<p>My assumption was correct: <strong>the ground truth bounding box is aligned with an anchor box such that they share the same center</strong></p>

<p>In other words, only the widths and heights are used to calculate the ground truth IOU.</p>

CC BY-SA 4.0
2018-05-25T04:11:15.277Z
2018-05-25T04:11:15.277Z
nivter
<p>I know how IOU works during detection. However, while preparing targets from ground-truth for training, how is the IOU between a given object and all anchor boxes calculated?</p>
<p><strong>Is the ground truth bounding box aligned with an anchor box such that they share the same center? (width/2, height/2)</strong></p>
<p>I think this is the case but I want to hear from someone who has better knowledge of how training data is prepared for training in YOLO.</p>

CC BY-SA 4.0
2018-05-22T14:03:13.307Z
Can you perhaps provide a bit more context about the system you are talking about?
Oliver Mason
CC BY-SA 4.0
2018-05-22T14:19:17.413Z
@OliverMason: Here's what I am talking about: https://pjreddie.com/darknet/yolo/

In order to train, I need to prepare the training data. One of the fields is 'objectiveness factor' which is defined as IOU between the actual bounding box and best-fitting anchor box. My question is: how are these two boxes aligned?
nivter
<computer-vision><yolo><bounding-box><jaccard-similarity>
How are IOUs for ground truth boxes in YOLO calculated?
nivter
# How are IOUs for ground truth boxes in YOLO calculated?

(Asked by: username_0 on 2018-05-22)

I know how IOU works during detection. However, while preparing targets from ground-truth for training, how is the IOU between a given object and all anchor boxes calculated?

**Is the ground truth bounding box aligned with an anchor box such that they share the same center? (width/2, height/2)**

I think this is the case but I want to hear from someone who has better knowledge of how training data is prepared for training in YOLO.

**Tags:** computer-vision, yolo, bounding-box, jaccard-similarity

> **Comments:**
> **username_1**: Can you perhaps provide a bit more context about the system you are talking about?  
> **username_0**: @OliverMason: Here's what I am talking about: https://pjreddie.com/darknet/yolo/  In order to train, I need to prepare the training data. One of the fields is 'objectiveness factor' which is defined as IOU between the actual bounding box and best-fitting anchor box. My question is: how are these two boxes aligned?  

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## 1 answers

### Answer by username_0 on 2018-05-25. Score: 2 | Accepted answer

My assumption was correct: **the ground truth bounding box is aligned with an anchor box such that they share the same center**

In other words, only the widths and heights are used to calculate the ground truth IOU.


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