ifi- 
ed 
ed 
si- 
for 
An- 
jis- 
ch, 
pp. 
atic 
ata, 
ee- 
DIE 
fa 
Ge- 
lec- 
Ex- 
ace 
Jigi- 
rne 
tion 
sing 
11- 
SyS- 
leek 
lich- 
195]: 
Aan- 
allite 
ects 
bler, 
asel, 
natic 
Digi- 
o. 4, 
DEVELOPMENT OF A DIGITAL-IMAGE-BASED-PLOTTER 
AND ITS APPLICATION TO GROUND DISPLACEMENT MEASUREMENT IN THE KOBE EARTHQUAKE 
Susumu Hattori, 
Atsushi Okamoto, 
Tetsu Ono, 
Hiroyuki Hasegawa 
Assoc. 
Assoc. Prof., 
Prof, 
Assistant, 
Fukuyama University, Japan 
Kyoto University, Japan 
Kyoto University, Japan 
Senior Manager, Pasco Corporation, Japan 
The ISPRS Commission IWG II/III, Vienna, 1996 
KEY WORDS: Digital-Image-Based Plotter, Digital Photogrammetry, Kobe Earthquake, Ground Displacement, 
Least Squares Correlation, LoG filter, Sobel Filter, Measurement 
ABSTRACT 
This paper describes a digital image-based plotter, GOKUU. GOKUU operates on UNIX and a window system, 
X11 and supports fundamental functions of aerial photogrammetry. Especially it is implemented with the 
least squares correlation for semi-automatic matching of orientation points. It is modified to extend 
the small convergence domain (one pixel) to +5 pixels by extracting strong edge corners using the LoG 
filter and the Sobel filter. GOKUU was applied to the ground displacement measurement in the Kobe 
earthquake, and its measurement ability was tested. The result suggests that the dynamic range of CCD 
sensors of film scanners used and the current quantization level, which is usually one byte (256 
stages), and the dynamic 
range of display monitors are not sufficient to compete with clear 
observability of film-based analytical plotters. Thus unavoidably the actual measurement project was 
completed by an analytical plotter. The paper compared the measurement precision with GOKUU and the 
analytical plotter, followed by the brief explanation of the measurement work and results of ground 
displacement. 
1. INTRODUCTION 
Digital photogrammetry is expected to replace the 
current film based photogrammetry in the near 
future. We have recently developed a simple DP, 
GOKUU on a low level workstation for education and 
training of photogrammetry, especially linked to 
GIS. The OS (Operating System) is UNIX and the 
window system is X11R5. Only the standard 
equipments of a workstation is assumed to run it. 
For semi-automatic measurement of orientation 
points coordinates, the least squares correlation 
(LSC) is implemented. A major shortcoming of the 
LSC is its small convergence domain. We stretched 
it using the Laplacian of Gaussian (LoG) filter 
and Sobel filter. This is called hereafter MLSC 
(Modified LSC). GOKUU adopts the screen split 
method for stereo view with a simple reflectance 
mirror scope. 
In Jan. 17, 1995, a disastrous earthquake broke 
out centered at the Kobe district, West Japan, 
which claimed 45,000 lives. In March, 1995, "the 
committee on damage evaluation for the Kobe 
earthquake" was formed headed by the Geotechnical 
Society. Dr.Okamoto was named to the leader of a 
WG for the measurement of the ground displacement. 
Its objective was the 
photogrammetry using large scale photographs taken 
measurement by aerial 
147 
before and after the earthquake, to which we tried 
to apply GOKUU. 
The damaged area was about 30km*80km wide. It was 
apparently impossible to measure all the area by 
the end of 1995. We selected Ashiya-city, one of 
the most damaged city, as a pilot area for 
measurement. We first planned to apply GOKUU to 
this project entirely. To identify the correspond- 
ing points in the photographs before and after the 
earth-quake, cooperative observation on the screen 
by two operators was thought to be the most 
effective to avoid mis-identification. But in the 
course of experiments, many shortcomings came out. 
Some were due to the design of GOKUU, and others 
were due to limit to digital 
photogrammetry. 
current 
In spite of incessant improvements of GOKUU, the 
time limit to the dead line of report and required 
high precision of measurements, we changed the 
plan to the use of an plotter in 
November, 1995. The measurement was completed in 
February, 1896 and the achievement was published in 
a report (Okamoto et.al.,1996). 
analytical 
describes the constitution and 
GOKUU including the MLSC, and 
discusses the experimental results of measurement, 
when applied to the measurement work in the 
This paper 
functions of 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996