# A Comprehensive Review of Computer Vision in Sports:
## 4 Literature Review
### Hockey/Ice Hockey  
Hockey, also known as Field hockey, is an outdoor game played between two teams of 11 players each. These players use sticks that are curved at the striking end to hit a small and hard ball into their opponent's goal post. So, detecting [176] and tracking the \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & & & \\ \hline \hline
**Ref.** & **Problem Statement** & **Proposed Methodology** & **Precision and Performance Characteristics** & **Limitations and Remarks** \\ \hline
[173] & Group activity & & & The model achieved an accuracy of 93.9\%. & The model fails to track the players if the video is taken from a dynamic camera. Temporal action localization can improve the accuracy of tracking the players in severe occlusion conditions. \\ \hline
[174] & Recognizing and & & & \\ classifying player’s behavior. & SVM & The achieved recognition rate 98\% for 349 correct samples. & - \\ \hline
[167] & Classification of & & & The model achieves better classification results as prediction accuracies range from 37\% for forecasting the attack and direction to 60\% for the prediction of success. & By employing a state-of-the-art method and training on a proper dataset that has continuous positional data, it is possible to predict tactics behavior and set/match outcomes. \\ \hline
[175] & Motion estimation for & Machine Vision and & & \\ volleyball & Classical particle filter. & Tracking accuracy is 89\% & Replacing methods with deep learning algorithms gives better results. \\ \hline
[168] & Assessing the use of & & & \\ Inertial Measurement & Units in the & & & \\ recognition of & & & & \\ different volleyball & & & & \\ actions. & & & & \\ \hline
[59] & Predicting the ball & & & \\ trajectory in a & & & The proposed method predicts & In the case of predicting the 3D body \\ volleyball game by & & & 0.3 s in advance of the trajectory & position data, the method records a large error. This can be overcome by training \\ observing the the & & & of the volleyball based on the motion of the setter player. & properly annotated large data on \\  & & & & state-of-art-methods. \\ \hline
[164] & Activity recognition in & & & The approach achieved a classification accuracy of 83.2\%, which is superior compared with other classification algorithms. & Instead of using wearable devices, computer vision architectures can be used to classify the activities of the \\ \hline
[170] & Volleyball skills and & & & Evaluated in terms of Average & \\ tactics analysis & & & Relative Error for 10 samples & - \\  & & & and achieved 0.69\%. & The performance of architecture is poor \\ \hline
[165] & Group activity & & Group activity recognition of accuracy of the the proposed & because of the lack of hierarchical considerations of the individual and \\  & & & model in volleyball is 51.1\%. & group activity dataset. \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Studies in volleyball. player/hockey ball, recognizing the actions of the player [177, 178, 179], estimating the pose of the player [180], classifying and tracking the players of the same team or different teams [181], referee gesture analysis [182, 183] and hockey ball trajectory estimation are the major aspects of hockey sport. Ice hockey is another similar game to field hockey, with two teams with six players each, wearing skates and competing on an ice rink. All players aim to propel a vulcanized rubber disk, the puck, past a goal line and into a net guarded by a goalender. Ice hockey is gaining huge popularity on international platforms due to its speed and frequent physical contact. So, detecting/tracking the player [184, 185, 186], estimating the pose of the player [187], classifying and tracking with different identification the players of the same team or different teams, tracking the ice hockey puck [188], and classification of puck possession events [189] are the major aspects of the ice hockey sport. Table 7 summarizes various proposed methodologies to resolve various challenging tasks in hockey/ice hockey with their limitations.