHIZynupg6rhU6vg$
> >   ).  I tried opening this in version 6.1 using "netcdf/GEMPAK Point data 
> > files" and "point cloud data (netcdf)" but neither appears to work (no 
> > errors but nothing happens).
> >
> > - Adam
> >
> >
> 
> Hi Adam,
> 
> The coordinates of your netCDF file need to be like the following:
> 
> double time(trajectory, obs) ;
> time:standard_name = "time";
> time:long_name = "time" ;
> time:units = "days since 1970-01-01 00:00:00" ;
> float lon(trajectory, obs) ;
> lon:standard_name = "longitude";
> lon:long_name = "longitude" ;
> lon:units = "degrees_east" ;
> float lat(trajectory, obs) ;
> lat:standard_name = "latitude";
> lat:long_name = "latitude" ;
> lat:units = "degrees_north" ;
> 
> For a file with multiple trajectories, we use two dimensions: trajectory and 
> obs, to define all trajectories. Here is the document:
> 
> https://urldefense.com/v3/__https://cfconventions.org/cf-conventions/cf-conventions.html*_multidimensional_array_representation_of_trajectories__;Iw!!PvXuogZ4sRB2p-tU!FQkxrNIl_WKyfKN5sF5xntqoy0u-5-uBZCE1LLA_FWLl29bDz5t1yHTePbLfF7psbaythVz43Y-0-WKHIZynupgwSt-yAQ$
> 
> Yuan
> 
> Ticket Details
> ===================
> Ticket ID: CGA-206836
> Department: Support IDV
> Priority: Normal
> Status: Open
> ===================
> NOTE: All email exchanges with Unidata User Support are recorded in the 
> Unidata inquiry tracking system and then made publicly available through the 
> web.  If you do not want to have your interactions made available in this 
> way, you must let us know in each email you send to us.
> 
> 
> 


Ticket Details
===================
Ticket ID: CGA-206836
Department: Support IDV
Priority: Normal
Status: Open
===================
NOTE: All email exchanges with Unidata User Support are recorded in the Unidata 
inquiry tracking system and then made publicly available through the web.  If 
you do not want to have your interactions made available in this way, you must 
let us know in each email you send to us.