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Waypoint Inertial Explorer™
Inertial Explorer (GPSIMU) post-processing software suite is aimed at users who wish to integrate rate data from six degrees of freedom IMU sensor arrays with GPS information processed via Waypoint GrafNav, which is included. Waypoint Inertial Explorer is designed to utilize strapdown accelerometer (Dn) and angular rate (Dq) information to produce high rate coordinate and attitude information from a wide variety of IMUs, including high-accuracy navigation grade to inexpensive MEMS (Micro Electro-Mechanical Systems) sensor types. Waypoint Inertial Explorer runs within the familiar Waypoint GrafNav processing environment and data analysis is performed with the same plotting tools. This provides Waypoint Inertial Explorer with all of the same features available in GrafNav. Waypoint Inertial Explorer can bring GNSS and IMU data together two different ways. In loosely coupled processing the GPS data must first be processed in order to store optimal position, velocity and quality information in the standard Waypoint GrafNav fwd/rev/cmb files. Following this, the IMU component of Inertial Explorer can be invoked to perform alignment, mechanization of measurements and filtering. GPS coordinate and velocity updates are implemented by time matching and interpolating the inertial rate data with the closest GPS measurement epoch. Loosely coupled processing is suggested for opens sky surveys, including airborne applications such as LIDAR or photogrammetry. In tightly coupled mode, the GNSS and IMU data are processed simultaneously. Benefits of tightly coupled processing include the application of phase updates which limits inertial error growth when even two GPS satellites are available, as well as through automatic ZUPT detection. Tightly coupled processing is suggested for poor signal tracking environments such as ground vehicle surveys in urban environments. It is the user's responsibility to time tag each set of inertial measurements to the GPS time frame during the data collection process. NovAtel's SPANT Technology offers this. For more information on SPAN, click here. Waypoint Inertial Explorer is aimed principally for SPAN users or those who wish to OEM their own GPS / inertial hardware platforms and process that data in a production level software environment. It is not designed to replace the very fine commercial level GPS/Inertial systems which are available.  Figure 1 Forward/Reverse attitude separation (LN200) 
Figure 2 GPS-IMU position difference (LN200) |
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