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MANAGING FULL WAVEFORM LIDAR DATA: 
A CHALLENGING TASK FOR THE FORTHCOMING YEARS 
F. Bretar 3 , A. Chauve a,c , C. Mallet 3 , B. Jutzi b 
3 IGN-Laboratoire MATIS ;4 av. Pasteur, 94165 Saint Mandé, FRANCE 
b FGAN-FOM, Gutleuthausstr. 1, 76275 Ettlingen, GERMANY 
C UMR TETIS Cemagref/Cirad/ENGREF-AgroParisTech, Maison de la Télédétection 
500, rue J.F. Breton, 34093 Montpellier Cedex 5, FRANCE 
Commission I, WG 1/2 
KEY WORDS: Full waveform, LIDAR, Researches, Data management, Format, Literature review. 
ABSTRACT: 
This paper proposes to summarize researches and new advances in full waveform lidar data. After a description of full waveform 
lidar systems, we will review different methodologies developed to process the waveforms (modelling, correlation, stacking). 
Applications on urban and vegetated areas are then presented. The paper ends up with recommendations on future research themes. 
1. INTRODUCTION 
Airborne laser scanning (ALS) is an active remote sensing 
technique providing range measurements between the laser 
scanner and the Earth topography by the time-of-flight between 
the emitted and backscattered laser pulse. Direct georeferencing 
processes turn such distance measurements into 3D point clouds 
with high accuracy. Even for small footprints, there may be 
several objects of different range within the beam corridor of the 
laser pulse that generate individual backscatter returns (echoes). 
Consequently, commercial systems typically measure first and 
last pulse and some are able to record up to six echoes for each 
emitted laser pulse. Due to the 3D structure of natural and 
artificial objects, the shape of the received pulses may be 
extremely complex and most ALS systems only provide the 
coordinates of these scattering objects. 
During the last years, a new generation of airborne laser 
scanners have been developed which are able to record the 
signal of the entire backscattered laser pulse. These so called full 
waveform LiDAR systems give more control to the end user in 
the interpretation process of the physical measurement. Beside 
the range information, additional information about the structure 
of the illuminated surfaces can be determined. It has already 
been shown that full waveform data post-processing shows 
enormous potentialities for improving forest and urban mapping. 
Full waveform systems can bring two important contributions 
and advantages for additional investigations possibilities. First 
the processing of the received signal can be used to recover all 
individual echoes. This enhances the point cloud density with 
regard to multiple echos (particularly on forest area) as well as 
the quality of the extracted features within the laser beam 
corridor. Second by modelling the received waveforms, 
additional features can be extracted from them. This is for 
example the amplitudes (also called intensity) and the pulse 
width derived by the standard deviation of a Gaussian-based 
decomposition of the waveform. These two values provide 
mixed information about the geometry and the reflectance 
properties of the illuminated surface. 
Full waveform data is mostly used for forest research since the 
first experimental devices, with large footprint, were developed 
for this particular purpose. They produce more detailed 
description of vegetation structures. It is then possible to 
estimate, model and infer forest parameters more reliably. 
The potentialities of full waveform data are definitively high and 
the forthcoming years will be particularly important for the 
development of methodologies, applications and softwares 
within the international LiDAR community. However, if the 
management of multiple echos data made appear standard 
format (e.g. LAS) and software solutions, managing full 
waveform LiDAR data in terms of efficiency have not been 
tackled so far. There are three main reasons that could explain 
this observation: firstly, these data just came out commercially, 
secondly, their volume is several times larger than multi-echos 
data and finally, the potentialities of these data have not been 
turned yet into reality with regard to multi-echo data. 
After a brief reminder of the LiDAR systems themselves, we 
propose in the paper to summarize past researches concerning 
full waveform LiDAR processing with special emphasis on 
forest and urban areas. We will then sketch some proposals for a 
full waveform data format and finally we present new research 
directions. 
2. BACKGROUND ON FULL WAVEFORM LIDAR 
SYSTEM 
The physical principle of ALS consists in the emission of short 
laser pulses, with an width of 5-10 ns at full-width-half- 
maximum, from an airborne platform with a high temporal 
repetition rate of up to 200kHz. They provide a high point 
density and an accurate altimétrie description within the 
diffraction cone. The two way runtime to the Earth surface and 
back to the sensor is measured. Then the range between the 
LiDAR system to the illuminated surface is recorded (Baltsavias, 
1999). The emitted electromagnetic wave interacts with the 
objects surface depending on its wavelength: first with 
atmospheric components like particles refraction, absorption or 
scattering, known to have negligible influence if rain is excluded. 
The main influences on the laser light come from artificial or 
natural objects belonging to the illuminated surface. For ALS 
systems, near infra-red sensors are used (typical wavelengths 
from 0.8 to 1.55pm). Pulse repetition rate depends on the 
acquisition mode and on the flying altitude. Pulse release is done