International Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 5. Hakodate 1998 
A NEW METHOD TO MAKE ORTHO- IMAGES AND STEREOSCOPIC ANIMATIONS 
Nobuhiko MORI 
Professor, Faculty of Information Science 
Osaka Institute of Technology 
1-79-1, Kitayama, Hirakata-shi, Osaka, 573-0196, Japan 
E-mail: nmori@ij.oit.ac.jp 
Commission Y, Working Group SIG 
KEY WORDS: Ortho-image, Digital photogrammetric system, Stereoscopic animation, Landscape, Lineament 
ABSTRACT 
An ortho-image production method has been developed, which makes an ortho-image from stereoscopic 
images directly. The method has been realized by changing a DEM (Digital Elevation Model) extraction software 
a little in a digital photogrammetric system. In the method, the pixel values of the output ortho-image can be 
calculated using those of two input images, and some image corrections, such as partial replacements and 
arithmetical calculations on two input images, can be carried out to make a fine output of an ortho-image. So, it 
is easy to make an ortho-image without clouds and shades from satellite stereoscopic images. Using this 
system, it is very easy to make stereoscopic animations, because both an ortho-image and a DEM can be 
obtained at the same time, and the positions of their elements are completely the same. Two kinds of 
stereoscopic animations are proposed here. One is a stereoscopic animation of landscape, which is useful to 
grasp detailed topographic information of subject areas. The other one is a stereoscopic animation of rising 
mountains, which is useful to extract such features of the earth's surface as lineaments. These stereoscopic 
  
animations can be used effectively in many application fields. 
1. INTRODUCTION 
At present, three-dimensional (3-D) animations are 
very popular in TV programs and games. But 3-D 
animations of landscape are not so popular, because it 
is very difficult to get these two kinds of essential data 
of subject areas, fine ortho-images and DEMs of 
appropriate interval. Ortho-images are usually made 
using DEMs and images with orientation elements. 
Those DEMs are very often extracted at appropriate 
interval from topographic maps with contour lines, 
because there are few kinds of available DEMs now. 
There are many proposed methods to extract DEMs 
from contour lines automatically by a computer. DEMs 
can be extracted from stereoscopic images also by a 
digital photogrammetric system. There are now many 
commercial digital photogrammetric systems in the 
world (Armin Gruen, 1996). To make ortho-images, it 
is necessary to take two steps, a DEM extraction and 
then an ortho-image production. This is the reason 
why ortho-image production is cumbersome and 
scarcely carried out. In this paper, one method to 
make both a fine ortho-image and a DEM at the same 
time will be shown. Then, two kinds of stereoscopic 
animations, landscape and rising mountains, will be 
proposed as useful tools for designing of area 
development and feature extractions. 
2. AN ORTHO- IMAGE PRODUCTION METHOD 
FROM STEREOSCOPIC IMAGES 
As mentioned above, a DEM is necessary to make an 
ortho-image by conventional methods. But now, it is 
possible to make an ortho-image from stereoscopic 
images directly using a new method (Mori, 1997). In 
addition to the ability of extracting a DEM from 
stereoscopic images, the digital photogrammetric 
system with the method can produce an ortho-image 
also from the same stereoscopic images. Figure 1 
shows the method to make an ortho-image from 
stereoscopic images directly. In the figure, the left 
image and the right image compose a pair of 
stereoscopic images, and are placed on the position 
where the images were taken. O' is the perspective 
center of the left image, and O" is the one of the right 
image. These positions of the left image, O', the right 
image and O" can be determined by doing orientations 
of both images. P is a point on an object. P' is the 
corresponding point of P on the left image, and P" is 
the one on the right image. The position of P can be 
determined as the cross point of two lines, O'P' and 
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