Chapter 24 Quiz: Computer Vision and Tracking Data

Instructions

• 35 questions total
• Mix of multiple choice, true/false, and short answer
• Time limit: 45 minutes
• Passing score: 70%

Section 1: Tracking Data Fundamentals (10 questions)

Question 1

What is the typical frame rate for NFL Next Gen Stats tracking data?

A) 5 Hz B) 10 Hz C) 25 Hz D) 60 Hz

Question 2

In a standard tracking data schema, what does the 'orientation' field represent?

A) The direction the player is moving B) The direction the player's body is facing C) The angle to the nearest teammate D) The player's position relative to the line of scrimmage

Question 3

True or False: Tracking data typically captures positions for exactly 22 players plus the football on every frame.

Question 4

The standard football field in tracking coordinates is:

A) 100 yards long, 50 yards wide B) 100 yards long, 53.3 yards wide C) 120 yards long, 53.3 yards wide D) 120 yards long, 50 yards wide

Question 5

When standardizing tracking coordinates so the offense moves left-to-right, which of the following transformations is NOT typically applied?

A) Flipping x-coordinates B) Flipping y-coordinates C) Adjusting direction values by 180 degrees D) Changing player team assignments

Question 6

Short Answer: Explain why tracking data includes both 'direction' and 'orientation' fields. What different information does each provide?

Question 7

What is the primary challenge when calculating instantaneous speed from position data?

A) The math is too complex B) Noise in position measurements can cause unrealistic speed values C) Speed cannot be calculated from position D) The frame rate is too low

Question 8

True or False: A player's recorded speed in tracking data represents their velocity magnitude, not their directional velocity.

Question 9

In NFL tracking data, the y-coordinate value of 26.65 represents:

A) The goal line B) The center of the field (width-wise) C) The hash marks D) The sideline

Question 10

Which statement about tracking data frame IDs is correct?

A) Frame IDs are consistent across all plays in a game B) Frame IDs reset to 1 at the start of each play C) Frame IDs are timestamps in milliseconds D) Frame IDs correspond to TV broadcast frames

Section 2: Movement Analysis (10 questions)

Question 11

To calculate velocity components (vx, vy) from position data with frame rate f, the correct formula is:

A) vx = (x[t] - x[t-1]) * f B) vx = (x[t] - x[t-1]) / f C) vx = (x[t+1] - x[t-1]) / (2/f) D) vx = x[t] / f

Question 12

What is a reasonable maximum speed (in yards per second) for an elite NFL player?

A) 8 yards/second B) 10 yards/second C) 12 yards/second D) 15 yards/second

Question 13

When identifying a route's "break point," you are looking for:

A) The moment the receiver catches the ball B) The frame with maximum speed C) The frame where direction changes most sharply D) The first frame after the snap

Question 14

True or False: A receiver's separation is calculated as the Euclidean distance between their position and the nearest defender's position.

Question 15

Short Answer: Describe how you would calculate the total distance a player traveled during a play using tracking data.

Question 16

A "Go" route is characterized by:

A) Depth < 10 yards, significant lateral movement B) Depth > 15 yards, minimal lateral movement C) Moderate depth with a sharp cut toward sideline D) Short depth with immediate backward movement

Question 17

What metric best captures how evenly distributed a receiver's movement is between forward and lateral directions?

A) Speed variance B) Direction standard deviation C) Trajectory curvature D) Movement entropy

Question 18

When a defender is in "trail" technique on a receiver, you would expect:

A) Separation to be consistently large B) The defender to be positioned between the receiver and QB C) The defender to follow 1-2 yards behind the receiver D) The defender to mirror movements with constant separation

Question 19

True or False: Acceleration in tracking data is typically a signed value that can be negative when a player is decelerating.

Question 20

The concept of "time to contact" between two players requires calculating:

A) Just the distance between them B) Distance divided by the faster player's speed C) Distance divided by the closing speed (relative velocity) D) The integral of their speed difference

Section 3: Formation and Spatial Analysis (8 questions)

Question 21

What is the typical threshold for determining if a player is "in the box" defensively?

A) Within 3 yards of the line of scrimmage B) Within 5 yards of the line of scrimmage and between the tackles C) Within the interior 20 yards of field width D) Behind the defensive line but in front of safeties

Question 22

A "3x1" receiver alignment means:

A) 3 receivers total, 1 tight end B) 3 receivers on one side, 1 on the other C) 3 wide receivers in a triangle formation D) 3 receivers within 1 yard of the line of scrimmage

Question 23

Short Answer: How would you programmatically determine if a quarterback is in shotgun formation versus under center using tracking data?

Question 24

True or False: The convex hull of offensive linemen positions can be used to estimate "pocket area" for pass protection analysis.

Question 25

When analyzing defensive coverage, which spatial metric best distinguishes man coverage from zone coverage?

A) Average defender speed B) Correlation between defender and receiver movements C) Total defensive spacing D) Distance from line of scrimmage

Question 26

What does "offensive spacing" typically measure?

A) Distance between QB and receivers B) Average distance between all offensive players C) Width of the formation from sideline to sideline D) Depth of the backfield

Question 27

A pre-snap motion is detected in tracking data when:

A) Any offensive player moves before the snap B) A skill player moves laterally along the line before the snap C) The ball moves in the center's hands D) The defense shifts alignment

Question 28

True or False: Hash mark positioning (left vs. right) significantly affects optimal route designs and spacing.

Section 4: Visualization and Applications (7 questions)

Question 29

When creating an animated play visualization, the recommended approach for smooth playback is:

A) Plot all frames simultaneously with transparency B) Clear and redraw the entire figure each frame C) Update only the elements that change (artist updates) D) Generate individual image files and combine later

Question 30

What color scheme is most commonly used for football tracking visualizations?

A) Red for offense, blue for defense B) Team colors for both sides C) Green for fast players, red for slow players D) Consistent colors for positions regardless of team

Question 31

Short Answer: What are three essential elements that should be included in any football field visualization?

Question 32

When visualizing receiver routes, which representation provides the most information?

A) Just endpoints (start and end positions) B) Complete path with uniform coloring C) Path colored by speed or time D) Only the break point and final position

Question 33

True or False: Heat maps of player positions are most useful for analyzing single plays rather than aggregate tendencies.

Question 34

For real-time tracking visualization during a broadcast, the maximum acceptable latency is typically:

A) < 100 milliseconds B) < 500 milliseconds C) < 1 second D) < 3 seconds

Question 35

When building an Expected Yards After Catch (xYAC) model, which feature is typically MOST predictive?

A) Receiver's career YAC average B) Distance to nearest defender at catch point C) Receiver's speed at moment of catch D) Number of defenders between receiver and end zone

Answer Key

Section 1: Tracking Data Fundamentals

1. B) 10 Hz - NFL Next Gen Stats captures data at 10 frames per second.

2. B) The direction the player's body is facing - Orientation indicates where the player is looking/facing, which may differ from their movement direction.

3. True - Tracking systems aim to capture all 22 players plus the ball on every frame, though data quality issues can sometimes cause missing data.

4. C) 120 yards long, 53.3 yards wide - This includes both end zones (10 yards each) plus the 100-yard playing field.

5. D) Changing player team assignments - Team assignments are constant; only coordinates and angles need transformation.

6. Sample Answer: Direction represents the angle of movement (velocity vector), indicating where the player is going. Orientation represents the angle of the player's torso/body, indicating where they are facing. A player can be moving one direction while looking another (e.g., a QB rolling out while looking downfield). This distinction is crucial for understanding player awareness and predicting future movements.

7. B) Noise in position measurements can cause unrealistic speed values - Small position errors become amplified when calculating derivatives.

8. True - Speed in tracking data is the magnitude (scalar) of velocity, representing how fast without indicating direction.

9. B) The center of the field (width-wise) - The field is 53.3 yards wide, so 26.65 is the midpoint.

10. B) Frame IDs reset to 1 at the start of each play - Frame IDs are play-relative, making it easy to align data.

Section 2: Movement Analysis

11. A) vx = (x[t] - x[t-1]) * f - Velocity = (change in position) × (frame rate) since dt = 1/f.

12. C) 12 yards/second - Elite NFL speed is around 10-12 yards/second (about 22-24 mph).

13. C) The frame where direction changes most sharply - The break point is where the route changes direction most significantly.

14. True - Separation is the Euclidean distance: sqrt((x1-x2)^2 + (y1-y2)^2).

15. Sample Answer: Sum the Euclidean distances between consecutive positions for the player across all frames: distance = sum(sqrt((x[t+1]-x[t])^2 + (y[t+1]-y[t])^2)) for all frames t. Alternatively, you can integrate speed over time: distance = sum(speed[t] * dt).

16. B) Depth > 15 yards, minimal lateral movement - Go (or fly/streak) routes run straight downfield.

17. B) Direction standard deviation - Higher variance in direction indicates more varied movement patterns.

18. C) The defender to follow 1-2 yards behind the receiver - Trail technique has the defender chasing from behind.

19. False - Acceleration in tracking data is typically reported as magnitude (absolute value), though you can calculate signed acceleration from velocity changes.

20. C) Distance divided by the closing speed (relative velocity) - Time to contact = distance / |v1 - v2| where velocities account for direction.

Section 3: Formation and Spatial Analysis

21. B) Within 5 yards of the line of scrimmage and between the tackles - The "box" is typically defined as the area within 5 yards of LOS and within the tackle box.

22. B) 3 receivers on one side, 1 on the other - The notation indicates distribution across the formation.

23. Sample Answer: Calculate the distance between the quarterback and center at the snap frame. If the QB is within 1-2 yards of the center, they are under center. If the QB is 4-6 yards behind the center, they are in shotgun. Pistol is intermediate (2-4 yards). You can also check if the center and QB are vertically aligned (same y-coordinate indicates true shotgun vs. offset positions).

24. True - The convex hull provides a useful measure of the protected space around the QB.

25. B) Correlation between defender and receiver movements - In man coverage, defenders mirror receiver movements (high correlation); in zone, they stay in areas regardless of receiver movement (low correlation).

26. B) Average distance between all offensive players - Spacing measures how spread out the formation is.

27. B) A skill player moves laterally along the line before the snap - Pre-snap motion typically refers to receivers/backs moving while everyone else is set.

28. True - Hash position affects available field space, influencing optimal route designs (more space to the field side than boundary side).

Section 4: Visualization and Applications

29. C) Update only the elements that change (artist updates) - Using blitting and updating only changed artists is most efficient for animations.

30. A) Red for offense, blue for defense - This is the most common convention, though team colors are also used.

31. Sample Answer: (1) Yard lines (every 5 or 10 yards), (2) End zones with distinct coloring, (3) Hash marks. Additional elements often include: sidelines, yard numbers, team logos, and goal posts.

32. C) Path colored by speed or time - Color-coding provides additional information about when/how the route was run.

33. False - Heat maps are most useful for aggregate analysis, showing tendencies over many plays rather than single-play detail.

34. A) < 100 milliseconds - Broadcast requires near-real-time visualization.

35. B) Distance to nearest defender at catch point - Separation at catch is highly predictive of YAC opportunity, as open space enables additional yards.

Scoring Guide