\documentclass{article}
\usepackage{tikz}
\usepackage[graphics, active, tightpage]{preview}
\PreviewEnvironment{tikzpicture}
\usepackage{ngerman}

%!tikz preamble begin
\newcommand\width{2.5}
\newcommand\colZ{-3*\width}
\newcommand\colA{-2*\width}
\newcommand\colB{-1*\width}
\newcommand\colC{0*\width}
\newcommand\colD{1*\width}
\newcommand\colE{2*\width}

\newcommand\height{3.5}
\newcommand\Band[1]{*\height*-1+#1*\height*-1}
\newcommand\Bsm{\Band{-5}}
\newcommand\Bum{\Band{-6}}
\newcommand\Bmm{\Band{-3}}
\newcommand\Bcm{\Band{-2}}
\newcommand\Bdm{\Band{-1}}
\newcommand\Bm{\Band{0}}
\newcommand\Bdam{\Band{1}}
\newcommand\Bhm{\Band{2}}
\newcommand\Bkm{\Band{3}}
\newcommand\Blm{\Band{4}}

\newcommand{\boxn}[2]{
\draw[gray] (\colZ-1,#1) rectangle (\colE+1,#2);
}

\newcommand{\unit}[3]{
\node[unit] (#3) at (#1,#2) {#3};
}

\newcommand{\unitbox}[3]{
\boxn{#1}{#2}
\unit{\colZ}{#1}{#3}
}

\newcommand{\arrow}[3]{
\draw [->, font=\tiny] (#1) -- node{#3} (#2);
}

\newcommand{\arrowcontrolled}[4]{
\draw [->, font=\tiny] (#1) .. controls #4 .. node{#3} (#2);
}
%!tikz preamble end


\begin{document}
\begin{tikzpicture}

\tikzset{unit/.style={rectangle,draw=black!50,fill=white!20},every node/.style={fill=white!20}};

\boxn{0\Bsm}{0\Bmm}
\unitbox{0\Bmm}{0\Bcm}{mm}
\unitbox{0\Bcm}{0\Bdm}{cm}
\unitbox{0\Bdm}{0\Bm}{dm}
\unitbox{0\Bm}{0\Bdam}{m}
\unitbox{0\Bdam}{0\Bhm}{dam}
\unitbox{0\Bhm}{0\Bkm}{hm}
\unitbox{0\Bkm}{0\Blm}{km}

\unit{\colA}{1.405\Bum}{mil}
\unit{\colB}{0.268\Bkm}{nautical mile}

\unit{\colA}{0.882\Bdm}{grade/step}
\unit{\colA}{0.183\Bm}{Roman pace}
\unit{\colA}{0.785\Bm}{rope}
\unit{\colA}{0.484\Bdam}{Ramsden's chain}
\unit{\colA}{0.183\Bkm}{Roman mile}


\unit{\colB}{1.246\Bum}{twip}
\unit{\colB}{2.548\Bum}{point}
\unit{\colB}{0.326\Bmm}{line}
\unit{\colB}{0.627\Bmm}{pica}
\unit{\colB}{0.928\Bmm}{barleycorn}
\unit{\colB}{0.405\Bcm}{inch}
\unit{\colB}{0.007\Bdm}{hand}
\unit{\colB}{0.484\Bdm}{foot}
\unit{\colB}{0.961\Bdm}{yard}
\unit{\colB}{0.262\Bm}{fathom}
\unit{\colB}{0.438\Bdam}{shackle}
\unit{\colB}{0.040\Bhm}{skein}
\unit{\colB}{0.341\Bhm}{cable}

\unit{\colC}{0.280\Bcm}{digit}
\unit{\colC}{0.882\Bcm}{palm}
\unit{\colC}{0.183\Bdm}{shaftment}
\unit{\colC}{0.660\Bdm}{cubit}

\unit{\colD}{0.757\Bcm}{nail}
\unit{\colD}{0.058\Bdm}{finger}
\unit{\colD}{0.359\Bdm}{span}
\unit{\colD}{0.058\Bm}{ell}

\unit{\colE}{0.304\Bdm}{link}
\unit{\colE}{0.701\Bm}{rod}
\unit{\colE}{0.304\Bdam}{chain}
\unit{\colE}{0.304\Bhm}{furlong}
\unit{\colE}{0.207\Bkm}{mile}
\unit{\colE}{0.684\Bkm}{league}

\arrow{mm}{cm}{10}
\arrow{cm}{dm}{10}
\arrow{dm}{m}{10}
\arrow{m}{dam}{10}
\arrow{dam}{hm}{10}
\arrow{hm}{km}{10}
\arrowcontrolled{km}{nautical mile}{1.852}{(0.9*\colZ + 0.1*\colA, 0.4\Bkm)}

\arrow{grade/step}{Roman pace}{2}
\arrow{Roman pace}{rope}{4}
\arrow{rope}{Ramsden's chain}{5}
\arrow{Ramsden's chain}{Roman mile}{50}
\arrowcontrolled{foot}{Roman pace}{5}{(0.6*\colB + 0.4*\colA, 0.9\Bdm)}

\arrow{link}{rod}{25}
\arrow{rod}{chain}{4}
\arrow{chain}{furlong}{10}
\arrow{furlong}{mile}{8}
\arrow{mile}{league}{3}
\arrowcontrolled{cubit}{rod}{11}{(\colC, 0.2\Bm)}
\arrow{fathom}{chain}{11}

\arrowcontrolled{mil}{inch}{1000}{(0.7*\colA + 0.3*\colB, 0\Bcm)}
\arrow{point}{line}{6}
\arrow{twip}{point}{20}
\arrow{line}{pica}{2}
\arrow{pica}{barleycorn}{2}
\arrow{barleycorn}{inch}{3}
\arrow{inch}{hand}{4}
\arrow{hand}{foot}{3}
\arrow{foot}{yard}{3}
\arrow{yard}{fathom}{2}
\arrow{fathom}{shackle}{15}
\arrow{shackle}{skein}{4}
\arrow{skein}{cable}{2}
\arrow{ell}{shackle}{24}
\arrow{cm}{inch}{2.54}
\arrowcontrolled{m}{yard}{0.9144}{(\colA, 0.5\Bdm)}

\arrow{digit}{palm}{4}
\arrow{palm}{shaftment}{2}
\arrow{shaftment}{cubit}{3}

\arrow{inch}{digit}{$\frac{3}{4}$}
\arrow{inch}{palm}{3}
\arrow{shaftment}{foot}{2}
\arrow{cubit}{yard}{2}

\arrow{nail}{finger}{2}
\arrow{finger}{span}{2}
\arrow{span}{ell}{5}

\arrow{digit}{nail}{3}
\arrow{palm}{span}{3}
\arrow{span}{cubit}{2}
\arrow{cubit}{ell}{$\frac{5}{2}$}

\end{tikzpicture}
\end{document}