grib/src/main/java/ucar/nc2/grib/grib1/Grib1SectionGridDefinition.java
public final boolean isThin() {
    if (rawData == null) return false;
    int octet5 = getOctet(5);
    int nv = getOctet(4);
    return (octet5 != 255) && (nv == 0 || nv == 255);
  }
public final boolean isThin() {
    if (rawData == null) return false;
    int octet5 = getOctet(5);
    int nv = getOctet(4);
    return (octet5 != 255) && (nv == 0 || nv == 255);
  }
is a "thin" grid

@return if a thin grid