Last updated: August 28, 2026
The Garmin R10 reads short indoors because it never sees enough ball flight to measure spin. It calculates spin instead, and that calculated spin feeds a carry model that trends short. Before spending money on marked balls or a new unit, a free ten ball speed test tells you whether the gap is the machine's math or your strike on the mat.
Outdoors, the R10 tracks the ball long enough to measure spin from the actual flight. Indoors, the ball hits the net in a few feet. The unit never gets a real spin reading, so it calculates spin from the launch conditions it can see (ball speed, launch angle, and whatever partial flight it captures).
This matters because carry is downstream of spin. A 7 iron that should spin around 6,000 to 7,500 rpm (Trackman tour averages) can come out modeled well below that band indoors. Lower modeled spin means a flatter modeled trajectory, which means shorter modeled carry. The error compounds with hang time: a wedge barely has room to be wrong, while a driver has all day. That is why the classic indoor radar report is "driver short, wedges perfect."
Direction bias and distance shortfall are two separate problems. A consistent one way direction miss is an aim story before it is a swing story.
The R10 reads launch direction relative to the line the unit is aimed at, not your stance, your mat, or your net. If the device faces left of the actual target line, it reports every shot right of where the ball actually went. Garmin's own manual states this directly.
Garmin's alignment check is simple: lay a club or alignment stick on the ground between the unit's alignment line and the ball. Both should point at the same target. If they diverge, rotate the unit, not your stance.
If your direction is off, fix the aim first. It has nothing to do with the distance problem, and fixing one while the other is wrong makes both harder to diagnose.
Ball speed is the R10's most trustworthy number. Garmin specs it within about a mile an hour of Trackman, and it does not lean on the flight model at all. That makes ball speed the free arbiter. If your ball speed matches across locations, you know the swing is the same and the carry gap is all downstream modeling. If it does not, no purchase fixes a strike that changes on a mat.
| Ball speed gap | What it means | What to do |
|---|---|---|
| Within 1 to 2 mph | Your swing is the same in both locations. The carry gap is the R10's indoor spin model. | Marked balls (Titleist RCT) are the targeted fix. They correct the spin model directly. |
| 4 to 5 mph slower indoors | Your strike changes on the mat. The mat may forgive a heavy contact the course would punish, or the confined space may change your swing. | Work on strike quality on the mat before spending on equipment. No launch monitor upgrade fixes a different swing. |
| 2 to 3 mph difference | Ambiguous. Could be a small strike change, normal unit variance (two units a mile an hour apart is typical), or both. | Retest on a different day. If it stays, lean toward a mild strike gap. If it closes, it was noise. |
This test costs nothing except a sim bay rental you were probably going to use anyway. And it answers the question every forum thread argues about: is it the R10 or is it me?
Two separate gaps stack on top of each other, and they pull carry in the same direction.
| Club | Typical indoor spin range (Trackman tour avg for reference) | Modeling gap risk | Strike gap risk |
|---|---|---|---|
| Driver | 2,000 to 3,000 rpm | High (long hang time) | Low (teed up, mat irrelevant) |
| 7 iron | 6,000 to 7,500 rpm | Moderate | Moderate (mat forgives heavy contact) |
| Pitching wedge | 9,000 to 11,500 rpm | Low (short hang time) | Low (short swing, less margin for error) |
If your driver reads short but your wedges are accurate, the modeling gap is dominant. If your mid irons read long at home but short on the course, the strike gap is in play. The ball speed test separates them.
Marked balls are the most effective single fix for the indoor modeling gap. Garmin's claim for the Titleist RCT integration is up to 30 times better spin accuracy and up to 50 percent better carry accuracy indoors. Those are manufacturer numbers, not independent tests, but the mechanism is sound: RCT stands for Radar Capture Technology, a marker built into the ball that the R10's radar can actually read, so the unit measures spin instead of modeling it from launch conditions alone.
This only fixes the modeling gap. If the ball speed test showed your strike changes on the mat (4 to 5 mph slower indoors), marked balls measure that same worse strike with better spin data. The carry number gets more accurate, but it still reflects the worse contact. That is not a bad thing. Accurate data you can trust is better than inflated data that feels good.
RCT balls cost more than practice balls, and you do not need a bucket of them. A sleeve kept for testing and benchmarking covers it, because ten solid strikes establish a baseline.
Cranking the altitude setting until your carry numbers look right relabels the number instead of correcting it. The R10 applies a thinner air model (ball carries farther in thinner air) to offset the indoor shortfall. Your 7 iron now shows 165 instead of 155.
The problem: you no longer know what your 7 iron does. The number on screen is not your carry. It is your carry plus a fudge factor tuned to make one club look right, which over or under corrects every other club because the modeling gap is not uniform across the bag. When you take those distances to the course, your gapping will be wrong in unpredictable ways.
If your indoor numbers are consistently short and you know the modeling gap is the cause (the ball speed test matched), fix the input (marked balls) or accept the offset and plan accordingly. Do not fix the output.
A camera based unit (a GCQuad, a Uneekor, the Foresight and Bushnell family) reads the ball in the launch window using high speed cameras instead of extrapolating the full flight from radar. Indoor carry becomes steadier because the spin measurement does not depend on how far the ball travels after launch. For a deeper look at which numbers are measured and which are estimated across different launch monitor types, see the measured vs estimated accuracy guide.
But a camera unit is not a magic fix. If the ball speed test shows your strike changes on the mat (slower ball speed indoors), a more precise unit only measures that same worse strike with more precision. You get a more accurate picture of a problem that lives in your contact, not your equipment.
The honest sequence: run the ball speed test, fix alignment, try marked balls, and then decide if the remaining gap justifies the upgrade. Most golfers find that RCT balls close enough of the modeling gap that the upgrade becomes a want, not a need.
Disclosure: I built Fore-ward Thinking and its AI coach Chip to automate the remember and recap part of this process. Once you establish your real baselines (ball speed, carry, spin by club), Chip reads your launch monitor data across sessions and tells you what changed and what to work on next. It coaches from your data, not swing video, and it works with any unit that exports numbers. You can try it free with no card.
Why does my Garmin R10 read short indoors but not outdoors?
Outdoors the R10 tracks enough ball flight to measure spin directly. Indoors the ball hits the net before the unit can read spin, so it calculates spin from launch conditions. That calculated spin feeds a carry model that trends short, especially with longer clubs where hang time gives the error more room to compound.
Do marked balls like Titleist RCT fix the indoor distance gap on the R10?
Marked balls are the most effective single fix. Garmin claims the Titleist RCT integration delivers up to 30 times better spin accuracy and up to 50 percent better carry accuracy indoors. The RCT marker is one the R10's radar can actually read, so the unit measures spin instead of modeling it from launch conditions alone.
Should I adjust the altitude setting to fix my indoor carry numbers?
No. Cranking altitude until carry looks right relabels the number instead of correcting it. Your 7 iron will show the yardage you want, but you will no longer know what your 7 iron actually does. When you take those numbers to the course, your gapping will be wrong.
How far should the R10 be from the ball for indoor use?
Garmin specifies 6 to 8 feet behind the ball, with at least 8 feet from the ball to the net. Outside that window, readings get less reliable, so check the spacing before blaming the unit or your swing.
Will upgrading to a camera based launch monitor fix my indoor numbers?
A camera unit reads the ball in the launch window instead of extrapolating the full flight, so indoor carry becomes steadier and less dependent on a spin model. But if the ball speed test shows your strike changes indoors (slower ball speed on the mat), a more precise unit only measures that same worse strike more accurately. Fix the strike first.
Keep going:
Pick your launch monitor and setup to see which numbers it measures, which it estimates, and which you can safely coach off, with the maker's own accuracy figures where they publish any.
A plain English guide to reading the ball and club flight numbers your launch monitor feeds into GSPro, and what "good" looks like club by club.
A measured loop of baseline, work, retest, and log, with beginner, intermediate, and advanced versions and a printable session template.
Clear definitions for every number your monitor reports: smash factor, club path, spin, face to path, angle of attack, and more.