Constant caption vertical position including on chapter pages

Question

I would like captions (which will always be above the figure, table, etc) to be placed in the same vertical position on the page. I know I can do

\makeatletter
\setlength{\@fptop}{0.16\textheight minus 0.160\textheight}
\makeatother

which makes the vertical position 16% of the way down the text height. However, I am using twocolumn report document and when a figure is placed early in a chapter, the figure appears lower. I understand that this is because it is 16% of the textheight + chapter title area height.

How can I make such figures appear on the same vertical position as other figures?

I have a MWE which achieves the effect below, but requires me to manually determine the correct height of the minipage, and to use a separate environment from figure for figures appearing on the chapter page. Is there another way? Alternatively, if this way is the best, is there a way to refer to the "chapter title area height" so that if I change the way chapters are displayed the same effect is achieved?

(If a figure is too large on a `normal' page, I am not worried if it moves up.)

\documentclass[a4paper,twocolumn,10pt]{scrreprt}
\usepackage[twocolumn,landscape,top=1cm]{geometry}

\usepackage{lipsum}
\usepackage{graphicx}
\usepackage{placeins}

\renewcommand{\floatpagefraction}{0.1}

\makeatletter
\setlength{\@fptop}{0.16\textheight minus 0.1650\textheight}
\makeatother

\newenvironment{chapterpagefigure}{
\begin{figure}
\begin{minipage}[t][0.84\textheight]{\linewidth}
}{
\end{minipage}
\end{figure}
}

\usepackage{caption}
\captionsetup{justification=raggedright,singlelinecheck=false,skip=0pt}


\begin{document}
\chapter{A somewhat long chapter title longer than two columns}
\lipsum[1-3]

\begin{chapterpagefigure}
\caption{Figure appearing on chapter page}
\includegraphics[height=5cm]{Example-image}
\end{chapterpagefigure}

\lipsum[1-2] 
\section{Foobarbaz}

\begin{figure}[p]
\caption{Slightly larger figure appearing on normal page}
\includegraphics[height=6cm]{Example-image}
\end{figure}

\lipsum

\lipsum[1-4]

\begin{figure}[p]
\caption{Slightly larger figure appearing on normal page}
\includegraphics[height=6cm]{Example-image}
\end{figure}




\end{document}

Answer 1

On the first page of a chapter, \@colht is less than \textheight. The macro \@tryfcolumn is used to lay the floats out into each column. The change in \@fptop is local to each call.

\documentclass[a4paper,twocolumn,10pt]{scrreprt}
\usepackage[twocolumn,landscape,top=1cm]{geometry}

\usepackage{lipsum}
\usepackage{graphicx}
\usepackage{placeins}

\renewcommand{\floatpagefraction}{0.1}

\makeatletter
\setlength{\@fptop}{0.16\textheight minus 0.1650\textheight}
\let\oldtryfcolumn=\@tryfcolumn
\def\@tryfcolumn{\addtolength{\@fptop}{\dimexpr \@colht-\textheight}%
  \oldtryfcolumn}
\makeatother

\usepackage{caption}
\captionsetup{justification=raggedright,singlelinecheck=false,skip=0pt}


\begin{document}
\chapter{A somewhat long chapter title longer than two columns}
\lipsum[1-3]

\begin{figure}[p]
\caption{Figure appearing on chapter page}
\includegraphics[height=5cm]{Example-image}
\end{figure}

\lipsum[1-2] 
\section{Foobarbaz}

\begin{figure}[p]
\caption{Slightly larger figure appearing on normal page}
\includegraphics[height=6cm]{Example-image}
\end{figure}

\lipsum

\lipsum[1-4]

\begin{figure}[p]
\caption{Slightly larger figure appearing on normal page}
\includegraphics[height=6cm]{Example-image}
\end{figure}

\end{document}