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DISCUSSION OF GPS SUPPORTED AUTOMATIC TRIANGULATION BASE 
ON THE DMC IMAGES 
Tang Li, Liu Jibao, Li Jun 
Xi’an ARSC Information Industry Limited, Surveying and Mapping Engineering Branch 
No.3 JianXi Street, 710054 - tangliarsc@sina.com 
WG IV/l-Spatial Data Infrastructure 
KEY WORDS: Photogrammetry, ISAT, GPSMNS, IMU, DMC 
ABSTRACT: 
With the development of modem aerophotogrammetry technology, GPSMNS(IMU) have been applied more and more widely. Data 
received by airborne GPS, can define the position of photography station. And the coordinates of photography station are very 
similar as the coordinates of control points in the field. We can do block adjustment by using of the coordinates of photography 
station to reduce a lot of ground control work. Aerotriangulation is a major procedure of aerophotogrammetry. This article, taking the 
Spanish project as an example, will introduce the methods and application of automated aerotriangulation by means of Intergraph 
ISAT software and GPS\INS(IMU) aid for the DMC images. 
1. INTRODUCTION 
ISAT(ImageStation Automatic Triangulation) is software 
developed by US Intergraph company. It is software that 
performs automated aerotriangulation from digital aerial images. 
Its function is to automate point transfer and tie-point 
measurement operations, reduce manual work and perator 
intervention, thereby increase work efficiency. For more 
convenient and efficient processing, ISAT can divide large 
projects into small blocks of photos. It can process whole blocks 
or logical groupings, of photos. Block processing has great 
flexibility. It can perform automatic triangulation on only one 
part of a larger project, or process parts of the project separately 
to more efficiently isolate and solve problems. At the end of 
ISAT workflow, you can merge all processed blocks 
measurement results into master project for the final adjustment 
step for all photos. 
This article will take Spanish aerotriangulation project, 
GPSMNS(IMU) aid for the DMC images as an example. GPS 
means Global Positioning System, INS means Inertial 
Navigation System and IMU means Inertial Measurement Unit. 
2. OPERATING ENVIRONMENT 
Hardware: ISSK(ImageStation Stereo Softcopy Kit), from 
Intergraph Corporation. 
Software: Intergraph ISAT. 
Data materials: DMC digital aerial images supplied by Spanish 
company, camera calibration reports, photo center coordinates 
(GPS/INS(IMU) Extensive Orientation parameters), ground 
control points and technical specification. 
When work with an ISAT project, The project photo images 
must be either all grayscale or all color; all images must have 
the same scan resolution (pixel size); every image file must 
contain a full set of overviews. Before start the ISAT workflow, 
the project must contain EO parameters, or approximate EO 
parameters created by Strip Wizard command, or from flight 
plan or acquired other methods. In this way, the project will 
have enough information to define the approximate position of 
photos and ground control points, as can be confirmed by 
opening the Footprint Viewer (Tools menu) and observing their 
predicted locations. 
3. WORK METHODS 
3.1 ISAT Set Up the Project 
Use the New Project(set up coordinate system and other 
parameters), Camera Wizard, Strip Wizard and Edit Control 
Point or Input Control Point command to set up the project for 
ISAT, input GPS/INS(IMU) EO parameters. 
When using Strip Wizard to edit the flight line, we must define 
IDs(without strip IDs, the auto-matching not able to be 
executed), define photo IDs and image paths, and so on. 
For DMC digital aerial images, there is no PPA(Principal Pt. of 
Auto collimation), no lens distortion correction, no need to do 
interior orientation. When using Camera Wizard command 
(setup camera file), For Camera Type menu, click Digital, then 
import Focal Length to Camera Data menu. 
Use EO,GPS/INS,POSEO command(Translators menu, Import 
submenu) to input GPSMNS, select GPSMNS, then input the 
parameters into relevant column, If there is time parameters, set 
the column of it. For Std Dev, click and input figure according 
to the accuracy of this project(See Figure 1). 
After set up the project of ISAT, use Footprint Viewer 
command(Tools menu) to check if the photo images overlap is 
correct or not, check the position of the first and end photo 
image. This step can also check the input EO(GPSMNS) 
parameters is correct or not.