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Hi Brian- > Full Name: Brian Billings > Email Address: address@hidden > Organization: Naval Research Laboratory > Package Version: 2.7u2 > Operating System: Windows Vista > Hardware: > Description of problem: Have any issues been reported on using the simple > difference formula where one of the fields is an objective analysis of point > data? I have been trying to use this option on a 2D vis5d file and a text > data listing. The times are the same and the units are the same, but the > results are obviously incorrect. The users guide says that the calculation is > automatically performed only on the area in which the grids overlap, but this > is not being done in my output. Is the issue with using an objective analysis > or some other possibility? Thanks. If you are subtracting temperatures, the values will end up in K so if you convert to Celsius you'll be off by a factor of 273. The IDV does not distinguish between delta degrees K and regular K so a conversion between units will treat them as absolute. If that's not what you are seeing, could you upload the vis5d file and the text data to: http://motherlode.ucar.edu/repository/alias/idvupload so I can take a look. Let me know what field you are trying this with. Don Murray > > Ticket Details =================== Ticket ID: WWB-790357 Department: Support IDV Priority: Normal Status: Open