Here is the methodology used in creating the heat chart showing where passing plays have been most and least successful near the end zone.
The football field is 160 feet wide, so there are 16 zones represented horizontally. I tried to eyeball the location based on reviewing the film, but it is just an estimate. The zones may not be exactly equal, because I divided the field into larger zones for ease of marking locations, especially in end zone where there are no hashmarks. Those zones are:
- “Outside and Including the Numbers”, both left and right (42 feet each), which includes the sideline and three other boxes;
- “Between the Numbers and Hashes” (28 feet, 9 inches each), which is divided into three boxes, and
- “Between the Hashes” (18 feet, 6 inches), divided into two boxes, left and right middle.
Vertically, plays were divided into 2 yard increments, both in the end zone, and in the ten yards closest to the goal line. For example, this touchdown from Sam Bradford to Austin Pettis was categorized in the front two yards of end zone, left zone between the hashes. I tried to resolve ties toward the center of the goal line.
Also, I should point out that the zones represent where the intended target was at the time either the pass arrived or would have arrived. Think about bat downs and deflections. If a pass was deflected, for example, on a swing pass, I counted that as an incompletion to the zone where the receiver was, and not where the lineman touched it. The rationale is that we want to know success rates based on where the ball is intended to go. The same rationale applies to deflections and interceptions. A ball intercepted by a defender in the middle of the end zone intended to go to the back line would be counted against the back line zone.
THE RATINGS USED
The Red Zone chart shows the expected points added based on throws into zones. The colors go from red to lighter red to pink, then transition to blues, getting darker. The zones with red/pink represent those where expected points added is positive, merely knowing where a pass was targeted. The blue zones are those where expected points are negative (i.e., too many incompletions/short or no gains or turnovers to offset positive plays), with darker blue representing the lowest performing areas.
Using expected points allows us to account for not only touchdown rates, but things like interceptions and completions thrown short of the end zone that say, end up at the 1-yard line and improve the chances of a touchdown on the next play. Interceptions are rare (only six so far in these group of plays), but five of them have come between the numbers and five in the end zone. One of the reasons, we assume, that coaches like to throw designed fades and other passes to the outside is because of the lower risk of interception.
The data can be thin in specific 3 yard by 2 yard areas, as we are approaching 300 plays in an area a little over 1,000 square yards. To come up with the heat chart, the zones are an estimate using the specific square and the eight squares around it. (Think the Hollywood Squares box) The center square is weighted most heavily, and that point on the map really represents that square and all passes thrown within 2-3 yards of it in each direction. (With boxes on the sidelines, there were just fewer adjacent squares to use).
Here is a broader summary of the success rates in this area in 2013.