\documentclass[10pt]{article}

\usepackage{fullpage}
\usepackage{setspace}
\usepackage{parskip}
\usepackage{titlesec}
\usepackage[section]{placeins}
\usepackage{xcolor}
\usepackage{breakcites}
\usepackage{lineno}
\usepackage{hyphenat}





\PassOptionsToPackage{hyphens}{url}
\usepackage[colorlinks = true,
            linkcolor = blue,
            urlcolor  = blue,
            citecolor = blue,
            anchorcolor = blue]{hyperref}
\usepackage{etoolbox}
\makeatletter
\patchcmd\@combinedblfloats{\box\@outputbox}{\unvbox\@outputbox}{}{%
  \errmessage{\noexpand\@combinedblfloats could not be patched}%
}%
\makeatother


\usepackage{natbib}




\renewenvironment{abstract}
  {{\bfseries\noindent{\abstractname}\par\nobreak}\footnotesize}
  {\bigskip}

\titlespacing{\section}{0pt}{*3}{*1}
\titlespacing{\subsection}{0pt}{*2}{*0.5}
\titlespacing{\subsubsection}{0pt}{*1.5}{0pt}


\usepackage{authblk}


\usepackage{graphicx}
\usepackage[space]{grffile}
\usepackage{latexsym}
\usepackage{textcomp}
\usepackage{longtable}
\usepackage{tabulary}
\usepackage{booktabs,array,multirow}
\usepackage{amsfonts,amsmath,amssymb}
\providecommand\citet{\cite}
\providecommand\citep{\cite}
\providecommand\citealt{\cite}
% You can conditionalize code for latexml or normal latex using this.
\newif\iflatexml\latexmlfalse
\providecommand{\tightlist}{\setlength{\itemsep}{0pt}\setlength{\parskip}{0pt}}%

\AtBeginDocument{\DeclareGraphicsExtensions{.pdf,.PDF,.eps,.EPS,.png,.PNG,.tif,.TIF,.jpg,.JPG,.jpeg,.JPEG}}

\usepackage[utf8]{inputenc}
\usepackage[english]{babel}



\usepackage{float}








\begin{document}

\title{Assessment of ICESat-2 ATL08 Canopy Height Estimates for Tropical
Forests in the Americas}



\author[1]{Juan Fernandez-Diaz}%
\author[1]{Mariya Velikova}%
\author[1]{Craig Glennie}%
\affil[1]{University of Houston}%


\vspace{-1em}



  
  \date{May 21, 2024}


\begingroup
\let\center\flushleft
\let\endcenter\endflushleft
\maketitle
\endgroup





\selectlanguage{english}
\begin{abstract}
A secondary mission objective of NASA's Ice, Cloud and Land Elevation
Satellite-2 (ICESat-2) is to derive vegetation heights that can be used
to refine estimates of above-ground biomass at a global scale {[}1{]} \&
{[}2{]}. In this work we assess the accuracy of ICESat-2 derived canopy
height (CH) retrieval in dense, late-succession, tropical forests in
Mexico, Belize, Guatemala, Honduras, Costa Rica and Brazil. Over 28,000
ICESat-2 ATL-08 canopy height estimates (CHe) are compared against
equivalent metrics derived from spatially coincident linear-mode high
density airborne lidar (HDL) data obtained over a variety of forests
exhibiting different structural characteristics and underlying terrain
conditions. Our preliminary results indicate that in these high closure
forests the ATL08 canopy height estimates (CHe) differ to the airborne
lidar canopy heights (CHr) over a very wide range. The 5 to 95
percentile errors range between an underestimation of negative 26 m to
an overestimation of 27 m; with an interquartile range (IQR) between -14
to 0.25 m. When the samples are stratified using the (CHr) into 5 meter
classes (5-10, 10-15, \ldots{}, 40-45 m), the IQR of the canopy heigh
estimation errors grows exponentially in relation to the CHr
(1.25e\^{}0.057 ; R2=0.97), while the median for each class decreases
linearly at a rate of -0.174m/m (R2 = 0.88). When the ATL08 CHe are
normalized to the reference CH the median of the errors exhibit a mostly
uniform behavior around an underestimation level of 16.4\% . By
analyzing the behavior of other ATL08 parameters such as the terrain
elevation and top of canopy elevations (both absolute elevations above
the ellipsoid) as a function of the CHr, it is apparent that the gradual
underestimation of the vegetation height is due to the inability of the
ICESat-2 sensor and algorithms to accurately detect the terrain under
these dense late-succession tropical forests.%
\end{abstract}%



\sloppy




\selectlanguage{english}
\FloatBarrier
\end{document}

