Abstract: The article undertakes analysis of some vital aspects of inertial navigation using MEMS. Although MEMS inertial sensors offer affordable, scaled units, and though their inherent measurement noise can be relatively easily mitigated, there are still parameters due to which they are not currently capable of meeting all requirements for accurate inertial navigation. The article presents a few aspects of MEMS gyro errors, and their estimation process in the context of INS processing flow. These errors have a serious impact on overall inertial system performance. The results of undertaken researches in that area, and pointing out the main difficulties behind the INS when using a few top MEMS technologies, were presented as well. The paper clearly states, that current MEMS technologies, including sophisticated software, does not fulfil submerged inertial navigation whilst operating in dynamic conditions, due to linear acceleration, affecting gyro performance.