Augview Compass

Augview Compass is a high-accuracy compass application supporting:

• Compass Deviation Error measurement & correction

• Map navigation compass

• Augmented Reality compass

• Map marker tracking

• Works in all orientations

Have you been frustrated by Compass apps that claim to be accurate, but turn out to be hopelessly inaccurate or not work at all in certain device orientations? This was one of the drivers for us to create the Augview Compass app - a compass app that is more accurate, that works in all orientations and that provides both a map view and an Augmented Reality (AR) view for ease of use.

The accuracy improvement is achieved by first measuring the Compass Deviation Error, and then deriving a function that provides a correction for any observed bearing.

Compass

Your phone or tablet incorporates various sensors that may be used to determine its location, its orientation and the way in which it is moving. We can compute the compass orientation by using a combination of these sensors.

The magnetometer is the primary sensor used to detect magnetic fields. It measures the Earth's magnetic field in three dimensions (X, Y, Z axes) and helps determine the direction relative to Magnetic North. However, the Earth's magnetic field is relatively weak, and the magnetometers used in our phones show high levels of signal noise, when compared with the Earth’s magnetic field strength. To reduce noise in the outputs, filters and smoothing algorithms are used. To improve the accuracy, outputs from the accelerometer and gyroscope are also integrated using a technique known as sensor integration.

Using the outputs from these three sensors, filtering algorithms and sensor fusion, we can determine a bearing relative to Magnetic North.

The Magnetic North Pole is the point on the earth’s surface at which the planet's magnetic field points vertically downward. The magnetic north pole moves over time. As of 2024, its location is 86° N, 142° East and modelling predicts that by 2025, it will have drifted westward to 138° East.

True North refers to the geographic North Pole, the point at the top of the Earth’s axis where all lines of longitude converge. This is the northern point of the Earth’s axis of rotation. True North is essential for mapping and GPS systems, as it provides a consistent reference for determining direction regardless of magnetic variations.

The angular difference between Magnetic North and True North is called magnetic declination. This angle varies depending on where you are on Earth and because the north and south magnetic poles move, magnetic declination at a fixed point on the earth’s surface changes over time. Fortunately, there are formulae and web sites that can provide the declination value for any given date and geographic location. To indicate whether a bearing is relative to True North or Magnetic North we use the symbols °T or °M.

Compass Calibration

The operating system running on your device, allows you to Calibrate the magnetometer, to help reduce error, and to compensate for:

• Sensor Drift

• Local Magnetic Interference

• Sensor and phone manufacturing issues

To help reduce these issues, manufacturers recommend rotating the device about each axis, and/or rotating the device in a figure of 8 motion. Augview recommends a systematic approach where you:

• Face north to be parallel with the earth’s magnetic field flux lines (to get maximum and minimum magnetic field strengths)

• Rotate the device slowly about each axis twice

• Hold the device flat and rotate about the vertical axis twice

Calibration should be performed regularly, and especially after charging the device or leaving it near other electrical devices.

Compass Deviation Error

This is the error remaining after magnetometer calibration has been performed. The Augview Compass app incorporates a procedure for measuring and compensating for compass deviation error.