% Source: http://www.texample.net/tikz/examples/map-projections/ \documentclass[varwidth=true, border=2pt]{standalone} \usepackage{pgfplots} \usepackage{tikz} \usetikzlibrary{calc,fadings,decorations.pathreplacing} \begin{document} %% helper macros \begin{tikzpicture} % CENT \newcommand\pgfmathsinandcos[3]{% \pgfmathsetmacro#1{sin(#3)}% \pgfmathsetmacro#2{cos(#3)}% } \newcommand\LongitudePlane[3][current plane]{% \pgfmathsinandcos\sinEl\cosEl{#2} % elevation \pgfmathsinandcos\sint\cost{#3} % azimuth \tikzset{#1/.estyle={cm={\cost,\sint*\sinEl,0,\cosEl,(0,0)}}} } \newcommand\LatitudePlane[3][current plane]{% \pgfmathsinandcos\sinEl\cosEl{#2} % elevation \pgfmathsinandcos\sint\cost{#3} % latitude \pgfmathsetmacro\yshift{\cosEl*\sint} \tikzset{#1/.estyle={cm={\cost,0,0,\cost*\sinEl,(0,\yshift)}}} % } \newcommand\DrawLongitudeCircle[2][1]{ \LongitudePlane{\angEl}{#2} \tikzset{current plane/.prefix style={scale=#1}} % angle of "visibility" \pgfmathsetmacro\angVis{atan(sin(#2)*cos(\angEl)/sin(\angEl))} % \draw[current plane] (\angVis:1) arc (\angVis:\angVis+180:1); \draw[current plane,dashed] (\angVis-180:1) arc (\angVis-180:\angVis:1); } \newcommand\DrawLatitudeCircle[2][1]{ \LatitudePlane{\angEl}{#2} \tikzset{current plane/.prefix style={scale=#1}} \pgfmathsetmacro\sinVis{sin(#2)/cos(#2)*sin(\angEl)/cos(\angEl)} % angle of "visibility" \pgfmathsetmacro\angVis{asin(min(1,max(\sinVis,-1)))} \draw[current plane] (\angVis:1) arc (\angVis:-\angVis-180:1); \draw[current plane,dashed] (180-\angVis:1) arc (180-\angVis:\angVis:1); } \tikzset{% >=latex, % option for nice arrows inner sep=0pt,% outer sep=2pt,% mark coordinate/.style={inner sep=0pt,outer sep=0pt,minimum size=3pt, fill=black,circle}% } %% some definitions \def\R{2.5} % sphere radius \def\angEl{35} % elevation angle \def\angAz{-105} % azimuth angle \def\angPhi{-40} % longitude of point P \def\angBeta{19} % latitude of point P %% working planes \pgfmathsetmacro\H{\R*cos(\angEl)} % distance to north pole \tikzset{xyplane/.estyle={cm={cos(\angAz),sin(\angAz)*sin(\angEl),-sin(\angAz), cos(\angAz)*sin(\angEl),(0,-\H)}}} \LongitudePlane[xzplane]{\angEl}{\angAz} \LongitudePlane[pzplane]{\angEl}{\angPhi} \LatitudePlane[equator]{\angEl}{0} %% draw xyplane and sphere \draw[xyplane] (-2*\R,-2*\R) rectangle (2.2*\R,2.8*\R); \fill[ball color=white] (0,0) circle (\R); % 3D lighting effect \draw (0,0) circle (\R); %% characteristic points \coordinate (O) at (0,0); \coordinate[mark coordinate] (N) at (0,\H); \coordinate[mark coordinate] (S) at (0,-\H); \path[pzplane] (\angBeta:\R) coordinate[mark coordinate] (P); \path[pzplane] (\R,0) coordinate (PE); \path[xzplane] (\R,0) coordinate (XE); \path (PE) ++(0,-\H) coordinate (Paux); % to aid Phat calculation \coordinate[mark coordinate] (Phat) at (intersection cs: first line={(N)--(P)}, second line={(S)--(Paux)}); %% draw meridians and latitude circles \DrawLatitudeCircle[\R]{0} % equator \DrawLongitudeCircle[\R]{\angAz} % xzplane \DrawLongitudeCircle[\R]{\angAz+90} % yzplane \DrawLongitudeCircle[\R]{\angPhi} % pzplane %% draw xyz coordinate system \draw[xyplane,<->] (1.8*\R,0) node[below] {$x,\xi$} -- (0,0) -- (0,2.4*\R) node[right] {$y$}; \draw[->] (0,-\H) -- (0,1.6*\R) node[above] {$z$}; %% draw lines and put labels \draw[blue,dashed] (P) -- (N) +(0.3ex,0.6ex) node[above left,black] {$\mathbf{N}$}; \draw[blue] (P) -- (Phat) node[above right,black] {$\mathbf{\hat{P}}$}; \path (S) +(0.4ex,-0.4ex) node[below] {$\mathbf{0}$}; \draw (P) node[above right] {$\mathbf{P}$}; \end{tikzpicture} \end{document}