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### Rank of a Homography (Sample Solution to Assignment 4)

Verfasst: **14. Aug 2013 12:37**

von **lustiz**

Hi there, just want to mention something odd about the sample solution to assignment 4. That is, when the homography has been computed, a rank of 2 is enforced. To my knowledge that is pretty conterproductive as a homography with a rank of 2 is no one-to-one mapping anymore. Furthermore, if you enforce a rank of 2, every point of the first image gets projected to a line of the second image. Would be great if you can give a hint about this because I always assumed a proper homography has a rank of 3.

Thanks in advance!

### Re: Rank of a Homography (Sample Solution to Assignment 4)

Verfasst: **14. Aug 2013 15:26**

von **psheldr**

Is it maybe the fundamental matrix that has a rank of 2 enforced and not of a 2d homography?

### Re: Rank of a Homography (Sample Solution to Assignment 4)

Verfasst: **14. Aug 2013 16:00**

von **lustiz**

That was basically my point, yes.

### Re: Rank of a Homography (Sample Solution to Assignment 4)

Verfasst: **14. Aug 2013 16:51**

von **psheldr**

Are you referring to the sample solution to problem 2 of assignment 4 or to problem 3? The rank of a 2d homography is usually 3.

### Re: Rank of a Homography (Sample Solution to Assignment 4)

Verfasst: **14. Aug 2013 17:18**

von **lustiz**

Problem 3.