difference between ASTER and SRTM (i.e., considering

$\mbox{ASTER}_i-\mbox{SRTM}_i$ for all pixels $i$ where the two DEMs

co-occur) is \Sexpr{delta.median} meters, with a mean of

\ref{aster-srtm-bins}). However, while this average offset is broadly

consistent across latitudes and across elevation zones, additional

variation is evident at the pixel level. Again focusing on the

% Figure: Boundary analysis region

%

\begin{figure}[h]

  \centering

<<echo=FALSE,results=hide,fig=TRUE,height=5,width=7>>=

  par(omi=c(0,0,0,0))

  \subfloat[Pixel-wise plot of SRTM vs ASTER for all values in the 150

  latitudinal rows of overlap south of 60\N. Dashed blue line indicates

  the 1:1 diagonal, and the parallel red line is offset lower by the

  Inset histogram shows distribution of differences, excluding absolute

    \includegraphics[width=\linewidth, trim=0 0 0 0.5in, clip=TRUE]{../dem/aster-srtm-scatter.png}

    \label{aster-srtm-scatter}

  }

\end{figure}

%-----------------------------------------------------------------------

\section{Code listings}

%-----------------------------------------------------------------------

\lstinputlisting[language=bash, caption={GDAL commands for assembling

    and resampling SRTM and ASTER tiles into GeoTIFFs for use as inputs

    to the boundary correction routines described in this document.},

text(10, 0.4*max(h$counts), labels=paste("Entire range:\n(",

    min(delta.vals), ", ", max(delta.vals), ")", sep=""), cex=0.6,

    adj=c(0,0))

dev.off()