How to compare laps with telemetry

Compare laps by position, read the time difference, and check braking, entry and exit evidence without mistaking a GPS difference for a driving change.

By Purple Sector. Published and reviewed 29 September 2026.

Open your own file See a sample debrief

Lap 6 picked against lap 1: the gap to lap 1 at every turn on the map, T3 the largest at +0.87 s. — Shown: a real MyChron 5 session at Queensland Raceway National. A file from any logger Purple Sector reads opens in the same view.

Compare the same course and timing basis

A telemetry comparison measures the difference between two recorded laps. Start with the same circuit layout and direction, then check that both laps are complete and use a comparable timing point. Purple Sector aligns usable laps by their recorded route; different layouts or incompatible GPS paths are not evidence of a driving improvement.

The same length in the opposite direction is still a different course: One Raceway (Wakefield and Shelley) and Norwell Motorplex (Circuit and Anticlockwise) each have two layouts like that. Some venues have many recognised layouts: Morgan Park Raceway has 11, The Bend Motorsport Park has 8, Euromarque Motorsport Park (Ruapuna) has 6 and Queensland Raceway has 5. Check the layout name on both laps.

Open a session and choose a reference

Open the original logger recording or a full-session export. Check the lap list and any timing or data-quality warnings.
Select the lap you want to understand and a valid reference lap. A quicker lap from the same recording is a useful first comparison.
Read the time-difference trace alongside speed and the GPS map. Look for where the gap changes, rather than only the final lap-time difference.
Inspect the channels actually recorded around that corner. Use braking, throttle or steering only when the corresponding channel is available.
Keep a note of the finding and a specific change to evaluate in the next session. A different result is not automatically caused by that change.

What does the delta trace mean?

The delta trace shows how the elapsed-time difference changes as the laps progress along the comparison. A growing gap identifies a place to investigate. It does not, by itself, tell you why the loss happened. Check the lap labels and displayed sign convention before deciding which recording is ahead.

A lower entry speed, different corner path or slower exit can all affect the downstream time gap. Examine the approach, corner and following straight together. Conditions, traffic, a tow and logger quality can also change what a comparison means.

Can I compare different sessions?

Purple Sector can offer eligible sessions from your library for comparison at the same layout. GPS paths must agree sufficiently for a position-based comparison. Check the recording quality and timing basis, and retain any uncertainty the workspace reports. A comparison being available does not prove that tyres, weather, traffic or setup were equivalent.

What should I check before trusting a finding?

Both laps cover the same route and direction.
The timing point, lap completeness and time basis make sense.
The reference is representative of the question you are asking.
The relevant channel is measured, or the interface clearly labels its estimate.
The difference is larger than the uncertainty described for the recording.

Guides by logger: AiM (MyChron, Solo) · RaceBox · VBOX · RaceChrono · Harry's LapTimer · TrackAddict · MoTeC · Garmin Catalyst · GoPro · Alfano.