# Matrix Notation: What does A = [R | t] mean?

I am reading about homography in images and such. One thing pops up a lot:

$\mathbf{P} = [\mathbf{R}|\mathbf{t}]$

What does this mean?

Does this mean: If $\mathbf{R} = \begin{bmatrix}a & b\\\ c &d\end{bmatrix}$ and $\mathbf{t} = \begin{bmatrix}x\\\ y\end{bmatrix}$, I get $\mathbf{P} = \begin{bmatrix}a &b &x\\\ c& d& y\end{bmatrix}?$

• Could you mention what book are you looking at? Jul 21, 2011 at 14:37
• Yes, I think you got this right. Think of matrices $\mathbf{R}, \mathbf{S}$ as consisting of their columns. Then $[\mathbf{R}|\mathbf{S}]$ usually means the matrix consisting of the columns of $\mathbf{R}$ then $\mathbf{S}$ (assuming that $\mathbf{R},\mathbf{S}$ have the same number of rows.
– t.b.
Jul 21, 2011 at 14:38
• @J.M. I am looking at Hartley & Zisserman, Multiple View Geometry (2000/2003) Jul 21, 2011 at 14:53
• Yes, if you read through the book carefully, you'll see that it's their notation for a "camera matrix". Jul 21, 2011 at 15:01
• Well, I only have access to the chapter posted on Zisserman's website. Jul 22, 2011 at 8:46