Why GPS Update Rate Matters in eFoil Racing

Understand the difference between 1 Hz, 10 Hz and 25 Hz GPS, and why update rate affects eFoil timing, turns and speed measurements.

What does GPS update rate mean?

GPS update rate describes how often a receiver produces a new position or navigation solution. It is normally shown in hertz. A receiver operating at 1 Hz produces approximately one update per second, while 10 Hz produces approximately ten updates per second.

The update rate does not automatically guarantee accuracy. Antenna quality, satellite visibility, filtering, signal reflections and the receiver itself also matter. However, more frequent valid samples can describe a fast-moving path in greater detail.

How far does an eFoil travel between samples?

At 40 km/h, a rider travels about 11.1 metres per second. At 50 km/h, the distance is about 13.9 metres per second.

• 1 Hz at 40 km/h: roughly 11.1 metres travelled between updates.
• 10 Hz at 40 km/h: roughly 1.1 metres travelled between updates.
• 25 Hz at 40 km/h: roughly 0.44 metres travelled between updates.

These figures describe distance travelled between samples, not a guaranteed positioning error. They show why a low update rate gives timing software fewer points with which to reconstruct a fast turn or finish crossing.

Why turns are especially demanding

A straight line can often be estimated reasonably between two samples. A tight apex turn is more difficult because direction and speed can change rapidly. With only one point each second, the recorded line may cut across the real curve or miss the exact point where the rider changed direction.

More frequent samples can provide a clearer picture of turn entry, apex location, speed loss and exit direction. This is particularly relevant to an out-and-back race where the turn is a major part of the total time.

1 Hz versus 10 Hz versus 25 Hz

1 Hz

One update per second is common in many consumer devices and can be adequate for recording a general track. It provides relatively few samples during a short, fast competition run.

10 Hz

Ten updates per second provide much denser movement data. This can improve the representation of the apex and the estimated moment a virtual line is crossed, provided the samples themselves are reliable.

25 Hz

Twenty-five updates per second provide even finer time spacing. The benefit depends on receiver quality, configuration, communication stability and the timing logic using the data. A high rate cannot repair poor satellite reception or incorrect positions.

Can software interpolate between GPS points?

Yes. Timing software can estimate where a path crossed a virtual line between two measured points. Linear interpolation uses the positions and timestamps around the crossing to estimate the crossing time more precisely than simply choosing the nearest sample.

Interpolation works best when the movement between the points is predictable. More frequent samples reduce the distance over which the software must make that estimate.

How to get better GPS data on the water

• Allow the device to establish a stable satellite position before starting.
• Keep the phone or receiver where its antenna is not heavily shielded.
• Use the correct location permissions and disable aggressive battery restrictions where required.
• Avoid testing close to large structures that may reflect or block satellite signals.
• Confirm that an external GPS remains connected before beginning a run.

For the complete process, see how Apex250 detects and times a run.