Reading dispersion ellipses — the tight oval and the big one
A dispersion ellipse shows you where a club's shots actually land on the range view: the tight ellipse (labeled 1σ in the app) rings roughly 2 out of every 3 shots for that club, and the big one (2σ) catches about 19 out of 20. ContactCoach draws them per club — toggle any club from the stats panel, or hit the "Ellipses" button floating over the range view to flip them all at once — and they're recalculated live from whatever shots are currently visible.
What do the two ellipses actually show?
Both ellipses are built from the same data: one point per shot, plotted by how far left or right it landed and how far it carried. The tight inner ellipse is a solid ring — about two-thirds of that club's shots should land inside it. The big outer ellipse is the filled, translucent shape around it — roughly 19 out of 20 shots should land inside that one. If you're regularly seeing shots land outside the big ellipse, that's usually either a genuine mishit or a session where that club had unusually high variance — either way, it's worth a look in the shot table.
How is the ellipse actually computed?
ContactCoach centers the ellipse on the average landing spot for that club's visible shots, then sizes it by how spread out those shots are — separately for the left-right direction and the carry direction. The exact numbers are in the box below if you want them.
For the nerds 🤓
The center is the mean carry and mean lateral of the club's visible shots. Radii are the standard deviation of carry and the standard deviation of lateral, computed independently along each axis:
1σ ring radii = (stdLateral, stdCarry)
2σ fill radii = 2 × (stdLateral, stdCarry)
This is an axis-aligned approximation, not a full statistical ellipse. A proper dispersion ellipse for correlated 2D data comes from the eigenvectors of the (lateral, carry) covariance matrix, which lets the shape tilt to match a diagonal miss pattern.
Because it's axis-aligned, the ellipse won't tilt to show a diagonal miss pattern — say, a swing that tends to go long-and-right on the same bad swings. It'll still catch that club's overall spread correctly, just not the diagonal shape of it. That's a deliberate simplification for a shape that has to redraw instantly every time you change a filter, and it's accurate enough to tell you which clubs are tight and which are loose. A version that tilts to match your actual miss pattern is on the roadmap.
Does the ellipse use the mean or the median?
The ellipse's size and position are based on the average and spread of your visible shots, recalculated live — again, a deliberate trade for a shape that has to redraw instantly. The catch is that averages are sensitive to outliers: one badly thinned iron shot in a session of fifteen can drag the ellipse's center and puff up its size more than it deserves, because a single bad shot moves an average further than it moves a median.
That's why, everywhere else in ContactCoach — like the carry numbers in the gap analysis panel — the headline distance for a club is the median rather than the average, with the "usual range" shown alongside it so a handful of mishits can't quietly distort the number you're supposed to trust. Median tends to be the better read on golf shot data because carry distributions are lopsided: a thin or fat strike costs you a lot more yardage than a great strike gains you, and that drags the average short. If a club's ellipse looks bigger or more off-center than where most of its shots actually cluster, that's the average getting yanked around by a few outliers — worth double-checking against the median carry in the stats panel or gap analysis panel before you draw any conclusions.
How do I use this in practice?
Turn on ellipses for one or two clubs at a time rather than your whole bag — six overlapping ellipses get noisy fast. A tight, round inner ellipse means a repeatable club; one stretched long along the carry direction means distance control is the leak; one stretched sideways means direction is the leak. Comparing ellipse size within a club type — irons against irons — tells you more than comparing a wedge to a driver, since longer clubs naturally spread more raw yardage even when they're just as consistent, relatively speaking.
Try it
Load your own session at /, or click "Explore a sample session" on that page, then toggle ellipses on a couple of clubs from the stats panel to see how tight your dispersion really is. Pair this with the gap analysis guide to see the median-based carry numbers that back up what the ellipse is showing you.