The Difference Between Heading and Course on a Fishfinder

If you’ve ever been spot-locked or barely moving and your map keeps spinning, it’s because your fishfinder is showing your course, not your heading. The two might sound similar, but they represent completely different things, and knowing the difference helps you understand what your fishfinder is really showing.

What Is Course?

Your course is the direction your boat is moving. It comes from your GPS tracking your movement over time.

If you’re idling forward, your course matches the direction your boat is pointed.
But if you’re drifting sideways or backward in the wind, your course points in that direction instead, even though your bow might be facing somewhere else.

That’s why your boat icon can act strange at slow speeds. When you’re moving unpredictably, your GPS signal constantly changes direction, and your fishfinder keeps reorienting the map to follow it.

If you’re sitting still, you actually have no course at all, your boat isn’t moving, so the unit can’t determine which direction you’re going. That’s when your map starts spinning or jumping because your GPS position is drifting slightly in random directions.

What Is Heading?

Your heading is the direction your boat is pointed, whether you’re moving or not.

Unlike course, heading comes from a heading sensor,  a small white puck with a built-in compass that reads your boat’s orientation.

Common examples include:

• Garmin SteadyCast

• Lowrance Point-1

• Humminbird AS GPS HS

A heading sensor tells your fishfinder exactly which direction the bow is facing at all times. So even if you’re sitting perfectly still, you still have a heading.
If you’re drifting backward, your heading stays the same (where the bow is pointed), while your course points behind you (the direction of travel).

Why You Need a Heading Sensor

If you don’t have a heading sensor, your fishfinder’s “heading” is actually just your course. That means:

• When you’re moving, the two line up and look fine.

• When you stop or move slowly, your map spins or drifts because the GPS is guessing your direction.

A heading sensor fixes that by giving your unit a constant directional reference. Your map stays oriented correctly even if you’re spot-locked, drifting, or sitting still.

Real-World Example

Let’s say you’re fishing a brush pile on spot lock.
Without a heading sensor, your boat icon spins in circles because your GPS position is drifting slightly as the trolling motor holds you in place.
With a heading sensor, your boat icon stays perfectly stable, pointed exactly where your bow is facing — so when you see a waypoint or brush pile on your screen, you know which way to cast every time.

The Bottom Line

• Course = the direction you’re moving (from GPS).

• Heading = the direction you’re pointed (from a heading sensor).

• If you’re sitting still, you have heading but no course.

• If you’re drifting backward, your heading stays forward but your course points behind you.

• Without a heading sensor, your unit displays course, not true heading.

• Adding a heading sensor keeps your map stable and your direction accurate, especially when spot-locked or fishing slowly.

If your map keeps spinning or your boat icon drifts when you’re not moving, a heading sensor is one of the most useful upgrades you can add to your setup.