a0poster.cls 中的定位或边距问题

Question

我想用 a0poster.cls 创建一个海报模板（https://www.ctan.org/tex-archive/macros/latex/contrib/a0poster) 并开始设置背景。

为什么定位命令无法正常工作？所有东西都向左和向下移动。类代码中是否有导致这种情况的原因？

\documentclass[a0,portrait]{a0poster}
\usepackage[utf8]{inputenc}
\usepackage{graphicx}
\usepackage{tikz}
\usetikzlibrary{positioning}

\begin{document}
\begin{tikzpicture}[remember picture,overlay]%
  \node[anchor=north west] at (current page.north west) (logo) {\includegraphics[height=4cm]{example-image-a}};
  \node[anchor=north east] at (current page.north east)  {\includegraphics[height=4cm]{example-image-a}};
\node[below= 6cm of current page.north, anchor=north, minimum width=83.1cm, minimum height=1cm, fill=red] {};
\end{tikzpicture}

\end{document}