Understanding IoU

Imagine a scenario where we came up with a prediction of a bounding box for an object. How do we measure the accuracy of our prediction? The concept IoU comes in handy in such a scenario.

The word intersection within the term intersection over union refers to measuring how much the predicted and actual bounding boxes overlap, while union refers to measuring the overall space possible for overlap. IoU is the ratio of the overlapping region between the two bounding boxes over the combined region of both bounding boxes.

This can be represented in a diagram, as follows:

Figure 7.6: Visualizing IoU

In the preceding diagram of two bounding boxes (rectangles), let’s consider the left bounding box as the ground truth and the right bounding box as the predicted location of the object. IoU as a metric is the ratio of the overlapping region over the combined region between the two bounding boxes. In the following diagram, you can observe the variation...