Here is my current belief as to what is happening. The issues appears to be that you are asking for this dataset: http://data.nodc.noaa.gov/thredds/dodsC/ndbc/cmanwx/2011/01/NDBC_WPOW1_201101_D1_v00.nc to be returned as using the opendap format. The conversion to opendap currently does not support groups, so all groups are flattened into a single, top-level, group. This flattening attempts to put two variables with the same name but from different groups into the single flattened group; hence the error. You can see this by putting the following into your web browser. http://data.nodc.noaa.gov/thredds/dodsC/ndbc/cmanwx/2011/01/NDBC_WPOW1_201101_D1_v00.nc.dds You will see that the variable "wind_speed" occurs twice in that DDS. To correct the problem, you need to access the data using some other protocol besides opendap. Let me know if I am missing something here; if so, I will continue to look at the problem. =Dennis Heimbigner Unidata Ticket Details =================== Ticket ID: SBZ-133456 Department: Support netCDF Java Priority: Critical Status: Closed