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>From: David Harper <address@hidden> >Organization: NCAR/RAP >Keywords: 200003012325.QAA04248 McIDAS-X GINI netCDF Dave, re: Lat,Lon comparisons at UL and LR corners are within 2 parts per 1000 >Actually I made that same comparison. I think the problem is in the image, >not the coordinates. When we look at it in Zebra, White Sands and the river >are displaced relative to the coordinates. I looked up the location of White Sands in an atlas and get a location of 32:50N, 106:20W. Given that the white sands themselves cover quite a bit of ground, there is no telling if the numbers I get back from the center of the white sand feature represent the location listed in the atlas. My listings show that the east-west size of the sands is only about 0.39 degrees across (at 32.9N). A shift of 0.5 degrees would, therefore, be quite noticable. Also, when I load the original GINI image or its AREA copy in McIDAS and put a high resolution map on it, I get very good agreement with the location of the Rio Grande and the Texas/Mexico border. To see how the image looks in McIDAS (with brightnesses exaggerated so that the river and the sands can be seen easily), please check out: http://www.unidata.ucar.edu/staff/tom/whitesands.gif Can you provide me with browser loadable rendition of what you are seeing in Zebra? >Have you compared the actual data values at those points? That might be >more telling. The comparison for Lat,Lon and data values is: point netCDF brightness McIDAS AREA brightness ------------+---------------------+----------------------------- 1,1 75 74 800,800 83 82 point netCDF Lat,Lon [deg] McIDAS AREA Lat,Lon [deg] ------------+---------------------+----------------------------- 1,1 36.32418N 110.7891W 36.32222N 110.79055W 800,800 29.71597N 101.4901W 29.71333N 101.49055W The discrepency in the brightness values could be the 1 pixel offset that I mentioned in my first note. Tom
