Tom Whittaker wrote:
The "angles" are the azimuth angles that Don Murray mentioned. Since each time might have a different structure (as Don said, one starting at 170 degrees and the next at 176), you may have difficulties with the resampling.
Indeed - thanks the for clarification. I keep thinking angles in terms of up and not to the left or right. ;)
The "rule" for resampling when combining data is this: The coordinate system of the result will be the coordinate system of the first-named variable. These means that when summing up using that little code snippet, an attempt will be made to resample all the data to the coordinates of "g".
ok - so then let me know if this is possible: I assume we are agreed on what a "gate" is.... Set up two arrays of two dimensions each (az, ra). Range wants to be even km for REF, of course. Az can be any resolution. Even degrees (0-359) is convenient and is assumed below. The two arrays hold the data for averaging one elevation for >1 scan (so two dimensions are enough, but that is a detail). SumZ Holds the sum of Z (not dBZ) for all gates and portions of gates that fall in that azimuth and range. N Holds the number of gates that have contributed to SumZ. This is not usually an integer. Most Nexrad gates will have azimuths that are not even integers. (An azimuth such as 15.000 degrees is an edge case in the coding.) The procedure is to convert each range gate's dBZ value to Z and compute what two SumZ azimuths it overlaps. Then run along the ranges. Add z*p and z*(1-p) to the two elements of SumZ. Add p and (1-p) to the two elements of N. After all the desired scans have been summed in this way, divide SumZ by N to get average Z and convert to dBZ for displaying. Can that be done in IDV? -Ben