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. 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.

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 SPAN Technology offers this. For more information on SPAN, click here.

Figure 1 Forward/Reverse attitude separation (LN200)

Figure 2 GPS-IMU position difference (LN200)