Hi Rich, I was able to get this down to a minimal test case by using only the variable 'pn' and 'u': http://geoport-dev.whoi.edu/thredds/ncss/coawst_4/use/fmrc/coawst_4_use_best.ncd?var=pn&var=u&north=48.4639&west=-101.7498&east=-53.2530&south=11.8884&horizStride=1&time=2016-01-29T00%3A00%3A00Z&vertCoord=15&addLatLon=true&accept=netcdf What's happening here is that 'u' has a vertical coordinate equal to 's_rho' and 'pn' has a vertical coordinate equal to 'null'. So *technically* the error message is correct. Whether it makes sense to reject such a query is another matter, of course. It would be interesting to test this again on 5.0. All of the GeoGrid stuff got replaced with GridCoverage, so it may not be an issue any more. If nothing else, I wouldn't want to attempt to fix this on 4.6 when the code has changed so drastically in 5.0. The vertical level is coordinate-based, like everything else in NCSS. Just enter the value you want; don't worry about the index underneath. -Christian Ticket Details =================== Ticket ID: QLQ-406940 Department: Support THREDDS Priority: Normal Status: Closed