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>From: Xinli Li <address@hidden> >Organization: University of Hawaii >Keywords: 200002252127.OAA12741 McIDAS-X solar zenith Xinli, >I have installed the McIDAS-X sucessfully. Thank you for your help! You are welcome. >Now I am using it to display the real satellite images. I have a >question about McIdas-X. > >Is lt possible to calculate the azimuth angles from each pixel of the >real image to satellite by using McIdas-X, and how? This is not something that is readily available in McIDAS, but other sites have done it. I sent off an email to the one site that is doing this on a regular basis asking them to share the code they developed with you and the rest of the McIDAS community. >This is very important to us, I didn't find any things about this >function on the McIdas-X documents. I will get back to you with the code/technique as soon as I hear from the site I contacted. >Best regard, >Xinli Li Tom >From address@hidden Thu Mar 2 14:58:34 2000 >Date: Thu, 2 Mar 2000 16:58:26 -0500 (EST) >From: "Jennie L. Moody" <address@hidden> >To: address@hidden >Subject: Re: 20000225: solar zenith angles for satellite imagery Tom, We did this a couple different ways, orginally we had a grid of zenith angles calculated once offline (they don't change unless somebody moves a satellite), but under version 7.6 of McIDAS that stopped working, however, there were some new math functions (that return the lat and log on a grid point) that made it pretty easy to calculate the zenith angles dynamically. So now a new grid of zenith angles is made each time the product gets made. We use a set of equations from Kidder and VonderHaar's book Satellite Meteorology. Its section 2.5.2 where they define the zenith angle based on a number of vectors to a point a earth (in this case, tracking atenna's, in our case, grid cell locations). Anyway, Tony worked on coding this and so I have sent him a copy of your message. He will be in touch with you about making the code available, either as a contrib, or whatever other way it might be helpful. Its pretty simple code to get the zenith angle, now, how people use the zenith angle to make "corrections" to radiances is another whole issue. In our case, we were able to rely on the results of some research by other investigators (Soden and Bretherton) who had used a radiative transfer model.