SEG-Y header field definition at the last byte location doesn't work
SEGYImport does not allow reading the last FourByte header word from the SEGY header. If the crossline in the last header word, you can define a JSON file as follows:
{
"InlineNumber" : [ 233, "FourByte"],
"CrosslineNumber" : [ 237, "FourByte"]
}
This gives an ‘illegal field’ definition error because the code checks that 237 + 4 is no more than 240 which is off-by-one.