The specific identifiable altitude still requires an arbitrary selection of lift coefficient and vehicle mass in order to calculate. The calculation is vehicle

The specific identifiable altitude still requires an arbitrary selection of lift coefficient and vehicle mass in order to calculate. The calculation is vehicle dependent, not general. The values used in the original definition of the general case were set to be "typical", which yielded 91km. Because of the arbitrariness of this definition, it was defined to be 100km as that was "more memorable"