The IDL DataPoint has an article about native OPeNDAP support in IDL 8.2. This allows the use of IDL’s netCDF API to access remote data served via the DAP protocol (this is new for the Mac on 8.2, already present in Linux, and still not working on Windows as I mentioned in my review of IDL 8.2).
Mark shows an example of how to access some AIRS data at The HDF Group’s OPeNDAP-enabled server. I have some netCDF bindings that will work for remote data as long as the underlying library is capable; the seven NCDF_OPEN, NCDF_VARID, and NCDF_VARGET commands in the example can be replaced with:
IDL> topo = tx_nc_getdata(url, 'TopographyU274')
IDL> latitude = tx_nc_getdata(url, 'LatitudeU271')
IDL> longitude = tx_nc_getdata(url, 'LongitudeU272')
Contact me if you are interested.
April 25th, 2013 at 12:54 pm
Is OPENDAP IDL supported in Window IDL8.2 yet?? Thanks!
April 25th, 2013 at 1:34 pm
No, Exelis VIS is waiting for an update from Unidata. It doesn’t look like it will be in IDL 8.2.3 which is coming soon.
July 18th, 2013 at 3:40 pm
Greetings!
I have a THREDDS Data Server, which, for gathering user metrics, we have password-protected data.
I have used the AIRS example you speak of successfully in our version (8.2.1) if IDL. However, I do not seem to be able to access my own TDS with a supplied user/pass syntax as
http://USERNAME:PASSWORD@server.domain/thredds/dodsC…
I have successfully employed this syntax with other OPeNDAP clients (except Matlab: see
http://www.mathworks.com/help/matlab/import_export/importing-network-common-data-form-netcdf-files-and-opendap-data.html#btbg07p-1
)
and was wondering if IDL has a similar inability to handle password protected data. I don’t see any mention of OPeNDAP at all in the Exelis forums and hoped that you might be able to shed some light on this.
Cheers!
July 18th, 2013 at 4:30 pm
I haven’t had to access password protected data via OPeNDAP and I don’t have a site to test it on right now. But, I think you should be able to use
NCDF_OPENwith a URL that contains a username and password. I would be curious if can give this a try!July 19th, 2013 at 11:05 am
Thanks for the reply!
I can successfully run ncdump (netCDF v4.2) connecting to my protected TDS OPeNDAP server, which makes me think that there might be a problem – perhaps netCDF version?
I ran into a similar issue with the GrADS http://www.iges.org/grads/ client. Their developers are looking into it. They are running netCDF v4.1.2
If you have time and want to test against our TDS, you can register for a free account at:
https://rda.ucar.edu/index.html?hash=data_user&action=register
Then go to TDS at:
http://castle.ucar.edu/thredds/
and enter credentials. (Note: dealing with a bug where first login of the day may require a couple – less than 5 – attempts. Hope to have that figured out soon.)
I understand if these are too many hoops to jump through. I will likely register for an account on the IDL forums and post there as well.
Thanks!
July 19th, 2013 at 2:44 pm
I registered and can access data via the web page (experienced the same login problem you describe, glad you warned me). What URL were you trying to access (and worked via
ncdump)?July 19th, 2013 at 2:50 pm
Thank you so much for taking the time to register and try this! My apologies for leaving out the URL.
Try the following:
ncdump -h http://USERNAME:PASSWORD@castle.ucar.edu/thredds/dodsC/FNLCollection/best
Note that since the username is your email address, you will need to replace the ‘@’ with ‘%40’, as in:
myemail@mydomain.com should be myemail%40mydomain.com
You should get about 1500 lines of the metadata header. I just verified that it still works:
manross@yslogin6[home/manross] % ncdump -h http://MYEMAIL:MYPASSWORD@castle.ucar.edu/thredds/dodsC/FNLCollection/best
netcdf best {
dimensions:
altitude_above_msl = 3 ;
height_above_ground = 1 ;
height_above_ground1 = 1 ;
isobaric = 26 ;
isobaric1 = 21 ;
isobaric2 = 6 ;
isobaric3 = 1 ;
isobaric4 = 2 ;
lat = 181 ;
layer_between_two_depths_below_surface_layer = 4 ;
…
July 19th, 2013 at 3:24 pm
OK, I can get it to work from the OS command line with
ncdumpnow. IDL’s netCDF routines don’t seem to work, though:I will look at this a bit more.
July 19th, 2013 at 3:29 pm
Yep – that’s the error I am getting as well with ncdf_open(). Thank you very much for taking the time to examine this.
July 19th, 2013 at 3:30 pm
Ah! It appears it is the version of netCDF used by IDL. IDL 8.2.3 (most recent version) uses netCDF 4.1.1. If I use netCDF 4.1.1’s
ncdump, I get the same error:July 19th, 2013 at 3:33 pm
Looks like we need IDL to update it’s netCDF library.
July 19th, 2013 at 3:46 pm
Agreed. To whom should this be addressed? (I assume you have much, much more pull in this area than I would).
Thanks again for verifying this!
July 19th, 2013 at 3:54 pm
I’m asking around, but you should send an email to Exelis VIS support (support at exelisvis dot com).
July 19th, 2013 at 3:55 pm
Will do – thanks!
July 19th, 2013 at 3:56 pm
Will do – thanks!!
July 22nd, 2013 at 11:51 am
I have word that netCDF 4.3.0 should be in IDL 8.3.