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On Tue, 2006-03-14 at 09:21, address@hidden wrote: > I need to be able to compute the gradient between two points for which I > will only know the lat/lon values. I'm looking for the easiest way to do > this. Is there a way to spit out the value for a parameter by providing a > single lat/lon? Matt, Yes, you could use the GDPOINT program to output a value at a specific GPOINT. You can also use the ddx(), ddy(), and/or grad() grid diagnostics at an intervening lat/lon. > Or alternatively, is there a simple way of obtaining the > actual gridpoints for a location if I only know the latitude/longitude > coordinates so that I can easily reference the grid points in a Fortran > program? The GEMPAK library provides a function GR_PLOC that accepts the character string for GPOINT (which may be grid point locations, lat/lon, station id etc), and provides back the projected grid point location as well as lat/lon values (you could add a write(*,*) statement tothe $NAWIPS/comet/gdpoint/gdpoint.f routine to output the rgy and rgy location following the GR_PLOC call if you wanted to use that program as a starting point). Steve Chiswell Unidata User Support > > Matt Borkowski > Graduate Student > North Carolina State University > Department of Marine, Earth, and Atmospheric Science >