Re: Set grid zone in latlon2utm?

On Sep 13, 2012, at 7:42 AM, Andrea N. Hahmann wrote:

> Hello In the NCL function "latlon2utm" is it possible to set the grid zone (I need "32U")?

Hi Andrea,

I had to look at the code to see what's allowed. From what I can tell, there's no recognition of "32":

In the code below "zone_long" comes from the first two characters of "grid_zone", and "zone_lat" comes from the 3rd character. Note that it prints an error if you give it "32":

  zone_long = (grid_zone[0] - '0') * 10 + (grid_zone[1] - '0');
  zone_lat = grid_zone[2];

  /* Take care of special cases */

  switch(zone_lat) {
  case 'A': case 'B': case 'Y': case 'Z':
    *lambda0 = 0;
    return(0);
    break;
  case 'V':
    switch (zone_long) {
    case 31:
      *lambda0 = 1.5 * M_PI / 180.0;
      return(0);
      break;
    case 32:
      *lambda0 = 7.5 * M_PI / 180.0;
      return(0);
      break;
    break;
    }
  case 'X':
    switch (zone_long) {
    case 31:
      *lambda0 = 4.5 * M_PI / 180.0;
      return(0);
      break;
    case 33:
      *lambda0 = 15 * M_PI / 180.0;
      return(0);
      break;
    case 35:
      *lambda0 = 27 * M_PI / 180.0;
      return(0);
      break;
    case 37:
      *lambda0 = 37.5 * M_PI / 180.0;
      return(0);
      break;
    case 32: case 34: case 36:
      NhlPError(NhlWARNING,NhlEUNKNOWN,"utm2latlon/latlon2utm: Zone %02d%c does not exist!\n",zone_long, zone_lat);
      return(-1);
      break;
    }

I don't recall at the moment where this code came from, or why cases 32, 34, and 36 produce an error. If you know the proper calculation, I can easily add it.

--Mary

> This is possible in the reverse function "utm2latlon". From the function documentation:
> xy = (/285039.989723,3776960.118351/)
>
> xy@grid_zone = "11S"
>
>
>
> latlon =
>
> utm2latlon(xy,0) ; 34.113, -119.331
>
>
> Thanks,
> Andrea
>
> ----
> Andrea N. Hahmann
> Senior Scientist
> DTU Wind Energy
>
> Technical University of Denmark
> Risø Campus
> Frederikborgvej 399, P.O. Box 49
> 4000 Roskilde, Denmark
>
> Direct +45 4677 5471
> Mobil: +45 2133 0550
> ahah@dtu.dk
> http://www.vindenergi.dtu.dk/
>
>
>
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Received on Mon Sep 17 09:44:37 2012