Dear Robert,
This device didn't strike me as all that useful. The two indicators are slope (in degrees, as opposed to percentage) and direction uphill.
Of these two, the more valuable is direction. The problem is that the read is only good for the spot where you place the gizmo. Also, the read is one of 16 arrows. Since you already know up from down, only 8 of these are meaningful. Because out of these 8, you can always ballpark the direction without the gizmo within about 3-4 of these arrows, what you are really getting is the benefit of help on picking among these 3-4 possibilities. About half the time, the gizmo fluctuates between two arrows, shifting back and forth instead of settling on one or the other. So you really aren't getting that much help with direction, and in any event, the help is only accurate at the spot where you locate the gizmo.
The instructions for use tell the golfer to place the gizmo "near the hole." That's good, because that is the most important of the many possible locations. I don't think the instructions make clear that using the gizmo at other locations is potentially harmful or confusing or meaningless (e.g., at the ball's location). This is the same problem with using the Harold Swash "green reader" UFO-looking spirit level, or indeed in using "plumb bobbing" to read surface contour (actually reads only where the golfer is standing).
The slope indicator is just a standard inclineometer with a readout in degrees precise to +/- 0.1 degree of slope. Most useful slope reads will fall between a fairly narrow range of 1 to 3 degrees. This is because green design for drainage requires a minimal slope and because too much slope doesn't work for high-Stimp greens in competition (balls won't stop rolling down). So basically there are 20 important possiblities of readouts for most occasions (1.1, 1.2, etc. .... 2.8, 2.9, 3.0 degrees).
These readouts could perhaps more usefully have been presented in terms of percentage of rise over run. A 3% slope is one that rises 3 feet for every 100 feet of run, or 3 inches for every 100 inches, etc. (If you squat at the low point of a green and look across to a high fringe 100 feet away, standing your 35-inch putter up, you can sight across the top of the putter with level gaze and the distant fringe will appear at that level.) This is the usual way survey engineers speak about land contours. There is a significant difference between a degree reading and a percent reading. For example, a 3% slope rises 3 feet for 100 feet of run, but a 3 degree slope rises 5.24 feet! A 2 degree slope rises 3.49 feet over a run of 100 feet. The degree measurement is steeper, and only yields an intuitively understandable number using trigonometry to convert degrees to percent in feet. The actual formula is tangent(degrees)*100 = slope in percent (feet).
Can the golfer really learn to recognize the difference between 2.2 and 2.4 degrees of slope in a meaningful way? Probably not. In psychometrics, the concept of "Just Noticeable Difference" (JND) is the empirical quantification of the human sensory ability to measure difference. For example, human visual accuity measure the width of the gap in the "flag" of letters like E and F at 20 feet (Snellen Wall Chart). On the 20/20 letters, this gap is as small as it can get for normal vision. (Example, hold a newspaper and read any newsprint-sized word with the letter "i" in it, and slowly push the paper farther away until the i transforms into an "l" -- your eyes can't see the gap anymore between the stalk and the dot of the "i" letter.) So even though the readout discriminates between 2.2 degrees slope and 2.3 degrees slope, can the golfer do this without the gizmo, when playing? Probably not. When you look down at the slope, what you really see is a surface that fills your field of vision. From this perspective, the cues to slope are the way the distinctive pattern of gradient in the surface (grass blades, shadows of grass blades, discolorations, etc.) appears to change in size and/or orientation as you look about within this otherwise uniform surface. Real slope detection does not limit itself to this sort of surface inspection, and golfers anyway are not well trained to rely upon this sort of analysis, except in a rough intuitive way that is not very good, consistent, or accurate. The slope is really read by a composite or ensemble of sensory processes that include the pressures in the feet, the body's orientation to gravity, the way the surface sits in relation to the surrounding scene, nearby cues to true vertical, comparing slope and contour here with the smoothness of changes as you look this way along the green to there, etc.
Regardless, just how well can a golfer tell the difference between slopes? I would imagine that what is a JND in reading slope at the hole from one green to the next (15 minutes later in another scene or on different days on the same green) is probably not better than being able to see a difference between 2.2 and, say, 2.7. Roughly speaking, this is the same as being able to see the difference between a 2% slope and a 3% slope.
Can the golfer use the gizmo to "train" the ability to recognize fine distinctions of slope? I'm sure it would help recognize the difference between a 2% and a 3% slope, but I'm also pretty sure it won't really help train the golfer to see the difference between a 2.2 degree and a 2.3 or even a 2.5 degree slope.
Earlier, I noted that the important readouts of slope fall between 1 and 3 degrees, for 20 possibilities. A golfer probably can't benefit from readouts less than in steps of 0.5 degrees. So, really, there are only about 5 slope readouts of any practical use (1.0, 1.5, 2.0, 2.5, and 3.0 degrees, which is equivalent to 1.75%, 2.62%, 3.5%, 4.37%, and 5.24%). That's something at least, but a lot less than the gizmo and its marketing hype claims.
Even if the gizmo can train a golfer to see the JND (about 0.5 degrees) more consistently and accurately, what help does that give him? The assumption of this technology is that an explicit recognition of slope can be used to visualize accurately the break. Actually, the green speed, the grain, the grass type, the surface conditions, direction of approach to the hole, and the environmental factors all come into play -- along with slope -- in accurately imagining the break at various points along the total path. So the gizmo is misleading, and implicitly invites golfers to try to make an association between a degree reading in tenths of a degree and small adjustments in imagining the curve of the break. That's pretty falacious and misleading.
The gizmo might be better used to help the golfer handle uphill / downhill adjustments in touch (distance or speed control) by building an associational "databank" in memory between a 10-footer downhill on a 2 degree slope and the same putt going uphill, or between a 2 degree downhill 10-footer and a 3 degree downhill 10-footer. But again, the extent to which the golfer can or ought to try to learn distinctions in slope is probably limited to about 0.5 degrees.
Technically, the direction and slope readouts depend upon how large the area of contact between the base and the surface, and how sensitive the gravitational detection. There are many inclineometers available. The one Adbul Bateman uses on the Buy.com Tour looks like a cigarette pack set on its edge longwise uphill and downhill, and gives a digital readout. He uses it about halfway between the ball and the hole on a 20-footer, either uphill or downhill, takes the number, and then works on his touch. I'm real sure he doesn't have any sort of so-called "muscle memory" for 20-foot touch for a 2.1 degree slope and another one for a 2.2 degree slope! Nor should he, since touch is specific for a day, a green, and a time.
If you want something that indicates direction uphill, I created the Mason Cap reader. It's a jar cap set upside down flat on the green with a little Evian water poured into it. The bead of water will show uphill / downhill better than the Exelys. If you HAVE to have a slope / incline reading, I created the Real Thing reader. Take a bottle of coke (or Evian water) with the fluid at a level in the straight middle section of the bottle; set the bottle on the green and see how much the water level slopes from low to high (look at the level sideways). If ther bottle is 3 inches in diameter at the water level, a 2 degree slope has 0.1 inch difference between the low and the high sides of the water level.
Here are some surveying websites if you can use them:
Land Surveying and Geomatics: On-Line Resources,
http://surveying.mentabolism.org/
Land Surveyor Reference Page,
http://www.lsrp.com/
SurveyPlanet.com,
http://www.surveyplanet.com/
Glossary of Surveying Units and Terms,
http://users.rcn.com/deeds/survey.htm
Geomatics,
http://pdh.biz/
U.S. Academy of Land Surveyors,
http://www.usals.org/
Surveyor Central,
http://www.surveyorcentral.com/
Surveyors.com,
http://www.surveyors.com/
Landsurveyors.com,
http://www.landsurveyors.com/
So, I personally wouldn't spend the $100 for an Exelys, but if I was given one I would use it out of curiosity but also use it carefully in light of what else is important in reading putts.
Cheers!
Geoff Mangum
Putting Theorist and Instructor
The PuttingZone.com
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