I propose a general class of spacetimes whose structure is governed by obse
rver-independent scales of both velocity (c) and length (Planck length), an
d I observe that these spacetimes can naturally host a modification of Fitz
Gerald-Lorentz contraction such that lengths which in their inertial rest f
rame are bigger than a "minimum length" are also bigger than the minimum le
ngth in all other inertial frames. With an analysis in leading order in the
minimum length, I show that this is the case in a specific illustrative ex
ample of postulates for relativity with velocity and length observer-indepe
ndent scales. (C) 2001 Elsevier Science B.V. All rights reserved.