Golf GPS technology... need opinions

[SubPar]

I have an iGolf which seems to indicate correct yardage and then drifts +/- 10-15 yards over a minute or two. I got this reply from their support guy. I am wondering if this rings true with other GPS users who may have different models.

" When standing still, fluctuation of yardage will occur. This is caused by the rotation of the earth, while you are locked onto satellites that are stationary. As it tries to refresh your position, you have moved slightly and the numbers will change. Usually, the signal is then switched to another satellite, and the fluctuation returns to the original readout.

Basically, the longer you stand in the same place, the less accurate the device is going to be. The most accurate yardage readout is found almost immediately after you arrive at your ball and stop walking. You can test this by walking or riding down the fairway, and checking the readout as you pass the 200, 150 and 100 yard markers. They should all give similar readouts as you pass by. When you arrive at your ball, check the yardage as soon as possible, and just remember what it says. "

Any opinions from GPS users would be appreciated.

SubPar

[TD22057]

That's a new one. The satellites are stationary? Right...

I'd say find a new support guy. The Earth is rotating, the satellite are moving, you're moving (maybe) so you'll never have a constant geometry or signal path. In general, you should get better results from standing still because the information in the measurements can accumulate in the filter. If a receiver's filter and noise modelling isn't done well, you could see a drifting of the solution.

FYI my SkyCaddie usually moves by 1-2 yards after coming to a stop but then stays on the same number.

[Diggitydog]

Man if this is true, I'm not wanting an iGolf. Does this happen with the Skycaddie? I played with a guy that had a skycaddie and I'm pretty sure it gave us a funkie yardage once, but other than that seemed pretty good.

[snoodlelvr]

I have an igolf as well. I've noticed the fluctuations too, but my findings are generally the opposite. After the adjustment, it's usually correct. I've done this when at yardage markers on the course to verify my position.

[SubPar]

That's a new one. The satellites are stationary? Right...

Well the satellites do move; their orbits are not perfect. And there are atmospheric conditions that influence the signals. (

very detailed info here ). After reading more about the technology, I am amazed they can ever be accurate to 1-3 yards. Some people have written that iGolf works great for them and I have not found a user review that mentions this particular issue. But I am wondering if Sky Caddie uses a more sophisticated receiver which does better error correction. This morning I was at the range again and set the iGolf on my bag while I was on the putting green. The yardage to a given point drifted from 137 to 119 and back up to 142 over a few minutes. From where I was positioned the 137 was probably right and that was the first number I got when I walked to that point; the drift came later. I am hoping to hear from more sky Caddie or iGolf users to see if this is a product-wide issue or maybe just my receiver. Here is an excerpt from an interesting piece on the www which may explain why an oridinary GPS is accurate enough for driving around or throwing 500lb bombs at buildings, but not for golf. "The principle of GPS is actually based upon super-accurate time signals, broadcast over radio waves from a constellation of 24 satellites circling the globe. At any given moment, at least three satellites will be within range of every point on the planet, permitting a GPS receiver to triangulate its position to within 10 yards or meters . Golf courses seek better accuracy than that and they use a modification of GPS called "Differential GPS". Differential GPS involves the use of one additional time signal... one broadcast from a ground facility situated on the golf course itself! So a golf course equipped with highly accurate GPS will actually have a stationary broadcasting unit affixed to a pole or tower somewhere on premises ." SubPar

[TD22057]

My understanding was that differential GPS isn't being used very much for golf courses (at least in the US). Most good receivers (I know SkyCaddie can at least) utilize the wide area augmentation system for improved accuracy. There's a pretty good write up of it here:

http://en.wikipedia.org/wiki/GPS_WAAS

[Billy_Baroo]

FYI my SkyCaddie usually moves by 1-2 yards after coming to a stop but then stays on the same number.

My Garmin GolfLogix also stays on the same number after briefly fluctuating a yard or two. Sounds like the OP got some BS customer service. Glad I didn't get an iGolf.

[Oliver C. Porkman III]

Man if this is true, I'm not wanting an iGolf. Does this happen with the Skycaddie? I played with a guy that had a skycaddie and I'm pretty sure it gave us a funkie yardage once, but other than that seemed pretty good.

I have the skycaddie. My experience has been positive. The only down side seems to be the batteries need to at or near full charge to work correctly. If I try to use it with a half charge it has a hard time aquiring and holding a signal. I have the SG3 model which uses regular batteries. I find I use it when playing away from my home course but I really don't need it on my home course.

[SubPar]

I followed the tech support suggestion and it seemed to work fine. I went outside my office with the iGolf and a laser range finder. I marked some positions and then moved around. If I took the iGolf reading when I arrived at a point, the distance was always within 2 yards of the range finder, which I know is very accurate. I checked readings from 30 yds to 182 yds.

I wonder if I am having poor reception at the range? The device usually struggles to get three satellites at the range, but at work it picks up 5 or 6 right away.

Thanks for the feedback. If this does not work out once I get it on a course, I'll probably send it back and get an SC3. I'll bet the Sky Caddie has better electronics inside.

SubPar

[Diggitydog]

So how often would you say a Laser Rangefinder is less useful than a GPS? If the rangefinder has a slope rating etc. other than hitting targets you can't see why would I bother with the GPS? Pros' / Cons' I guess.

[wolverine318]

So how often would you say a Laser Rangefinder is less useful than a GPS? If the rangefinder has a slope rating etc. other than hitting targets you can't see why would I bother with the GPS? Pros' / Cons' I guess.

Pros:

I would say a GPS is quicker One like the skycaddie gives you the shape of the green. Usefull for greens that you cant see all of it. Again gps usefull for blind shots and pins/hazads you cant see. Gives immediate distances to front middle back and to and over hazards Cons: You need batteries or to recharge the battery. Course needs to be in teh database unless you want to map it yourself. Although nobody I know has had this be an issue. No slope adjustment - not legal for use anyways in tourneys that allow these devices. Guys in my league have both, Ive played numerous times in the same group as players with a skycaddie and players with a rangefinder. Disances were never more than +-1 yard from each other. Size of both is comparable. GPS is slightly quicker to glance at than to aim. If you forget to charge or forget batteries yoru screwed though.

[SubPar]

Obviously the range finder has it's benefits... you can read distances to anything you can see. But the GPS would give you info you can't get with a range finder, like front and back of greens, or yardage to green center you can't see.

When I have used my range finder along side a GPS they have been within 1-2 yards. Since my swing at any point has a margin of error greater than that, I find the information useful.

Regarding my iGolf issues, I got a new USB cable and have been able to download courses. My yardage test based on the tech support suggestion was positive. I will try it on a course this weekend and report back, but I am optimistic.

SubPar

[SubPar]

Update:

I used the iGolf on two courses today and it performed very well. As the support technician suggested, when I am moving it is doing a good job of tracking my location and doing error correction. If I take my positional reading right when I get to the point I want to get yardage for, it appears to be well within expected tolerances.

On the course I was getting up to seven satellites. At the range where I was having trouble getting fixed readings I would only get 3-4 satellites and sometimes the signal would go weak.

iGolf is okay with me.

SubPar

[blue_crush]

heres one for you boys.......

I have some pretty high end GPS/PLOTTERS on my fishing boat. and even with 3 units I can be only as close as 10-30meters at times depending on the day...the military has the only really good GPS accurate to within 1meter.
my error see below_______________________________________________
and after 2000 the satilites were altered so you couldn't get a good fix, this was done so terrorest couldn't use gps units for bombing.....
___________________________________________________________
so with just standard tracking and the civilian satelllites how is it that a unit for just under 300.00 can be so accuarte.... bottom line is they can't.....I have a laser range finder and have stood next to the skycaddies and have found them to be off...its just that after the most guys hit there shots they didn't know difference anyway and just kept playing.

and think about this too, snippers out to 1000yds and more use a laser spoting scope to fix there target, gps only gets them to the area..

[TD22057]

heres one for you boys.......

While this was true some time ago, it's not true now. Selective availability (SA) (the signal degredation you're talking about) was turned OFF in 2000, not on. And - the military has announced that future satellites won't even include the capability to activate SA any more.

GPS w/ WAAS (which is available across the continentical US), is just fine for golfing. It provides ~ 1m accuracy more than 95% of the time. GPS has nothing to do w/ sniping unless we're suddenly shooting people who never actually move.

[blue_crush]

TD22057...I stand corrected,
text...
On Monday, the White House announced that the Global Positioning System (GPS) - the satellite transmissions used to pinpoint the location of aircraft, sea and land vehicles and even people worldwide - would become doubly accurate for the average person. Monday night marked the removal of selective availability (SA), a process that altered the signals received by civilian GPS users, making positioning accurate only to within 100 metres, while the military still had access to the undegraded signal accurate to within 20 or 30 metres. The "unscrambling" is being hailed as a big step forward for rescue operations and aviation safety.


this was in effect when units started using waas and multi SA tracking was becomming better, I agree... and now looking up the effectiveness of tracking devices like garmin who is a leader, they found that most unit were on average between 2-9meters which is about 6-30ft... which for most golf shots would be just fine. so yes I stand corrected....
its been awhile and I had forgotten that stuff, thanks for the reminder

[iacas]

on average between 2-9meters which is about 6-30ft... which for most golf shots would be just fine. so yes I stand corrected...

I disagree very much that 2-9 meters is "just fine" for golf shots. That's over 10 yards (or at least 2 or so) or a full club difference. That's horrible.

[blue_crush]

thats why I use a laser instead. I don't trust the gps and have seen them off and guys are wondering why there over/under.. my bushnell is fast and easy and I have had it awhile so its my go to yardage marker.