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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
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Hi Garrett- "Campbell, Garrett" wrote: > > I am attempting to use the mcidas meteosat navigation module > > The documentation is obscure. The best source for documentation is the McIDAS programmer's reference which documents the MSAT nav module. There is a link from the javadocs for MSATnav. > 1. Sometimes Mcidas lists longitude positive to the west. The convention in VisAD is positive east longitude which is opposite of McIDAS and VisAD. The *nav routines are java conversions of the McIDAS FORTRAN nav modules. Since the McIDAS transformations use positive west longitude, all incoming longitudes are multiplied by -1 before the transforms are done. > 2. line and elemement numbers are interchangable in some sence since the > Meteosat 7 > satellite is at 0 longitude. I don't think this is true. The line/element numbers refer to the file (AREA) coordinates. > 3. Line numbers could count from south to north or north to south. > Similarly element > numbers could count either increasing to the west (as the > satellite scans) or > increasing to the east (as a picture would show). In MSATnav, area ele/lin (0,0) is the first pixel in the (upperleft) corner of the image which I believe is the McIDAS convention. AREACoordinateSystem has 0,0 in the lower left and sets the flipped line coordinates flag in the nav module. > Has anyone used edu.wisc.ssec.mcidas.MSATnav? Yes, through AREACoordinateSystem. > What convention do you use for latitude and longitude/ line and element > in the routines calls to toLatLon and toLinEle. the default transforms are (element, line) <-> (Latitude, Longitude). Longitude is in degrees East. line and element are in file (AREA) coordinates not image coordinates. You can transform from file to image coordinates using the imageCoordToAreaCoord and areaCoordToImageCoord methods. I did the conversion from McIDAS FORTRAN to VisAD Java, so if you have a specific question, let me know. The code in the toLinEle and toLatLon methods is as well documented as the corresponding FORTRAN code (which is pretty much non-existant). Don ************************************************************* Don Murray UCAR Unidata Program dmurray@xxxxxxxxxxxxxxxx P.O. Box 3000 (303) 497-8628 Boulder, CO 80307 http://www.unidata.ucar.edu/staff/donm *************************************************************
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