Overfull \hbox warning in tabular

Question

I have the following table:

\documentclass[border=3mm]{standalone}
    \usepackage{graphicx}
    \usepackage{booktabs,multirow}
    \usepackage{siunitx}
    \usepackage{stackengine}

\begin{document}
\begin{table}[h!]
\begin{center}
\resizebox{\textwidth}{!} {
\begin{tabular}{cc*{2}{S[table-format=-1.3]}
                       S[table-format= 1.3]
                       S
                       S[table-format=-1.3]
                       S[table-format= 3.3]
                       S[table-format= 1.3]}
\toprule
& {\stackon{}{$\mathbf{T^{x\vphantom{y}}_{EO}}$}} 
& {\stackon{[m]}{$\mathbf{T^{x\vphantom{y}}_{EO}}$}}
& {\stackon{[m]}{$\mathbf{T^y_{EO}}$}}
& {\stackon{[m]}{$\mathbf{T^{z\vphantom{y}}_{EO}}$}}
& {\stackon{[deg]}{$\mathbf{R^{x\vphantom{y}}_{EO}}$}}
& {\stackon{[deg]}{$\mathbf{R^y_{EO}}$}}
& {\stackon{[deg]}{$\mathbf{R^{z\vphantom{y}}_{EO}}$}}
& {\stackon{[px]}{\textbf{RMS}\vphantom{y}}} \\
    \midrule
\multirow{4}{*}{\rotatebox[origin=c]{90}{P\textit{n}P-LM}}
    & A & 2.748  & -0.135 & 2.175 & 119.232 & 1.368  & -76.261 & 0.240\\ 
    & B & 2.690  & 0.768  & 2.128 & 124.905 & -1.972 & -91.559 & 0.247\\
    & C & -1.576 & 1.139  & 2.146 & 120.264 & 1.428  & 98.205  & 0.255\\
    & D & -1.575 & -0.122 & 2.165 & 119.634 & -0.818 & 85.313  & 0.231\\
    \midrule
\multirow{4}{*}{\rotatebox[origin=c]{90}{EP\textit{n}P}}
    & A & 2.722  & -0.161 & 2.345 & 121.639 & 1.828  & -75.974 & 0.463\\
    & B & 2.649  & 0.729  & 2.259 & 127.082 & -0.881 & -91.444 & 0.432\\
    & C & -1.565 & 1.148  & 2.246 & 121.639 & 1.250  & 98.377  & 0.389\\
    & D & -1.547 & -0.077 & 2.238 & 120.951 & 0.199  & 85.428  & 0.372\\
    \bottomrule
\end{tabular}
}
\end{center}
\caption{Exterior orientation parameters and corresponding RMS error for all Kinect sensors defined within the chessboard coordinate system.}
\label{tab:rigidParams}
\end{table}
\end{document}

Although it is placed within the width of the text it gives me an overfull warning. I would like to understand why.

Answer 1

The overfull boxes come from the minus signs in the penultimate column. I detected this by adding \showoutput to the original file (with article class rather than standalone, as the latter gave a compilation error). You have just missed the minus in your format specification for the column; it should be

 S[table-format=-3.3]

rather than S[table-format= 3.3].

\documentclass{article}

\usepackage{graphicx}
\usepackage{booktabs,multirow}
\usepackage{siunitx}
\usepackage{stackengine}

\begin{document}

\begin{table}[h!]
\begin{center}
\resizebox{\textwidth}{!} {
\begin{tabular}{cc*{2}{S[table-format=-1.3]}
                       S[table-format= 1.3]
                       S
                       S[table-format=-1.3]
                       S[table-format=-3.3]
                       S[table-format=1.3]}
\toprule
& {\stackon{}{$\mathbf{T^{x\vphantom{y}}_{EO}}$}} 
& {\stackon{[m]}{$\mathbf{T^{x\vphantom{y}}_{EO}}$}}
& {\stackon{[m]}{$\mathbf{T^y_{EO}}$}}
& {\stackon{[m]}{$\mathbf{T^{z\vphantom{y}}_{EO}}$}}
& {\stackon{[deg]}{$\mathbf{R^{x\vphantom{y}}_{EO}}$}}
& {\stackon{[deg]}{$\mathbf{R^y_{EO}}$}}
& {\stackon{[deg]}{$\mathbf{R^{z\vphantom{y}}_{EO}}$}}
& {\stackon{[px]}{\textbf{RMS}\vphantom{y}}} \\
    \midrule
\multirow{4}{*}{\rotatebox[origin=c]{90}{P\textit{n}P-LM}}
    & A & 2.748  & -0.135 & 2.175 & 119.232 & 1.368  & -76.261 & 0.240\\ 
    & B & 2.690  & 0.768  & 2.128 & 124.905 & -1.972 & -91.559 & 0.247\\
    & C & -1.576 & 1.139  & 2.146 & 120.264 & 1.428  & 98.205  & 0.255\\
    & D & -1.575 & -0.122 & 2.165 & 119.634 & -0.818 & 85.313  & 0.231\\
    \midrule
\multirow{4}{*}{\rotatebox[origin=c]{90}{EP\textit{n}P}}
    & A & 2.722  & -0.161 & 2.345 & 121.639 & 1.828  & -75.974 & 0.463\\
    & B & 2.649  & 0.729  & 2.259 & 127.082 & -0.881 & -91.444 & 0.432\\
    & C & -1.565 & 1.148  & 2.246 & 121.639 & 1.250  & 98.377  & 0.389\\
    & D & -1.547 & -0.077 & 2.238 & 120.951 & 0.199  & 85.428  & 0.372\\
    \bottomrule
\end{tabular}
}
\end{center}
\caption{Exterior orientation parameters and corresponding RMS error for all Kinect sensors defined within the chessboard coordinate system.}
\label{tab:rigidParams}
\end{table}
\end{document}