GPS course vs compass heading

Movement and orientation

Course follows the journey. Heading follows the device.

A location course, called bearing in some APIs, describes the horizontal direction of travel at the time of a fix. If a cyclist moves north while holding a phone sideways, the course remains north. A compass heading describes the orientation of the device. The same sideways phone can point east while travelling north.

Navigation also uses a third direction: the bearing from the current position to a target or the next route point. That is calculated from two coordinates. It does not describe the current movement or the way the device faces.

An interface can draw any of these as an arrow. A triangle attached to the position dot often represents course when moving and compass heading when slow or stationary, but that is a design choice rather than a platform rule.

Direction of travel

Course becomes fragile as movement approaches zero.

A receiver or location provider can estimate course from GNSS velocity measurements, from change between positions or from a fused calculation. Android notes that a location speed may use satellite Doppler information and can be more accurate than simple distance divided by time. The method delivered to a particular app is not always exposed.

At a steady speed, successive movement provides a clear direction. At walking pace the signal is weaker, and when stationary there is no real direction of travel. Small position noise can make a calculated course swing even though the person has not turned. Platforms therefore attach availability or accuracy information to course where supported.

Course is useful once movement is established. It is a poor answer to “which way am I facing?” while standing at a junction.

Direction the device faces

Compass heading works while still, but brings different errors.

A phone or watch estimates orientation from magnetic and motion sensors. Magnetic heading is measured relative to magnetic north. True heading applies the local relationship between magnetic and true north when the platform has the information needed to do so.

Nearby magnets, steel structures, speakers, vehicles and electrical equipment can disturb the local magnetic field. Device tilt and sensor calibration also matter. A heading may therefore be available at a standstill yet point badly, while a course unavailable at that same moment becomes reliable after several seconds of steady travel.

The reported heading describes a device axis, not the person's eyes or handlebars. Holding a phone flat, upright or rotated can change how an interface interprets its orientation. Follow the app's presentation rather than assuming the top edge is always the reference.

At the junction

Match the arrow to the state you are in.

• Standing stillCourse may be absent or unstable. A valid compass heading can show orientation, subject to magnetic conditions.
• Moving steadilyCourse normally gives the clearest evidence of actual travel direction.
• Moving sideways or backwardsCourse and heading should differ because the movement and device orientation genuinely differ.
• Pointing at the routeThe bearing to a target can remain stable even when neither you nor the device faces it.

If an arrow behaves strangely, take a few deliberate steps in an open area and see whether it aligns with travel. Then rotate the device while stationary. That separates course-like and heading-like behaviour without claiming which sensor the app uses.

Map orientation is separate again. A map can rotate under a stable arrow or keep north fixed while the arrow turns.