How do I find the groundtruth of an image?

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I'm trying to evaluate the accuracy of my detection results. May I know how do I label the groundtruth and do I have to manually label the object? If so, how do I do it?

Accepted Answer

Dima Lisin
Dima Lisin on 8 Dec 2015
Try the Training Image Labeler app in the Computer Vision System Toolbox.
Dima Lisin
Dima Lisin on 10 Dec 2015
"Hand-labeled bounding box" means you draw it by hand, and somehow extract its coordinates. This is exactly what trainingImageLabeler lets you do, and you said you were using it already.
When you labeled your training images, you have created ground truth. You can simply use some of those images for testing.
Walter Roberson
Walter Roberson on 10 Dec 2015
Semantically, ground truth is what is "really" there, potentially more accurate than your labeling of it from a visual image. You might need to use multiple modalities to find ground truth, such as combining x-ray with MRI and contrast-enhanced florescence. The whole point can be to see how well you can match reality by using a single or inexpensive or faster method and good algorithms.

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More Answers (1)

Walter Roberson
Walter Roberson on 8 Dec 2015
Someone has to manually label the ground truth. That might occur by using some kind of program to do the "obvious" parts of it, followed by a human touching it up.
Ground truth labeling is, by definition, only applied to labeling that is absolutely completely correct in every location, known to be correct because of some external information. For example, a picture of a boundary might have been labeled after electron microscope examination of the surface in order to determine atom by atom where one substance stopped and another started. For a picture of a forest, you might have had a team of scientists go tree by tree extracting DNA samples and then having specialists in each genus determining exactly which species (or varietal) occurred.
If there is any chance of error in a groundtruth labeling then the labeling is not groundtruth -- but it might be Gold Standard (determined by an experienced expert) instead. Groundtruth is "we know for certain that this is right".
Leonard Yeo
Leonard Yeo on 8 Dec 2015
Edited: Leonard Yeo on 8 Dec 2015
" Someone has to manually label the ground truth." do you mean that I have to manually draw a bounding box around the object using any kind of program (i.e. paint or photoshop)?
Walter Roberson
Walter Roberson on 8 Dec 2015
No, but that is one option. Bounding boxes get clumsy for anything that is curved or irregular shaped.

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