How to calculate the confidence score of a keypoint estimation from a heatmap

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I have tried to build the Convolutional Pose Machines model from this paper here (https://arxiv.org/pdf/1602.00134.pdf). The model works fine and outputs 15 heatmaps (one per keypoint + 1 for background). From these heatmaps I can calculate the keypoint positions (simply the max value in the heatmap).

My question is: Is this maximum value in the heatmap also equal to the confidence score of the model that the keypoint is in the image?

Maybe this is a dumb question but in the paper the authors don't mention how they calculate the confidence score or how they handle non-visible keypoints.

pose-estimation
1 Answers

Best way to answer, I believe, is to dig into the actual code of popular pose estimation models using convolutional approach, to see how this is done in practice.

The Google TensorFlow PoseNet model should be a good example.

What they do in their (open source) code, here (check out the predict method), is to apply a 2D sigmoid activation function to the heatmaps, for each keypoint of the pose.

So, to answer your question, I would say that the maximum value in the heatmap is not directly equal to the confidence score - the output of the sigmoid function is (proper score from 0 to 1)

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