Re: [netcdf-java] BUG: ucar.unidata.geoloc.LatLonPointImpl.betweenLon()

• To: netcdf-java@xxxxxxxxxxxxxxxx
• Subject: Re: [netcdf-java] BUG: ucar.unidata.geoloc.LatLonPointImpl.betweenLon()
• From: John Caron <caron@xxxxxxxxxxxxxxxx>
• Date: Wed, 14 Jul 2010 17:38:57 -0600

On 7/14/2010 8:02 AM, Christian D Ward-Garrison wrote:

So, I realized what the problem with LatLonPointImpl.betweenLon() (a problem that my proposed replacement shares): there's not enough information to determine which way (east or west) the longitude range extends. For example, how should

LatLonPointImpl.betweenLon(10, 20, 0);

be interpreted? Does that lon range extend from 20 west to 0 (20 degrees) or from 20 east to 0 (340 degrees)?

As a result, I've eschewed betweenLon altogether and started using LatLonRect instead:

new LatLonRect(new LatLonPointImpl(0, 20), 0, 340).contains(0, 10); // false new LatLonRect(new LatLonPointImpl(0, 20), 0, -20).contains(0, 10); // true

I think that betweenLon() should be made deprecated, since it'll give unexpected results for arguments such as:

LatLonPointImpl.betweenLon(45, 0, 360);

which is a Bad Thing, given how common [0, 360] is as a longitude range.

Regards,
Christian Ward-Garrison


-----netcdf-java-bounces@xxxxxxxxxxxxxxxx wrote: -----

    To: netcdf-java@xxxxxxxxxxxxxxxx
    From: Christian D Ward-Garrison <cwardgar@xxxxxxxx>
    Sent by: netcdf-java-bounces@xxxxxxxxxxxxxxxx
    Date: 07/13/2010 05:46AM
    Subject: [netcdf-java] BUG:
    ucar.unidata.geoloc.LatLonPointImpl.betweenLon()


      LatLonPointImpl.betweenLon(68, 52, 340)  // Returns false but
      should be true.


      The method fails because it normalizes lonEnd to -20, which is
      less than 68. I propose this fix:

      static public boolean betweenLon(double lon, double lonBeg,
      double lonEnd) {
          double lonNormal = lonNormal(lon, (lonBeg + lonEnd) / 2);

          // Don't assume that lonBeg <= lonEnd.
          return Math.min(lonBeg, lonEnd) <= lonNormal && lonNormal <=
      Math.max(lonBeg, lonEnd);
      }


      Regards,
      Christian Ward-Garrison

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• References:
  • [netcdf-java] BUG: ucar.unidata.geoloc.LatLonPointImpl.betweenLon()
    • From: Christian D Ward-Garrison
  • Re: [netcdf-java] BUG: ucar.unidata.geoloc.LatLonPointImpl.betweenLon()
    • From: Christian D Ward-Garrison