Center two tikzpicture subfloats on a landscape page

Question

I want to center two tikzpictures which are both in a own subfloat on a landscape page. With my example code the begin of the second timeline is shifted. You can see the shift in the picture. I want to have the beginnigs of the two timelines on the same horizontal line.

\documentclass[a4paper,11pt,smallchapters,blue,extramargin,lnum]{article}
\usepackage{lscape}
\usepackage{subfig}
\usepackage{graphicx}
\usepackage{tikz}
\begin{document}

\begin{landscape}
    \vspace*{\fill}
    \begin{figure}[h]
        \begin{center}
            \subfloat[Situation 1 \label{fig:situationen-2.impl-exp3:situation1}] {
                \begin{tikzpicture}
                    % draw horizontal line   
                    \draw (0,0) -- (15,0);

                    % draw vertical lines
                    \foreach \x in {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}
                        \draw (\x cm,3pt) -- (\x cm,-3pt);

                    % draw nodes
                    \draw (0,0) node[below=3pt] {$ 0s $} node[above=15pt] {Raspberry Pi} node[above=1pt] {sendet};
                    \draw (10,0) node[below=3pt] {$ 50s $} node[above=12pt] {Beginn} node[above=1pt] {Zustandswechsel};
                    \draw (15,0) node[below=3pt] {$ 150s $} node[above=3pt] {Ende};  
                \end{tikzpicture}
            } 
            \newline
            \subfloat[Situation 2 \label{fig:situationen-2.impl-exp3:situation2}] {
                \begin{tikzpicture}
                    % draw horizontal line   
                    \draw (0,0) -- (15,0);

                    % draw vertical lines
                    \foreach \x in {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}
                        \draw (\x cm,3pt) -- (\x cm,-3pt);

                    % draw nodes
                    \draw (0,0) node[below=3pt] {$ 0s $} node[above=15pt] {Raspberry Pi} node[above=1pt] {sendet};
                    \draw (5,0) node[below=3pt] {$ 50s $} node[above=12pt] {Beginn} node[above=1pt] {Zustandswechsel};
                    \draw (10,0) node[below=3pt] {$ 100s $} node[above=12pt] {Senderate} node[above=1pt] {kleiner};
                    \draw (15,0) node[below=3pt] {$ 150s $} node[above=3pt] {Ende};  
                \end{tikzpicture}
            } 
            \caption{Untersuchte Situationen in Experiment 3 der 2.Implementierung} \label{fig:situationen-2.impl-exp2}
        \end{center}
    \end{figure}
    \vspace*{\fill}
\end{landscape}

\end{document}

Answer 1

The problem is caused by the combination of centred text and the forced line break from \newline. You can avoid this by simply leaving an empty line to start a new paragraph:

\documentclass[a4paper,11pt,smallchapters,blue,extramargin,lnum]{article}
\usepackage{lscape}
\usepackage{subfig}
\usepackage{graphicx}
\usepackage{tikz}
\begin{document}

\begin{landscape}
    \vspace*{\fill}
    \begin{figure}[h]
        \centering
%        \begin{center}
            \subfloat[Situation 1 \label{fig:situationen-2.impl-exp3:situation1}] {
                \begin{tikzpicture}
                    % draw horizontal line   
                    \draw (0,0) -- (15,0);

                    % draw vertical lines
                    \foreach \x in {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}
                        \draw (\x cm,3pt) -- (\x cm,-3pt);

                    % draw nodes
                    \draw (0,0) node[below=3pt] {$ 0s $} node[above=15pt] {Raspberry Pi} node[above=1pt] {sendet};
                    \draw (10,0) node[below=3pt] {$ 50s $} node[above=12pt] {Beginn} node[above=1pt] {Zustandswechsel};
                    \draw (15,0) node[below=3pt] {$ 150s $} node[above=3pt] {Ende};  
                \end{tikzpicture}
            } 


            \subfloat[Situation 2 \label{fig:situationen-2.impl-exp3:situation2}] {
                \begin{tikzpicture}
                    % draw horizontal line   
                    \draw (0,0) -- (15,0);

                    % draw vertical lines
                    \foreach \x in {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}
                        \draw (\x cm,3pt) -- (\x cm,-3pt);

                    % draw nodes
                    \draw (0,0) node[below=3pt] {$ 0s $} node[above=15pt] {Raspberry Pi} node[above=1pt] {sendet};
                    \draw (5,0) node[below=3pt] {$ 50s $} node[above=12pt] {Beginn} node[above=1pt] {Zustandswechsel};
                    \draw (10,0) node[below=3pt] {$ 100s $} node[above=12pt] {Senderate} node[above=1pt] {kleiner};
                    \draw (15,0) node[below=3pt] {$ 150s $} node[above=3pt] {Ende};  
                \end{tikzpicture}
            } 
            \caption{Untersuchte Situationen in Experiment 3 der 2.Implementierung} \label{fig:situationen-2.impl-exp2}
%        \end{center}
    \end{figure}
    \vspace*{\fill}
\end{landscape}

\end{document}

(I'm using \centering instead of the center environment to avoid additional vertical spacing, but for your use case that's not really important)