How to Read Green Heat Maps

People call them heat maps. On a StrackaLine greens guide the color is not traffic, pin history, or a suggested start line. It is dual-view topographic slope in percent, taken from a laser scan that is accurate to the millimeter. The page also carries a 1-yard / 5-yard grid, plus hazards and sprinkler heads so you can orient the book to the green you are standing on.

Jim Stracka invented the laser-scanned green-reading map in 2007. The printed USGA version of that map is scaled no larger than 3/8 inch to 5 yards and bound at 4 1/4 × 7 inches. This article is how to read the percent and the fall line on that page. It is not a sample green from a named course, and it is not a recommended line of play. For the step-by-step on using the book in a round, use How to Read a Green Book and the how-to video.

The map starts as a scan of the putting surface, then prints as dual-view slope in percent.

What the colors and numbers actually are

Slope percent is rise over run, expressed as a percent. A 1% slope changes one unit of elevation across 100 units of distance. A 2% area is steeper than a 1% area. The number is a property of the surface through that part of the green. It is not “aim two cups out.” Two putts of the same length on the same percent can play differently if one is straight down the fall line and the other cuts across it, or if one is uphill and the other is downhill.

Dual-view means you are not looking at a single flattened picture. The guide presents topographic slope from more than one view so you can see how the surface changes through the area between the ball and the hole. Read the percent on the path the ball will actually travel, not only the number printed nearest the cup.

Because the scan is accurate to the millimeter, small shelves and ridges that do not show in a casual walk-around are on the page. That is the point of the product. It is also why you still have to stand behind the putt: the book can tell you the surface is there. It cannot tell you the pace you will put on the ball.

Fall line, high ground, and low ground

The fall line through a point is the steepest downhill direction at that point. Water would run that way. A putt hit along the fall line is mostly a speed putt — it is going straight down or straight up the steepest slope. A putt that crosses the fall line will move toward the low side as it travels. The farther you cut across a steeper percent, the more the ball has to be started on the high side if you want it to finish at the hole.

High ground is the side the slope climbs toward. Low ground is the side it falls toward. A ridge is a line of high ground with fall away from it on both sides. A collection area is low ground that several fall lines share. None of those words are a substitute for locating your ball and the hole on the 1-yard grid. The grid is how you stop reading the wrong part of the green.

Hazards and sprinkler heads around the green are printed so you can rotate the page until the book and the ground agree. If a bunker that sits short-right of the green is printed short-right on the page, you are oriented. If you have the page upside down, every percent you read is attached to the wrong place.

How to pick an aim from the map

Use the grid to place the ball and the hole. Look at the dual-view slope percent on the ground between those two points. Decide whether the putt is mostly along the fall line or across it, and whether you are going from high to low, low to high, or along a shelf. Then choose a start line and a pace. That last sentence is the player’s job. Rule 4.3 does not allow a map or a device to produce a recommended line of play based on the location of the ball. The book shows the surface. You pick the aim.

Do not invent a hole you have not scanned. A named course example that pretends to be a real green would be a different product than the book in your bag. Open the actual hole you are playing. The 13,000+ courses with full hyper-accurate green data are the ones where that page exists. The broader database is 31K+ courses; yardage can exist where a full greens guide does not. Check the store listing, as How to Order a Yardage Book describes.

A digital view of the same map has to stay at the same scale. Zooming the green past 3/8 inch to 5 yards, or asking the device for a line from the ball, is the phone version of breaking the rule. That is the core of Printed Green Book vs App. The paper size and scale language, including handwritten notes, is on What’s Legal? – USGA Rules.

Yardage pages are a different map

Distance rings, elevation tee to green, cover to bunkers and penalty areas, and a compass off the tee are yardage-book content. They help you hit the green. They are not a substitute for the dual-view slope page once you are putting. If you want both, order a combo. The product split is on Yardage Book vs Green Reading Book.

Checkout is on StrackaLine.com. Facilities use wholesale book pricing and facilities/info. College teams use the NCAA program. The rest of the library is on Resources.

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FAQ

Is a StrackaLine heat map a recommended putting line?

No. It is dual-view topographic slope in percent. You use the grid, the fall line, and the high/low of the surface to pick an aim. A recommended line from ball location is not allowed under Rule 4.3.

What does slope percent mean on the green?

It is how steep that part of the surface is. A higher percent is steeper. Combined with the fall line, it tells you whether the putt is uphill, downhill, or moving toward the low side as it rolls.

Why are sprinkler heads on a green map?

Orientation. Hazards and sprinkler heads let you rotate the book until it matches the green in front of you. They are not extra targets for the putt.

Can I zoom a digital heat map to see more break?

No. Digital putting-green images must stay inside the same 3/8 inch to 5 yard scale limit. Enlarging the green past that limit breaches Rule 4.3.