How accurate is trackman and GPS?

[surefire]

Just wondering, does anyone know how accurate trackman is?

How much difference does it make if the trackman is used indoors into a net, instead of seeing the full flight?

My main reason for asking is I recently had an indoor session on a trackman, and with my current driver it was showing a total distance that seemed not massively, but a little bit short to me.

I then went out and played 9 holes and measured every drive with a GPS, and the average of these numbers was around 17 yards more than the trackman showed.
In fact the shortest into the wind was about the same as the trackman average and the longest with wind behind was about 55 yards longer.

Is this difference caused by GPS not being accurate, or trackman not being accurate indoors, or another factor entirely?

I'm not looking to boost my ego here, I'm looking to be able to feel confident that the trackman will help me get the best fitting club, or find an alternative (trackman outside perhaps?).

 

[G1BB0]

I would say trackman tbh, gps is accurate to within 3 metres or something similar

if its just used for driver then not a prob, if for irons into green then it makes a massive difference

played yesterday and Viscount used a dmd and the measurements were almost spot on for his iron choices, work it out for yourself

 

[Imurg]

Surely a DMD with a decent GPS component is going to accurate to a yard or 2.
But surely Trackman must be accurate too - the manufacturers and players wouldn't use it if it wasn't.
Maybe wind speed and direction played a bigger part than you'd think. Also the type of ball can make a huge difference. Was the trackman calibrated - if indeed it needs to be....?

 

[HomerJSimpson]

It depends on how the machine is set up and to be honest taking comparable readings in windy conditions isn't going to give accurate information. Lots of variable like the wind speed, air temperature and how wet the course is will all influence your on course information

 

[surefire]

No doubt wind came into it, but given that my shortest shot with wind against was the same as the trackman average, which was very consistent, I am still confused.
If the shortest shot had been shorter, then I would assume the wind was the difference.

The ball was the same type.

No idea about calibration, I know what they say about assumptions, but I did assume the guy operating the trackman knew what he was doing.

The fact pros and manufacturers use it also makes me wonder, although they normally use it outdoors, so it has a full flight to track, which my be the answer to my question.

Made me wonder though, so if anyone can confirm this, or has other suggestions, I am interested to hear.

 

[Losttheplot]

The GPS is more accurate in my opinion. The trackman can't allow for the constant change in OAT (outside air temp) and air pressures, wind speed and direction.
You might find if the exact settings on the trackman are replicated out on the course for OAT, wind, air pressure etc then the GPS and trackman might come up similar. Who knows.....

 

[surefire]

Having said all the above, if the trackman shows which set up gives the best ball speed (smash factor), launch angle and spin rate, does it matter if the distance on the machine doesn't 100% replicate the real world?

 

[Region3]

Was the distance you were looking at on Trackman the carry distance?

Obviously the GPS measured would be carry AND roll.
Just a thought.

 

[surefire]

Trackman gives both carry and total.

I realise there is no easy way for me to measure purely carry distance, so I just worked on the total difference.
To add to the confusion on this, the course was pretty wet, so it's not like there was an excessive amount of roll to skew my measured figures.