3D surface in pgfplots with given data [closed]

Question

I am trying to make a 3D surface in pgfplots with input data. I am not able to get the expected graph. I would highly appreciate if you could point out to me what I am missing.

\documentclass{standalone}
\usepackage{pgfplots}
\usepackage{filecontents}


\begin{filecontents*}{mydata.dat}
x         y       z
 -1 -1  597.00
  1 -1  649.00
 -1 -1  597.00
  1 -1  649.00
 -1  1 1056.75
  1  1  801.50
 -1  1 1056.75
  1  1  801.50
 -1 -1  597.00
  1 -1  649.00
 -1 -1  597.00
  1 -1  649.00
 -1  1 1056.75
  1  1  801.50
 -1  1 1056.75
  1  1  801.50
\end{filecontents*}

\begin{document}

\begin{tikzpicture}
    \begin{axis}[]
       \addplot3[surf,  mesh] table{mydata.dat};
    \end{axis}
\end{tikzpicture}

\end{document}