Abstract
By using a digital photogrammetric system, DEMs (Digital Elevation Models) and ortho-images can be made at the same time from remote sensing stereoscopic images. Moreover stereoscopic animations can be made from these data easily. Usually stereoscopic animations are made by moving the positions of looking eyes, but newly proposed stereoscopic animations are made by changing the interval of two looking eyes, that is, by changing the B/H (Base /Height ) ratios of component stereoscopic images. The usefulness of the new kind of stereoscopic animations has already been shown in the field of earth resource exploration. In this paper, the utilization of the two kinds of stereoscopic animations in the field of route selection is produced. Lineaments, which can be extracted effectively from the new kind of stereoscopic animations, can be of service in the work of funnel route selection. The usual kind of stereoscopic animations can be used to good effect in the work of long road route selection. By using these stereoscopic animations, the cost and time consumed in route selection work can be reduced greatly.

Introduction
Birds eye view images or animations are often used on image processing systems, because they do not require any special display devices such as liquid crystal shutter glasses. But it is impossible to extract detailed topographic information from them. For detailed topographic information, stereoscopic images or animations are necessary. There have been some reports showing the usefulness of stereoscopic images in some fields such as earth resource exploration or route selection(1), but there are few reports showing the usefulness of stereoscopic animations. Stereoscopic animations indeed have an ability to be useful in many application fields. The usefulness of stereoscopic animations in the field of road route selection will be shown here. 

A method to make stereoscopic animations from stereoscopic images
There have been many stereoscopic animations made using computer graphics techniques, but few made using DEMs and ortho-images. In order to extract detailed topographic information from remote sensing images, the latter is necessary. Usually it is not easy work to make stereoscopic animations using DEMs and ortho-images, because the two component data can not be obtained. However, recently a new method has been developed to easily extract the two component data at the same time by digital photogrammetric system(2).

Figure 1 shows a method to make stereoscopic animations from stereoscopic images. In the Figure, DEMs and ortho-images are extracted from stereoscopic images at the same time using the method mentioned above. Then some useful maps are obtained on the ortho-images, and finally stereoscopic animations are made using the overlaid ortho-images and the DEMs.


Figure 1 A method to make stereoscopic animations 

Advantages of stereoscopic animations in lineament extraction
A lineament, which means a linear feature on the earth's surface, is very important information for mineral vein finding because it sometimes shows the existence of a fault. In the field of earth resource exploration, lineament extraction from remote sensing images is a very important theme, and has been researched actively. The relationship between the B/H ratios of stereoscopic images and the total amounts of lineaments which can be extracted from the stereoscopic images, had already been researched. One research has been carried out at lzu peninsula and Hisshikari district in Japan (4). Figure 2 is a part of the research which shows the lineaments extracted from 4 pairs of different B/H ratio stereoscopic images of lzu peninsula.

As a result of this research, some principles have been extracted as follows. 
(1) the greatest amount of lineaments were extracted from 0.5 B/H ratio stereoscopic images at lzu peninsula where the slopes of the earth's surface were steep, but at Hishkari district where the slopes were gentle, 1.0 B/H ratio stereoscopic images were the best. It can be said from these facts that the most suitable B/H ratio of stereoscopic images for finding many lineaments is different according to the steepness of the earth's surface. 
(2) the lineaments which were extracted from 4 different B/H ratio stereoscopic images were slightly different. So, it can be said that different lineaments can be extracted from B/H ratio stereoscopic images. 

Figure 2 Results of lineaments extraction from 4 different B/H ratio stereoscopic images of lzu peninsula.

It can be said from the result shown above that it is necessary to use many different B/H ratio stereoscopic images to extract the greatest amount of lineaments at each place. However in practice, it is very difficult to make and use many stereoscopic images. In order to resolve this problem, a kind of stereoscopic animation has already been proposed(3). In the stereoscopic animation called stereoscopic animation of rising mountains, the mountains as virtual images rise or sink slowly by changing the B/H ratios of the component stereoscopic images gradually.

Application of stereoscopic animations to route selection
The usefulness of stereoscopic animations in the field of earth resource exploration has been shown above, but they can be used in the field of road route selection as will be shown next.

In tunnel construction, faults must be avoided carefully. A map of already confirmed faults is surely very useful, but usually there are many other unknown faults even in fairly developed areas, and detailed ground inspection by boring is usually necessary. It is proposed here to use lineament information in the work of tunnel route selection. The technique of lineament extraction from remote sensing stereoscopic images has already been developed in the field of earth resource exploration, and the usefulness of stereoscopic animations of rising mountains has already been shown. The technique and stereoscopic animations can be used effectively in the field of route selection also. Slow motion or step motion of the stereoscopic animations should be necessary to find carefully new lineaments across the route of a planned tunnel. Figure 3-7 show one example of these stereoscopic animations. 



Figure 3 is a map of already confirmed faults at lzu peninsula. Figure 4 is a map of main roads. Figure 5 is an overlaid ortho-image. A stereoscopic animation has been made using this overlaid ortho-image and a DEM. Figure 6 is a one pair of component stereoscopic images of the stereoscopic animation. Figure 7 is another of larger B/H ratio. A stereoscopic animation of rising mountain is composed of such different B/H ratio stereoscopic images.



Another kind of stereoscopic animations, which are made by moving the positions of looking eyes, are also useful to select long road routes at long areas that can not be displayed on a monitor at one time. The B/H ratios of the stereoscopic animations must be selected carefully to extract necessary information easily. For instance, a large B/H ratio may be suitable in a mountainous areas to check the inclines of roads on a mountainside carefully. If it is necessary to examine exact inclines, another tool can be used as shown in Figure 8. the profile of the earth's surface under the line which has previously been drawn by a mouse is shown on the display with the animation, and the exact incline of the route can be calculated easily from the profile.



It is very expensive work to gather necessary information for route selection on the ground especially in undeveloped areas, but most can be replaced by computers using stereoscopic animations and other tools. Also the cost and time consumed in the route selection work can be reduced substantially. 







Conclusion
Stereoscopic animations can be made from stereoscopic images directly and easily by using digital photogrammetric system, and can be used effectively not only in the field of earth resource exploration but also in the field of route selection. A kind of stereoscopic animations, which are made by changing the B.H ratios of component stereoscopic images, are useful to find new lineaments, and can be used effectively in the work of tunnel route selection. Another kind of stereoscopic animations, which are made by moving the positions of looking eyes, can be used effectively to select long roads routes at long areas that can not be displayed on a monitor at one time. Bu using these stereoscopic animations, most work on the ground can be replaced by computer work in a room and the cost and time consumed in route selection work can be reduced greatly.

References

1. N.Mori, H. Takaoka, K. Tonoike, J. Komai, S. Murai, 1988; Investigation of the Effectiveness and Applications of Japanese ERS-1 Stereoscopic images; ISPRS, Kyoto, Japan, Vol. 27, Com.1, pp. 109-119.
   
2. N.Mori, 1997; An Ortho-image Production Method from Stereoscopic images ; ACRS, Kuala Lumpur, Malaysia, pp.1.6..1~1.6.6
   
3. N.Mori, 1998; A new Method to Make Ortho-Images and Stereoscopic Animations; ISPRS, Halkodate, Japan, Vol.32.Part 5, , pp.894-899.
   
4. N.Mori, 1998; A new Method to make Stereoscopic Animations and Their Applications; ACRS, Manila, Philippines, pp.Q.10.1~Q10.6