Focusing on mobile mapping applications over the past several months we have looked at what is available regarding the GNSS component. Now it is time to move along to the INS. There seems to be considerable confusion and misunderstanding about the role of GNSS receivers in an INS. By this I mean it is often thought that the two were almost the same or that the GNSS receiver was the more critical part of the INS. The fact is, both are important and without either we are pretty much stuck in the pre-1980’s era. Let’s start by clarifying a few terms.
The GNSS, or Global Navigation Satellite System, is a system of satellites that provide 3D geo-positioning information (e.g. lat., long, elev.). As we have previously noted there are several GNSS working at least in part already. GPS is the most common GNSS and the terms are often used interchangeably in conversation.
The INS, or Inertial Navigation System, uses dead reckoning to compute the position, orientation, and velocity of an object using accelerometers, gyroscopes, and magnetometers. The position is relative to some arbitrary starting point. It does not require any external reference. Additionally, the INS is completely passive. It does not require input from any outside source (aside from the natural environment, most notably gravity). Often times, the term IMU – inertial measuring unit is used interchangeably with an INS, as defined.
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