# Stereo INS¶

The stereo-vision-aided Inertial Navigation System (INS) component is part of the sensor dynamics component. It combines visual-odometry measurements with inertial measurement unit (IMU) data and provides robust, low latency, real-time state estimates at a high rate. The IMU consists of three accelerometers and three gyroscopes, which measure accelerations and turn rates in all three dimensions. By fusing IMU and visual-odometry measurements, the state estimate has the same frequency as the IMU (200 Hz) and is very robust even under challenging lighting conditions and for fast motions.

Note

To achieve high-quality pose estimates, it must be ensured that sufficient texture is visible during runtime of the stereo INS component. In case no texture is visible for a longer period of time, the stereo INS component will stop instead of providing highly erroneous data.

## Self-Calibration¶

During startup of the stereo INS component, it will self-calibrate the IMU using the visual-odometry measurements. For the self-calibration to succeed, it is required that

• the rc_visard is not moving and
• sufficient texture is visible

during startup of the stereo INS component. Failure to meet these requirements will most likely result in a constant drift of the pose estimates.

## Parameters¶

The stereo INS component’s node name is rc_stereo_ins.

This component has no run-time parameters.

This component reports the following status values.

Table 14 The rc_stereo_ins component’s status values
Name Description
freq Frequency of the stereo INS process in Hertz. This value is shown as Update Rate in the Web GUI Overview tab in the Dynamics area
state String representing the internal state