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 Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated.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.
Hi Tom- I changed the way u and v are defined in aliases.xml and how they are used in the derived.xml to create the automatic derived quantities. If I use the strategy that is used for the netCDF files for GRIB, it will break bundles because the parameter names will change. So now, you will see a Flow Vector and a True Flow Vector for all grids regardless of whether they are grid relative or true. In my experience, the global grids (lat/lon) are true and all the rest are grid relative. Let me know what you think. Will be in the next nightly build. Don > On Wed, Oct 21, 2009 at 8:50 AM, Unidata IDV Support > <address@hidden> wrote: > > Hi Tom- > > > > Sorry for the silence on other issues. I'll get back to you on them today. > > > > The problem is being able to identify whether the vectors are grid relative > > or true. In the netCDF files, there was a flag indicating this. In the > > grib messages, there hasn't been one. We are working with the netCDF group > > to get access to that info so we can distinguish the two. Right now, the > > distinction is made in the aliases as to whether the u and v components map > > to U and V or UREL and VREL. I'll check with the netCDF group on the > > status of this and get back to you. > > > > Don > > > >> When I get some model grids (in this case, the GSM 191km AK region), > >> the option in the "Derived" menu (in the Field Selector) is for flow > >> vectors from the grid. If I want "grid relative" (which corrects the > >> angle of the vectors for the direction it appears), then I have to use > >> a formula. > >> > >> Since the vast majority of (model) gridded data we get has u- and > >> v-comps in grid relative, I'm wondering why you might have chosen to > >> not put that option in the "Derived" section? > >> > >> I'm asking because I'm thinking about trying to get the McV to add > >> that to the "Derived" for McV....unless you tell me that my head is on > >> backwards (you know, that "wrong headedness factor" again.... ;-) > >> > >> Thanks for any info.... > >> > >> tom > >> > >> -- > >> Tom Whittaker > >> University of Wisconsin-Madison > >> Space Science & Engineering Center (SSEC) > >> Cooperative Institute for Meteorological Satellite Studies (CIMSS) > >> 1225 W. Dayton Street > >> Madison, WI 53706 USA > >> ph: +1 608 262 2759 > >> > >> > > > > > > Ticket Details > > =================== > > Ticket ID: MPQ-882676 > > Department: Support IDV > > Priority: Normal > > Status: Open > > > > > > > > -- > Tom Whittaker > University of Wisconsin-Madison > Space Science & Engineering Center (SSEC) > Cooperative Institute for Meteorological Satellite Studies (CIMSS) > 1225 W. Dayton Street > Madison, WI 53706 USA > ph: +1 608 262 2759 > > Ticket Details =================== Ticket ID: MPQ-882676 Department: Support IDV Priority: Normal Status: Open