code: public static double getValue( GridCoverage2D raster, double easting, double northing ) {
          double[] values = null;
          try {
              values = raster.evaluate(new Point2D.Double(easting, northing), (double[]) null);
          } catch (Exception e) {
              return doubleNovalue;
          }
          return values[0];
      }
docs: Simple method to get a value from a single band raster.
  
  <p>Note that this method does always return a value. If invalid, a novalue is returned.</p>
  
  @param raster
  @param easting
  @param northing
  @return