How to compare ski runs using video and GPS data

In alpine ski racing, improvement often comes from small differences. Comparing ski runs allows coaches to identify where those differences occurred and understand what caused them.

Video shows what the athlete did. GPS athlete data shows where performance changed. When both are linked, comparison becomes precise rather than impression-based.

If you are new to GPS athlete data, start with GPS ski analysis explained for coaches before going deeper into comparison methods.

Step 1: Choose the right comparison reference

Every comparison begins with a reference. The reference defines what “ahead” and “behind” mean.

• Fastest overall run. Useful in training when identifying what separated the top performer.
• Best run for a specific athlete. Helps athletes compare against their own standard.
• Run number reference. Useful when snow conditions change through the session.

Changing the reference can change the story. A run that looks strong against one reference may show clear weaknesses against another.

Step 2: Identify where time was gained or lost

Instead of watching both runs from start to finish, begin with the time difference view.

• Locate expansion points. Where does the gap increase or decrease?
• Look for sustained trends. A steady loss across several gates often signals a tactical pattern.
• Separate noise from pattern. Small fluctuations are normal. Focus on meaningful sections.

This approach reduces guesswork. It directs attention to the parts of the course that actually influenced the result.

Step 3: Move from chart to video

Once a section is identified, jump directly to that location in the synchronized video.

• Compare entry line. Did one athlete carry more depth above the gate?
• Compare pressure timing. Who began accelerating earlier in the fall-line?
• Compare exit shape. Was the faster athlete set up more cleanly for the next turn?

In slalom, this might occur through a flush or delay. In giant slalom, it may happen above a pitch or transition. In downhill, it may occur across a terrain feature or glide section.

Relative vs absolute comparison

Comparison can be viewed in two main ways.

• Relative comparison. Shows how one run performs against another at each point on the hill.
• Absolute metrics. Shows each athlete’s raw speed or time progression independently.

Relative views are useful when identifying decisive sections. Absolute views are helpful when evaluating overall consistency or understanding how two athletes reached similar results through different strategies.

Both perspectives matter. Switching between them provides a more complete understanding of performance.

Section-based analysis with virtual splits

GPS athlete data allows flexible section placement anywhere on the hill.

• Define sections around terrain. Compare performance above and below a pitch.
• Define sections around combinations. Isolate hairpins or flushes in slalom.
• Maintain consistency across sessions. Reuse sections to track progress over time.

This flexibility goes beyond fixed intermediate splits and allows coaches to focus on the parts of the course that matter most in training.

Common comparison mistakes

• Watching full runs without direction. Always start with the chart to prioritize.
• Overreacting to small fluctuations. Focus on meaningful time differences.
• Ignoring course context. Consider terrain, snow condition, and set before drawing conclusions.

Comparison should support coaching judgment, not replace it.

Building a repeatable comparison routine

Strong teams use a consistent structure when comparing runs.

• Choose reference.
• Identify key sections.
• Review synchronized video.
• Explain cause and effect clearly.

This structure works across slalom, giant slalom, Super-G and downhill.

To see how this fits into daily training, visit How Protern Works. To explore the underlying capability, see Clear performance comparison.