Measured, Calculated, Simulated: Tracing a Bad Number Back to Its Source

A bad number on a golf simulator usually comes from one of three places. The sensor may have seen something it could not read well, the unit may have calculated from incomplete data, or the software may have modeled the flight with settings that do not match your situation. Most owners blame the hardware first, but the chain is longer than that, and the error often starts before the ball reaches the screen.

This page follows one shot through that chain. It explains what each stage measures, why radar and camera units fail in different ways, and how to tell a misread from a genuinely poor strike. You will also find a few plausibility checks you can run on any number, built on ratios and rules of thumb rather than error figures. Tolerance specs are a separate question, covered in what accuracy specs and tolerances mean.

How we put this together: we compared published manufacturer specs, retailer listings and owner reports. Links on this page may earn us a commission.

The short answer: most bad numbers start before the ball reaches the screen

A launch monitor measures a small number of things directly and calculates the rest. A camera unit reads ball speed, launch angle, launch direction and, on many models, spin from a handful of images taken in the first few inches of flight. A radar unit reads the same core launch values from the Doppler track. Everything else on the screen, including carry, apex and descent angle, comes from a calculation, and the sim software then models the rest of the flight and the roll.

That structure matters because an error at the start of the chain does not stay put. A slightly wrong spin axis changes the flight model's curve, which changes carry, which changes where the ball lands relative to the simulated fairway. By the time the number reaches the screen, one bad input may have touched four or five outputs, and each of them looks equally confident.

The other half of the story is that many "inaccurate" readings are accurate readings of an unusual strike. A thin iron, a heel strike or a drive hit off the wrong part of the face all produce real, correct numbers. The skill is telling a sensor problem from a swing that simply did not produce a good shot. The rest of this page gives you the tools for that. If you want to know whether a number is physically possible, start with the checks further down. If you suspect the unit itself, the calibration fixes by symptom are a better next step than guessing.

Three stages every shot passes through

Every shot has three stages: the sensor captures it, the unit calculates launch data from that capture, and the software simulates the flight and the landing. The table below shows which stage is responsible for each metric and how the two main sensor types differ. "Typically" matters here, because models vary and some units do more or less in the sensor stage than others.

Metric	Typically measured by radar units	Typically measured by camera units	Usually calculated or simulated
Ball speed	Measured from the Doppler track	Measured from the first few images	Used as an input to carry
Launch angle	Measured from the track	Measured from the first few images	Used as an input to carry and apex
Launch direction	Measured from the track	Measured from the first few images	Used as an input to carry and offline distance
Spin rate	Measured on some units, estimated on others	Measured on many models from ball images, derived on others	Feeds the flight model
Spin axis	Measured on some units, estimated on others	Measured on many models, derived on others	Sets curve and side spin in the flight model
Club speed and path	Measured on some units, estimated on others	Measured with club markers or club imaging on some units, estimated on others	Feeds smash factor and face-to-path
Carry, apex, descent, total	Calculated from launch conditions	Calculated from launch conditions	Calculated with a ball-flight model
Rollout and course behavior	Not measured	Not measured	Simulated using the software's turf and green settings

Read the maker's documentation to see which metrics are measured and which are calculated on your unit. For a worked breakdown of one model, the Mevo+ data parameters guide shows the split. The split changes how you should read a number. A measured value is a direct observation, subject to the limits of the sensor. A calculated value inherits every assumption in the formula, and a simulated value inherits every assumption in the software.

Capture: what the sensor actually saw

Camera units take a handful of images in the first inches of flight. Those images are the raw material for everything the unit reports afterwards, so anything that disrupts them causes trouble. A ball that starts partly outside the field of view, a smudged lens, or a ball that moves before the frames are captured can all produce partial data. The unit then has less to work with, and in the worst case it reports numbers built from too few images.

Radar units work differently. They need the ball to fly far enough to build a track, and the track's length determines how much information is available for spin and launch. In a short room the track is short, which is the main reason indoor spin readings from radar can be less reliable than ball speed and launch. Our radar vs camera comparison goes into the trade-offs in more detail.

Missing a reading altogether is often better than a confident wrong reading. Some units flag low-confidence shots, and if yours does, treat a flagged shot as a candidate for removal rather than as a valid data point. Check your model's documentation to see whether and how it flags them.

Calculation: from a few frames or a trace to full launch data

The calculation stage turns the capture into launch conditions. Spin axis and spin rate may be derived from limited images or estimated from other values, so two units can report the same spin number through very different routes. That does not make either one wrong, but it does mean the reliability of the number depends on the route.

Estimated club numbers are a particular trap. A club figure can look precise to one decimal place without having been measured at all. If a unit does not capture the club directly, the decimal places describe the arithmetic, not the club. Before you trust a club metric for gapping or for a swing change, confirm whether it was measured or derived.

Simulation: the ball-flight model and course settings

Each simulation program applies its own aerodynamic model to the launch data. The model handles lift, drag and spin decay, and each developer tunes those choices differently. The same launch numbers can therefore show different carry in two programs. That difference comes from the model, not the hardware, and it is one of the most common reasons owners think their launch monitor is wrong when it is not.

Course settings add another layer. Altitude, temperature, wind, fairway firmness and green speed all change the result without any change in the swing. The same drive can look noticeably different at a sea-level setting and at a setting that matches a high-altitude course, and the sim will show that difference cleanly. Those settings are a choice, which also makes them a source of error if they do not match where you are playing.

See what accuracy specs really mean ↗

How radar and camera units go wrong differently

Radar and camera units fail in different ways, so the same problem can cost one type a little and the other type a lot. The table below lists the situations that most often cause trouble and how each technology responds. It is a guide to likely effects rather than a guarantee, because specific models and firmware handle the same condition differently. For a side-by-side look at the two technologies, see the radar vs camera comparison.

Situation	Effect on radar units	Effect on camera units
Short room	Less flight to track, so spin estimates have less to work from	Little effect, because the unit reads near the ball
Bright daylight or uneven room light	Little effect	Can lose the ball or misread it
Low ceiling	Changes positioning and overhead mounting height	Changes overhead mounting height and clearance
Ball type	Some units read spin more reliably with marked or metallic-dot balls indoors	Needs clean balls with clear markings; scuffs degrade images
Positioning	Must sit a set distance behind the ball and aim down the target line	Ball must sit inside the hitting zone beside the unit

Lighting is the clearest example. Radar does not need to see the room, so bright light or uneven shadows have little effect on it. A camera unit has to see the ball, and strong or uneven light can cause it to lose the ball or misread it. The lighting and interference guide covers which light sources matter and how to position them.

Room height is the other common constraint. A low ceiling changes how an overhead unit can be mounted and how much clearance the ball flight has, and for radar it can also change where the unit has to sit. If your room is tight, the low ceiling setup guide walks through the trade-offs.

Positioning is where many owners lose data without noticing. Radar units must sit a set distance behind the ball and aim down the target line. Camera units have a hitting zone beside the unit, and the ball has to sit inside it. The exact distances and zones come from each maker's manual, so check the documentation for your model rather than relying on a general rule of thumb. For camera units, the SkyTrak ball placement guide shows how to set up the zone correctly.

Ball type belongs in this comparison too. Some radar units read spin more reliably indoors with marked or metallic-dot balls, so check the maker's guidance for your model. Camera units want clean balls with clear markings, because scuffs and wear degrade the images they rely on.

What you hit, and what you hit it off

The launch monitor is only one part of the equipment. The ball, the surface and the club all shape the numbers, and some of those effects look like sensor errors. Work through this list before you assume the unit is at fault.

• Range balls and old balls. Range balls often fly and spin differently from premium urethane balls. Scuffed balls also give camera units poorer images, so a bucket of worn balls can make a good unit look unreliable.
• Cold balls. Cold balls lose ball speed. Balls stored in a cold garage can read short, so let them come up to room temperature before you compare numbers.
• Thin or hard mats. A thin or hard mat lets the club bounce into the ball, so heavy strikes read better than they would from turf. That is a real result of the mat rather than a sensor error, and it is one reason mat numbers and course numbers do not line up. The guide to matching sim practice with on-course results explains how to account for the gap.
• Club markers and stickers. Worn or misplaced stickers spoil club data on systems that need them. Check them before each session, especially after cleaning the bay.
• Tee height. Tee height changes launch and spin. A consistent tee height makes driver numbers comparable from one session to the next.

Room conditions that actually move the numbers

Room conditions split into two groups: the ones that change the data and the ones that only seem to. The real effects include the software's altitude and temperature settings, the temperature of the ball, room light for camera units, flight length for radar, and reflective surfaces inside a camera's view. Each of those can change a number you can see on the screen.

Connection problems are a different category. Wi-Fi or Bluetooth drops cause lag, disconnects and missed shots, but they do not usually produce wrong numbers. If a shot shows up late or not at all, the cause is most likely the connection. The Wi-Fi disconnect fixes cover the usual causes and the steps that tend to help.

Air movement is another common worry. A fan or a vent blowing across the bay has little effect on a shot that only flies 10 to 15 feet before it reaches the screen, because the simulator calculates the rest of the flight from the launch data. A fan is an unlikely cause of a wrong carry figure, so look at the settings and the strike before you look at the air.

The one thing you should not chase is a yardage correction per degree of temperature or per mph of breeze. Those effects exist in the real world, but they are not a dependable adjustment you can apply to a sim reading, because the sim's own model decides how conditions feed into the flight. If conditions matter to you, set the altitude and temperature the software offers and keep them the same across a comparison.

Misread or bad swing? Plausibility checks

This section is the one to use when a number looks wrong. None of these checks needs a calibration routine or a special tool. They use ratios and simple rules of thumb to ask whether a reading is physically possible, and they are good at catching misreads. They cannot tell you exactly how far off a number is, so use them to sort suspect shots from plausible ones, not to correct the data.

Smash factor: the first check

Smash factor is ball speed divided by club speed. With a driver, the practical ceiling is about 1.50. That ceiling comes from rules limiting how springy a driver face can be (the COR and CT limits), so a reading well above it, such as 1.55, points to a misread of club speed or ball speed rather than an unusually good strike.

Iron smash factors run lower than driver numbers. As a rough rule of thumb, a 7-iron reading above about 1.40 deserves a second look. It is a prompt to check the shot, not a hard limit, and the exact range varies by club and by how each unit reports club speed.

Carry per mph of ball speed

Carry in yards runs roughly in proportion to ball speed in mph. As an approximate rule of thumb, a well-launched driver often carries roughly 1.6 to 1.7 yards per mph of ball speed. That figure moves with launch, spin and conditions, so use it as a sanity range rather than a formula. By that yardstick, a ball speed of 150 mph should carry somewhere around 240 to 255 yards. A reading of 320 yards carry from the same 150 mph is implausible, and the first suspect is the ball speed reading.

Launch and spin should pair sensibly

Launch and spin move together in predictable ways for a given club. A very low launch paired with very high spin, or a wedge with almost no spin, suggests that one of the readings is wrong or that the strike was unusual. Check the other numbers for the same shot before deciding which one to believe.

Group patterns versus single shots

One wild shot in a group of consistent shots, with normal contact feel, is usually a misread. A repeating pattern, such as every shot curving the same way or every carry landing short, is usually the swing. A reading that looks like a sensor fault in isolation can be a real swing fault once it repeats.

Decision tree: misread or swing

Work through these questions in order:

1. Did the shot feel normal? If the contact felt clearly off, the number may be real, so check the strike and the swing before blaming the unit.
2. Is the smash factor plausible for the club? If not, suspect a misread of club speed or ball speed.
3. Does the launch match the spin? If the pairing is implausible, suspect the spin reading.
4. Does the carry fit the ball speed? If not, suspect the carry calculation or the speed reading.
5. If the shot passes all four checks, it is probably a real strike. Decide between a one-off misread and a swing issue by looking at the rest of the group.

Reading a session instead of a single shot

One shot tells you very little. Groups of shots tell you a lot, but only if you handle them the right way. Use this checklist to turn a session into numbers you can rely on.

• Hit groups of at least 10 shots per club before drawing conclusions. Smaller groups swing too much on a single misread.
• Use the median rather than the average, so one misread does not drag the number. The worked example below shows how much difference this makes.
• Remove only shots that fail the plausibility checks, not shots you dislike. Dropping shots because they felt bad is a way of making the data agree with your memory.
• Compare like with like: same club, same ball, same tee height, same software settings.
• Track trends across sessions. A gradual drop late in a session is often fatigue rather than drift in the unit, so note how many balls you had hit when the numbers started to slide.

Worked example: building 7-iron numbers you can trust

This example uses an illustrative set of ten 7-iron shots. It is not measured data from any unit, and it exists to show the arithmetic, not to tell you what a 7-iron does.

Eight of the shots are solid strikes, carrying 150, 151, 152, 153, 153, 154, 155 and 156 yards. One shot carries 171 yards with a smash factor of 1.48. One thin strike carries 128 yards and felt thin at impact.

1. Apply the checks. A smash factor of 1.48 is well above the rough second-look level of about 1.40 for a 7-iron, so the 171-yard shot fails the smash check. Remove it as a suspect reading. The club speed or ball speed for that shot is the likely culprit.
2. Keep the thin strike. The 128-yard shot felt thin, and that feel fits a real poor strike. Nothing in its data fails the checks, so it stays in the set. Dropping it only because it pulls the number down would be the same mistake as keeping the 171 only because it looks good.
3. Compare the averages. The average of all ten shots is 1,523 yards divided by ten, or 152.3 yards. Once the 171 is removed, the average of the remaining nine is 1,352 yards divided by nine, or about 150.2 yards. The misread shifts the average by about 2.1 yards.
4. Compare the medians. With all ten shots, the median is 153 yards. With the 171 removed, the median of the remaining nine is also 153 yards. The misread does not move the median at all.
5. State the result with its spread. For gapping, plan on about 153 yards for this 7-iron. The solid strikes span 150 to 156 yards, and the thin strike is a clear outlier at 128 yards. A carry figure with that spread is more useful than a single average, because it shows how much a good strike and a poor one can differ.
6. Remember what the number belongs to. This figure belongs to this ball, this mat and these software settings. Change any of those and the figure needs a fresh set of shots before you rely on it.

Software settings that quietly change results

Many owners never open the settings menu, yet those settings shape almost every carry number on the screen. Go through this list once, write down what you choose, and check it again after a software update.

• Altitude and temperature. Some programs default to sea level, while others let you match your home course. Set these to match where you play, or stay consistent with the setting you use for comparisons.
• Ball type, where the software offers the option. Choosing the wrong ball model changes the flight.
• Fairway firmness, green speed, wind and elevation in play mode. These change roll and landing more than they change the launch numbers.
• Normalized or practice-range modes. These can strip out conditions you may want to keep, so know which one is active before you compare numbers.
• Mulligans, auto-putt, gimme distance and auto-tee. These change how scores are recorded and how shots are placed, not how the ball flies.
• Units and columns. Confirm whether you are reading yards or meters, and whether a column shows carry or total distance.
• Firmware and app versions. Updates can change ball-flight models, so note the version when you compare numbers over time.

Before you blame the hardware

Run through this short pre-check before you contact support or buy new equipment. Many problems that look like sensor faults turn out to have one of these simple causes.

1. Re-run the maker's alignment or calibration routine from the manual. The steps differ between models, so do not substitute a routine from another brand's guide.
2. Clean the lens or sensor window and confirm the ball position. A smudged window or a ball set outside the zone can explain a run of odd numbers. The sensor cleaning and calibration guide covers the cleaning steps.
3. Swap to a fresh, clean ball, and keep using that same ball for the comparison.
4. Check the software settings in the list above.
5. Hit a group with a club you know well and compare the results with the carries you already know from the course.
6. If problems remain, use the symptom-by-symptom fixes on the calibration page, or contact support with a list of example shots that includes the time, club, ball and settings for each one.

Fix calibration problems by symptom ↗

Data questions sim owners ask

Owners ask the same handful of questions about data. The answers below explain the reasoning behind each one. For setting-specific steps, start with the checklists above.

Why does the same shot carry farther in GSPro than in E6 Connect?

Each program applies its own ball-flight model and default conditions, such as altitude, temperature and fairway firmness, to the same launch data. The launch monitor reading can be identical while the carry differs. Compare programs only with matched settings, and check either one against real on-course carries before deciding which is closer.

Is a driver smash factor above 1.50 a sign of a misread?

Usually, yes. Rules that govern driver design limit how springy a face can be, which puts the practical smash factor ceiling near 1.50. A reading well above that most likely means club speed was read low or ball speed was read high, so treat the shot as suspect and check the rest of its data.

Do range balls give worse readings than premium balls on a simulator?

They can. Range balls are often built for durability and may fly and spin differently from premium balls, and worn or dirty balls give camera units poorer images. Some radar units read spin more reliably indoors with marked or metallic-dot balls, so check the maker's guidance for your model. Use the same clean ball for any numbers you want to compare.

Why are my indoor carry numbers longer than on the course?

Several things usually combine. Mats forgive heavy strikes by letting the club bounce into the ball, software defaults may not match your course altitude or temperature, and the sim has no wind or uneven lies. On-course yardages also include misses you do not repeat on the mat. Treat the gap as a known offset rather than a sign the unit is broken.

How many shots does a club average need before it can be trusted?

A group of at least 10 shots per club is a practical minimum, and a larger group gives a steadier median, especially for long clubs. Use the median rather than the average, remove only shots that fail plausibility checks, and keep the ball, tee height and software settings the same across the group.