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Message: Seeking expert advice on ruc236

Posted by Mike Ross on 20 Feb 02, 8:01 MT

I hoping for some expert help in understanding a problem I am tying to solve. The problem concerns the acquiring of accurate weather data based on a aircrafts position expressed as Latitude/Longitude. At the center of the problem is the projection of a ruc236 40km Lambert Conformal grid to a nominal 25nm Conformal Spherical grid. What I am trying to understand is; If I just use the Lambert grid and use a algorithm based on W3FB11 by Stackpole to convert aircraft position lat/lon to (I,J) an get the weather values from that position will I be getting the correct data for that position? Horizontal only, vertical is another matter.
I am comparing this to the projection on to the Conformal Spherical grid. This method, from the User Request Evaluation Tool (URET) used in NAS first builds a new grid usually based on a ARTCC. The direct translation of Lambert to Spherical results in a non-uniform mesh grid. This non-uniform mesh grid is then converted into a uniform mesh grid of 25nm increments. It then takes the new coordinates at each grid point looks them up in the Lambert grid, gets the weather and does a bilinear interpolation from the surrounding 4 points to fill in the new grid point.
I believe I have explained this to the best of my understanding. I am trying to use ruc236 data to provide a target generation system with weather data that will be the as good as that used by URET. I just don't understand what the projection from Lambert Conformal to Conformal Spherical is gaining them with respect to accuracy of the weather.


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