DISCUSSION ON THE GENERATION METHOD OF SIMPLIFIED TRUE ORTHO
AT THE URBAN AREA
USING THE AREA SENSOR TYPE DIGITAL AERIAL CAMERA “DMC”
K. Yamada * *, M. Oda?
* Kokusai Kogyo Co., Ltd., Asahigaoka 3-6-1 Hino-city, Tokyo, Japan
keiji_yamada@kkc.co.jp
michio_oda@kkc.co.jp
KEY WORDS: Photogrammetry, Acquisition, Orthorectification, High resolution, Urban, Economy
ABSTRACT:
In this study, We applied the true orthophoto obtained by combining the aerial photograph having high overlap ratio taken by area
sensor type digital aerial camera “DMC” with the generation method effectively using the vector data to the fundamental data used
by the administration to get rid of the narrow road of the width of 4 m or less at the urban area. We are planning to utilize this
method for the business to confirm the application for construction. We discussed the simplified generation method of true
orthophoto availing this opportunity as an example.
1. INTRODUCTION
Since the digital photogrammetry system has been disseminated,
the digital orthophoto which is corrected of the distortion of
aerial photograph resulting from undulations of ground has
been widely used for the applications such as backdrop image
of GIS as the products that are obtained easily at lower cost
comparing with vector data. On the other hand, the true
orthophoto which can correct not only the undulations of
ground but also detailed distortion of buildings, etc. is not much
used for the applications as it is rather costly and requires
extremely detailed DSM. As a result, the true orthophoto is
positioned by very special and costly product and is used in
many cases for the state-of-the-art projects.
In this study, we attempted to generate true orthophoto at
relatively low cost using highly overlapped photographing by
aerial digital camera and simplified generation method with the
relative detail corresponding to the use purpose and apply it to
the project for the construction of basic data of administration
in an aim to eliminate the narrow roads in the urban area.
2. PROBLEM OF NARROW ROADS IN THE WARD
AREAS OF TOKYO
The existence of narrow roads with the width of 4 m or less
creates obstacles for the smooth traffic and formation of good
urban environment, disturbs the smooth evacuation and rescue
activities at the time of disaster such as fire or earthquake, and
brings about threats to the livelihood of citizens. Also, the
buildings are crowded in most areas of narrow road, creating a
big problem for the disaster prevention at urban areas.
These narrow roads at the urban area should have been weeded
out at the time of re-construction of building by the premise set
back system specified by the Construction Standard Act
enforced in 1950, and after 50 years from such legislation, it
has been considered that the majority of narrow roads had
already been removed. However, many narrow roads are still
existing in the ward area of Tokyo. At the periphery of Honcho
of Shibuya-ku, for example, the ratio of narrow roads against
total length of road is as high as more than 50%.
The following reasons can be pointed out for the reason why
the present situation has been created.
e These roads are private road and it is hard to identify
these roads because access to it is difficult.
e [tis difficult to confirm the center line of these narrow
roads, and the position of set back cannot be
determined at the time of reconstruction control of
building.
e Although set back is made at the time of
reconstruction of building, the space generated by it is
not secured as the road space (construction of L-
shaped side groove, etc.).
Typical narrow roads around Shibuya-ward are shown in figure
1. Image on the left shows one of private narrow road, image
on the right shows condition of shadow at narrow road.
Figure 1. Condition of typical narrow road
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