One of the most important factors to consider when purchasing a launch monitor is where you plan to use it.
Indoor practice places very different requirements on a release monitor than outdoor use. With limited ball flight, accuracy depends on how well a device measures launch angle, spin rate, ball speed and carry distance without relying on extended flight to mitigate errors.
Using the GCQuad as a benchmark, we compared several personal launch monitors based on average percentage difference indoors. When looking at all four key metrics together, three models consistently stayed closer to the baseline data than the rest, while one clearly lagged behind.
Internal precision results (Mean % Difference vs. GCQuad (Internal))
| Start Monitor | Launch angle | Rotation speed | Keeping your distance | Ball speed |
|---|---|---|---|---|
| GC3 forecast | 3.5% | 2.0% | 1.5% | 0.4% |
| Garmin Approach R50 | 2.5% | 1.5% | 2.2% | 0.3% |
| Rhapsodo MLM2PRO | 1.5% | 1.5% | 1.4% | 0.3% |
| Start Master Pro | 24% | 17-18% | 5.5% | 4.4 |
GC3 forecast
GC3 yielded some of the most internally consistent results in the data set.
Along the launch angle, spin speed, carry distance and ball speed, GC3 stayed within a tight range with no significant spikes. This stability is important indoors where even small launch or rotation errors can distort transport distance and clearance.
If you want internal data that requires minimal interpretation, GC3 set the standard here. It was also the runner-up for the best overall release monitor in 2025.
Garmin Approach R50
of Garmin Approach R50 performed on a par with the GC3 indoors and, in some categories, showed even smaller average differences.
Launch angle and spin rate stayed particularly tight while ball speed and carry distance remained well controlled. most importantly, R50 avoided the kind of one-metric outliers that can undermine confidence during indoor practice.
From a data point of view, R50 proved to be one of the most balanced internal performers in the group.
Rhapsodo MLM2PRO
When you look at all four tables together, MLM2PRO consistently posted some of the lowest average margins relative to the GCQuad, often matching or exceeding the most expensive indoor units.
Launch angle and spin rate were among the strongest measured. Carry distance remained closely tied and ball speed was tied with the top performers in the test.
Based strictly on internal accuracy, MLM2PRO earned its place in the top three and the price can’t be beat.
A release monitor stuck inside
of Swami Launch Master Pro was broken for wrong reasons in internal release monitor testing.
It showed the largest indoor average differences in launch angle and spin speed and those discrepancies made to maintain distance and ball speed. Indoors, where launch and spin are fundamental data, this level of variance makes trend-based practice much more difficult.
Compared to the top performers, the gap here was significant.
The final take
If your goal is reliable internal practice data that you can trust, the breakdown in these numbers matters, and testing makes that breakdown clear. Here’s a look at our full launch monitor 2025 test: The best launch monitors of 2025.
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