Suppose I have a set of N images and I have already computed the SIFT descriptors of each image. I know would like to compute the matches between the different features. I have heard that a common approach is the Lowe's ratio test but I cannot understand how it works. Can someone explain it to me?
For better understanding the ratio test, you need to read his article. Only by reading the article you will find out your answer. The simple answer is that it is low, which Lowe achieved during his experiments and suggest that for choosing between two similar distance, choose the one which its distance is 0.7 other one.
check the below link: https://www.cs.ubc.ca/~lowe/papers/ijcv04.pdf
来源：https://stackoverflow.com/questions/51197091/how-does-the-lowes-ratio-test-work