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> Julien and/or Yuan, > > I'm running IDV v2.9u2 on various Macs running Mac OS X v10.6.5. > > I ran into a problem a year ago with an earlier iteration of the IDV (which I > didn't report) that is still present in v2.9u2. The other day I discovered an > interesting twist on the problem that might offer some insight to help solve > it. > > I have students create a display, the data source for which is NAM model > output in a file residing on one of our local computers (virga.sfsu.edu). > Virga is a Web server, and students load the data source from virga using its > URL. > > The display itself comprises (a) mean sea-level pressure (a color-filled > contour plot); (b) surface wind vectors; and (c) 500-1000 mb thickness (a > contour plot). Both the wind vectors and 500-1000 mb thickness are derived > quantities. The thickness is calculated from the 500 mb and 1000 mb > geopotential heights. > > Students create the display successfully, then save it as a bundle. > > When the IDV opens the bundle, loads the data source, and tries to create the > display, it creates the MSLP and wind vector fields successfully. However, it > can't load the geopotential height fields needed to derive the 500-1000 mb > thickness field and plot it, and for that plot it generates an error message. > > However, virga is not only a Web server but also a RAMADDA server. When I > edit a typical student bundle and change the data source URL to a RAMADDA > reference to the same file on the same machine, the bundle works fine--no > problem with any of the three fields, including the 500-1000 mb thickness. > > So the question is, what is it about accessing a data source via the Web > server that causes a problem for some fields (or at least the thickness field > derived from geopotential heights in a NAM forecast output file) but not > others, but that isn't a problem when the same file is accessed on the same > computer using RAMADDA? Hi Dave, It is very different accessing a data file via the web server or the RAMADDA server, the RAMADDA is operating and/or sending the data via OPeNDAP. But, in the web server, it doesn't have any better way to operate process the data, it will treat the data the same as a html file, in many situation when there is a compression involved, it will be more trouble. Anyway, it is not recommended to use web server for large grid data file. Yuan , > > I've attached a copy of each bundle, which are identical except for the three > (identical) data source references in the bundle. Let me know if you need > anything else, such as the error message produced when the IDV tries to > download the geopotential height fields needed to computer thickness. > > No big rush on this. I hope you're enjoying the holidays! > > -- Dave > > ************************************************************ > * Dr. Dave Dempsey | ^ ___ \|/ * > * Dept. of Geosciences | ) ^ /||_||\ --0-- * > * San Francisco State University | ) ) / ||_|| \ /|\ * > * 1600 Holloway Ave. | ) ) / ||_|| \ * > * San Francisco, CA 94132 | ) ) / ||_|| \ ^ * > * | ) ) ) > ||_|| \ * > * Phone: (415) 338-7716 | ) ) )~||~||~~~~ \~~* > * FAX: (415) 338-7705 | ) ) ) ) ~ ~ ~ ~ ~ ~* > * Email: address@hidden | ) ) ) ) ) ~ ~ ~ ~ * > ************************************************************ > > > > > Ticket Details =================== Ticket ID: SRG-800720 Department: Support IDV Priority: Normal Status: Closed