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Title
Close-range imaging, long-range vision

(3) No field works except image acquisition 3.2 Image Acquisition by a Digital Camera
It takes a great deal of time and cost to conduct a ground
survey of control points. A ground survey of control points Image acquisition by a digital camera is the most important
is overinvestment in respect of accuracy in most cases of operation of our proposed method. There are three ways of
digital camera application. Moreover, in case of geological image acquisition by a digital camera in the method.
survey at a construction site, there is a limited time for field
works at a site. According to our method no field works
except image acquisition are necessary at a site and it is
easy for an amateur photographer to take necessary images.
(4) Provision of products of the requested quality
Several precision levels of a geometrically corrected image
are requested according to diverse application fields.
Higher precisely corrected images are required to make an
appropriate preservation or restoration plan of a cultural
heritage. On the other hand, geological survey at a
construction site allows rather lower spatial accuracy of a
rectified image of a slope. Since our method adopts three
ways of image acquisition by a digital camera mentioned
below, geometrically corrected images with several
precision levels can be created with appropriate workload
corresponding to user requests.
(1) Conventional stereo image acquisition
Camera axes of the adjacent images are parallel to each
other, and the area covered by each image overlaps part of
the coverage of its adjacent image to take a stereo pair
image covering all over the object. A scale such as a staff
in leveling is taken in a pair of stereo images to give a scale
of a geometrically corrected image. This is the highest cost
way.
(2) Image acquisition for a plane object
When the object can be treated as a plane, a digital surface
model (DSM) is not necessary to create a geometrically
corrected image. Therefore overlapping ratio of the adja-
cent images can be less than 50 percent. Our proposed
method is as follows: A pair of scales such as staffs in
leveling laid in parallel on a target plane is photographed in
both sides of an image as shown in Figure 2. A scale
photographed in the left side of the image is photographed
in the right side of the left neighbor image, and a scale
photographed in the right side of the image is photographed
in the left side of the right neighbor image. Figure 3 3)
illustrates acquisition of a series of images with a pair of
scales. Image 1 and Image 3 have Scale I in the left side
and Scale II in the right side. In reverse, Image 2 and Image
4 have Scale I in the right side and Scale II in the left side.
3. OPERATIONS OF THE METHOD
3.1 Operation Flow
Operation flow of our method is similar to one of a conven-
tional method by analog/analytical photogrammetry. Figure 1
shows the flow of the standard operation of the method.
These movements of a pair of scales are the same as the
movements of staffs in leveling. This gives geometric
Il controls such as length and linearity in orientation of images.
Furthermore this ensures that there is no gap between
adjacent images. Proposed overlapping ratio of the adjacent
images is 5 to 10 percent. This is the lowest cost way.

L Image acquisition by a digital camera d At site


| Measurement of image coordinates of points |
Ju
ü Orientation of images In office






| Creation of a geometrically corrected image |

Left Center Right
Figure 1. Operation flow
Pos
Figure 2. Image acquisition for a plane object
as (
cor




Coverage of Image 3
Coverage of Image 1
Coverage of Image 2
Coverage of Image 4 poi
Figure 3. Acquisition of a series of images with a pair of scales
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