ISPRS Commission III, Vol.34, Part 3A ,,Photogrammetric Computer Vision“, Graz, 2002 
  
TRIANGULATION OF LH SYSTEMS" ADS40 IMAGERY USING ORIMA GPS/IMU 
L. Hinsken? , S. Miller, U. Tempelmann ^, R. Uebbing 5 S. Walker? 
* Program Author of ORIMA, St. Verena-Weg 2, D-78465 Konstanz, Germany — Ludger. Hinsken@surf24.de 
® Leica Geosystems, GIS and Mapping Division, 10840 Thornmint Road, Suite 100, San Diego, CA 92127 USA — 
scott. miller@gis.leica-geosystems.com, robert.uebbing@gis.leica-geosystems.com, stewart. walker@gis.leica-geosystems.com 
* Leica Geosystems, GIS and Mapping Division, CH-9435 Heerbrugg, Switzerland — 
udo.tempelmann@gis.leica-geosystems.com 
Commission III, WG III/1 
KEY WORDS: Sensor, Digital, Three-Line, Aerial, Mathematics, Bundle, Triangulation, Orientation, Calibration, Adjustment, 
Software, Technology, Scene, GPS, ADS40, Orientation Fixes 
ABSTRACT: 
The paper describes the mathematical model used for the triangulation of the ADS40. The ADS40 Airborne Digital Sensor is LH 
Systems’ multi-line scanner (Roser, 2000; Sandau, 2000). It is based on the push broom principle and therefore requires more 
complex mathematical modelling than the collinearity equations used in classical bundle triangulation. Particularly significant is the 
use of high precision GPS and Inertial Measuring Unit (IMU) technologies, which constrain the bundle adjustment process. 
KURZFASSUNG: 
Der Artikel stellt das mathematische Modell vor, welches bei der Triangulation von ADS40 Aufnahmen benutzt wird. Der ADS40 
Airborne Digital Sensor ist LH Systems’ Multi-Zeilen Scanner (Roser, 2000; Sandau, 2000). Er basiert auf dem Push Broom Prinzip 
und erfordert daher ein komplexeres mathematisches Modell als es durch die klassische Kollinearitätsgleichung der 
Bündelausgleichung bekannt ist. Von spezieller Bedeutung ist die Benutzung von hochgenauen GPS Positions- und Inertial 
Winkelmessungen, welche als gewichtete Beobachtungen in die kombinierte Ausgleichung einfließen. 
1. INTRODUCTION 
ORIMA, LH Systems’ orientation management software, 
manages all aspects for triangulation on analytical plotters and 
digital workstations. It has been extended to handle the special 
requirements for the new multi-line sensor ADS40. The ADS40 
is a push broom scanner and therefore the triangulation software 
must use another sensor model than that used for frame 
photography. The whole workflow of the triangulation process 
using the ADS40 is fairly different compared to the 
conventional workflow for frame photography. Triangulation is 
only one step in the total data processing chain from the sensor 
to the final product: all processing steps are described by 
Tempelmann (2000). The overall process includes GPS/IMU 
data processing and image rectification. These important steps 
have to be performed prior to the triangulation. 
1.1 Motivation for Triangulation with ADS40 
The ADS40 is equipped with a GPS/IMU system. This is used 
to record the motion of the sensor during the flight. The 
specifications of this system are such that the resultant 
orientation is suited for certain types of products, but may not 
meet accuracy requirements for more accurate mapping 
applications. To obtain the highest possible accuracy plus 
additional reliability a triangulation is required. The 
triangulation is further used to calibrate certain system 
parameters and in combination with control points leads to the 
best fit to the ground system. 
1.2 Essential Pre-Processing before the Triangulation 
The GPS/IMU data is first processed in a way that six 
orientation parameters for each sensor line are given in a local 
A- 156 
Cartesian co-ordinate system. The CORE module of the 
SOCET SET®' digital workstation software takes care of 
transformations between the local Cartesian system and the 
final mapping system. To be able to use SOCET SET’s® 
automatic tie point matching software, the original scenes, 
which are denoted as Level 0, are rectified to Level 1. This 
rectification is based on the orientation values that are obtained 
by the GPS/IMU post processing software. The distortion in the 
scenes of Level 0, caused by the motion of the sensor, are 
removed by this rectification and the scenes of Level 1 can be 
viewed stereoscopically. 
Although the scenes used for triangulation are rectified to Level 
| the tie points measured are referred directly to the original 
Level 0 image. The orientation parameters to be updated by the 
bundle adjustment will also refer to the orientation of the sensor 
lines at Level 0. The SOCET SET® ADS40 sensor model is 
designed in a way that the transformations between Level 0 and 
Level 1 are performed in real-time. 
1.3 Post-Processing after the Triangulation 
Once the orientation parameters are updated by the bundle 
adjustment, the user can proceed with subsequent data 
extraction tasks using the Level 1 rectified data. This can 
include feature extraction, DTM extraction, orthophoto 
production, etc. Optionally, the user can create orthorectified 
imagery from the raw level 0 imagery. Precisely orthorectified 
images are referred to as Level 2 images. 
  
! SOCET SET is a registered trademark of BAE Systems 
Mission Solutions Inc.