Exactly so. Inertial Navigation relies on nothing other than the deflection of masses under a gravitational field; no VORs, no radio, no nothing.
For example, a/c takes off and crosswind hits from the right at 30kt. A/c accelerates left, to 30kt, and keeps going left. INS senses the acceleration. If it senses no other change in that direction, it will incorporate this drift of 30kt left into its calculated position.