Understanding The Magnetometer

Magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. (1) Though phonetically complex, magnetometers can be common devices used in everyday life such as compasses and metal detectors. In general, there are two basic types of survey magnetometers: vector and scalar magnetometers. Vector magnetometers measure magnitude and direction of a magnetic field. Alternatively, scalar magnetometers measure the absolute or vector magnetic field, using an internal calibration or known physical constants of the magnetic sensor.

What is a Point Cloud?

A point cloud is created by scanning an area with a 3D Laser Scanner. This scan is then imported into post-processing software (unless desired accuracy is obtained in real-time) where errors are removed. After processing the data, modeling software is used where the clouds can either be geo-referenced to a ground plane or manipulated locally without reference. From here, point clouds are then exported into computer-aided design (CAD) or building information modeling (BIM) systems, where they can be manipulated further, generating meshes and applying boundary conditions to generate accurate and realistic 3D models (1). Even with an explanation of a point cloud it is still hard to understand what a point cloud is if one has not been familiarized with the technology. When the user performs a scan, the laser scanner sends out beams of light in many different directions. As these light beams are reflected to the scanner, the system uses a datalogger to record reflected positions as localized vectors. These scan files can contain as little as thousands of logged vectors or as many as millions, if not billions depending on the scanning project at hand. These 3D vectors are then used in the post-processing software to generate a visualized point cloud.

Defining the Problem

For years Inertial Labs has produced high accuracy Inertial Navigation Systems (INS) at the world’s best price-performance ratio. An INS estimates the position, attitude, and velocity using the gyroscopes and accelerometers contained inside an inertial measurement unit (IMU). Position accuracy can be greatly improved when the INS is aided by Global Navigation Satellite System (GNSS). However, GNSS is not always available. Customer requirements demand for better performance of an INS during a GNSS outage. Outages can be caused by tunnels, urban canyons, roads under bridges, etc. 

What is Sensor Fusion?

Sensor fusion plays a large role in any device that is attempting to produce estimated, quantifiable data. Sensor fusion is the ability to bring together inputs from multiple sensors to produce a single model whose result is more accurate than that of the individual inputs alone. There are three fundamental methods of sensor fusion:

• Redundant Sensors- All sensors give the same information for the environment.
• Complementary Sensors- The sensors provide independent, disjointed information about its environment.
• Coordinated Sensors- The sensors collect information about its environment sequentially.

From there, the information is communicated in one of three different ways. In a centralized setup, all sensors provide information to a common central node. If the configuration is decentralized, no information is communicated between the sensors and the nodes. If it is a distributed organization, then the nodes interchange sensor information at a given rate.

History of Marine Navigation

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