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ON IMPROVEMENT OF ACCURACY OF AIRBORNE LASER SCANNER DATA 
USING DIGITAL IMAGES 
Kazuya NAKANO a *, Hirofumi CHIKATSU b * 
a System Development Group, AERO ASAHI CORPORATION, 
3-1-1, Minamidai, Kawagoe, Saitama, 350-1165, Japan - kazuya-nakano@aeroasahi.co.jp 
b Dept, of Civil and Environmental Engineering, Tokyo Denki University, 
Ishizaka, Hatoyama, Saitama, 350-0394, Japan - chikatsu@g.dendai.ac.jp 
Commission I, WG 1/2 
KEYWORDS: LIDAR, Integration, Aerial Photogrammetry, GPS/INS, Bundle Adjustment, Georeferencing 
ABSTRACT: 
Airborne laser scanner is useful system for acquiring point clouds 3D data with real-time, and it came to be generally used in the late 
1990s. Airborne laser scanner have effectiveness in extracting micro topography or ground surface under the trees which are not 
detect by photogrammetry, and many applications such as city modelling, DTM generation, monitoring electrical power lines and 
detection of forest areas were proposed. The most remarkable point of this system, however, is its ability to obtain 3D coordinates of 
huge object points with real-time. Airborne Laser Scanner is basically based on GPS, inertial measurement unit (IMU) and laser 
scanning device (Laser Rangefinder). GPS and IMU provide position and attitude information regarding trajectory of platform, and 
laser scanning device give distance between platform and the object points. Therefore, direct-georeferencing system using 
GPS/IMU comes to be utilized widely in the field of aerial photogrammetry, nevertheless matching among stereo models and 
courses are not adjusted since the direct-georeferencing system are influenced by cycle-slip and satellite placement. This paper 
investigates fundamental studies to improve of accuracy of airborne laser scanner data using digital images. 
1. INTRODUCTION 
Airborne laser scanner came to be generally used for terrain 
measurement from the view point of prominent characteristic 
(Baltsavias, 1999). Airborne laser consists of 2 key 
technologies as spin-off of military technology; one is 
GPS/IMU (i.e. direct-georeferencing), other is laser scanning 
device. Current paradigm shift of platform orientation was 
caused by direct-georeferencing using GPS/IMU nevertheless 
system calibration in GPS/IMU system is the most critical 
factor (Cramer and Stallmann, 2002). 
In order to control quality of aerial photogrammetry using 
GPS/IMU system, Geographical Survey Institute (GSI) 
prescribe establishments of several ground control points and 
practice of aerial triangulation in generating large scale maps 
such as 1/1,000. GSI also prescribe mechanical accuracy such 
as ±30 cm accuracy for GPS by continuous kinematic, and 
rolling and pitching accuracy are 0.013 degrees, heading is 
0.035 degrees for IMU respectively. 
In the meantime, GSI has established 1,224 GPS stations all 
over the country for monitoring of the crustal movement. Then, 
it become possible to utilize these GPS stations for quality 
control of airborne laser scanner data, and GSI prescribe 
mechanical accuracy as same as the aerial photogrammetry so 
that ±25 cm accuracy are achieved in vertically by airborne 
laser scanner. 
On the contrary, take into account that the direct- 
georeferencing system are influenced by cycle-slip and satellite 
placement, some adjustment for the direct-georeferencing 
system in airborne laser scanner should be considered as well as 
establishment of several ground control points and practice of 
aerial triangulation in the aerial photogrammetry using 
GPS/IMU. 
In order to improve the issues such as cycle-slip and satellite 
placement in the direct-georeferencing system, simultaneous 
adjustment combined with aerial photogrammetry and airborne 
laser scanner become possible under consideration of current 
situation that non-metric digital camera is equipped with 
airborne laser scanner system. However, previous interior 
orientation procedure newly comes up as the another issue since 
interior orientation procedure for non-metric digital camera is 
generally performed beforehand using test sheet or test target, 
and the previous interior orientation procedure should be 
removed for ideal direct-georeferencing system. 
With this motive, simultaneous adjustment such as bundle 
adjustment with self-calibration is proposed in this paper so that 
exterior orientation parameters which are obtained from 
GPS/IMU system, 3D objects coordinate which are acquired 
from laser scanner and the interior orientation parameters are 
adjusted simultaneously. Though, the combined orientations in 
block adjustment had been proposed in late 1900’s (Ackermann, 
& et al., 1972, EL-Hakim & Faig, 1981, Chikatsu, & et al., 
1988), it is enormously expected that the proposed adjustment 
will make possible to utilize airborne laser scanner in 
generating large scale map, and efficient aerial photogrammetry 
except the geodetic data such as ground control points and the 
aerial triangulation will be accomplished. 
2. WORKFLOW 
In order to achieve the simultaneous adjustment, brief 
procedures which are investigated in this paper are as follows.