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Capture and evaluation of airborne laser scanner data 
Johannes Kilian, Norbert Haala and Markus Englich 
Institute of Photogrammetry, Stuttgart University 
KeplerstraBe 11, 70174 Stuttgart 
Phone: 0711-121-3385 
e-mail: Johannes.Kilian@ifp.uni-stuttgart.de 
Commission III/1 
KEY WORDS: calibration, DEM/DTM, filtering, matching, scanner, three-dimensional data acquisition 
ABSTRACT: 
The development of laser sensors for the direct measurement of the terrain surface resulted in airborne systems allowing 
an area covering 3D data capture which are already in commercial use. By the integration of the laser scanner with sensors 
for the absolute orientation of the laser scanner at the time of measurement, like the NAVSTAR Global Positioning System 
(GPS) for the positioning task and an Inertial System (INS) for the orientation task, a powerful sensor system for the 
direct acquisition of 3D terrain data from an aircraft is available. Using scanning laser sensors as the main component 
of the laser sensor system, the points on the the terrain surface can be measured dense and well-distributed. 
The main purpose of the data evaluation is to derive an appropriate representation of the sensed (terrain) surfaces. This 
evaluation of the measured data consists of several single steps. Within this paper the different steps are described and 
results of the data evaluation are presented. 
1 INTRODUCTION 
Applications like the rectification and mono-plotting for re- 
mote sensing data or aerial images require the assembly 
of a Digital Terrain Model (DTM). Usually those DTM 
can be captured automatically by automated stereo image 
matching. Even though this method provides good results 
for open terrain, severe problems can occur for regions, like 
forest areas, wetland and coastal areas and build-up areas. 
To overcome this problems, Airborne laser sensor systems 
have been developed to permit the direct measurement of 
the topographical terrain surface. 
The main fields of application of airborne laser sensor sys- 
tems are expected to be areas, where conventional methods 
of topographical terrain survey (photogrammetry or tachy- 
metry) run into problems or are too slow. 
> forest areas, where tachymetry is too expensive and 
photogrammetry fails due to the problems seeing the 
ground in images in forest areas 
> wetland and coastal areas, where tachymetry fails 
due to the tides and photogrammetry has great prob- 
lems because of the bad block geometry and the low 
texture 
> opencast areas, where results of the surveying are 
needed within a very short period of time 
> urban areas, where image matching techniques suffer 
from problems due to occlusions and height discon- 
tinuities. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996 
The development of airborne laser sensor systems at the 
Institute of Photogrammetry began in 1988. The main 
goal was the development of a sensor system for the direct 
three dimensional airborne measurement of the topograph- 
ical terrain surface, resulting in a digital terrain model of 
the overflown area. 
2 AIRBORNE LASER SENSOR 
SYSTEMS 
An airborne laser sensor system mainly consists of two 
main sensor groups: on the one hand a laser rangefinder, 
which measures the distance from the aircraft to the ter- 
rain surface and on the other hand sensors for the absolute 
orientation of the laser rangefinder at the time of measure- 
ment. 
2.1 SCANNING LASER RANGEFINDERS 
The central component of the airborne laser sensor system 
is a laser sensor, which allows the direct measurement of 
the distance from the aircraft to the topographical terrain 
surface. In the beginning of the development a profiling 
laser sensor was used due to the lack of other laser sensors 
[Lindenberger 1993]. With those sensors the terrain surface 
had to be captured by a lot of parallel profiles. This resul- 
ted in a large effort of time and in high demands on the ac- 
curacy of flight navigation. Nevertheless the high perform- 
ance of airborne laser sensor systems for the direct meas- 
urement of the topographical terrain surface -especially 
in forest areas- could be shown with the profiling laser 
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