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>From: Anthony James Wimmers <address@hidden> >Organization: UVa >Keywords: 199905071731.LAA07790 GRDDISP MERidional Tony, >Is it necessary to use the MERIDIONAL keyword on operations on MRF >(mercator) or ETA (lambert-conf) grids? The MERidional= keyword for GRDDISP only has an affect for the DERIVE=ABV, DSH, DST, DVG, or VOR fields. For any other derived other derived field, it has no effect. To answer your question, no it is not _necessary_ to add the MER= keyword for MRF or ETA grids, but it does help correct for the smaller and smaller distances between longitude lines as one approaches the pole. I think you will find that the effect of teh adjustment is small, however. Tom