Photo 1. Taking Photographs from a balloon 
alone, and several percent reduction of time and cost of 
whole construction projects. 
2.5 Problem with the System 
The measurement precision and the reliability are high 
because the operator has the antenna of GPS and 
measures on the just points. It is possible to measure by 
installing an antenna in the vehicle in the place with flat 
shape. However, there is seldom such place, the most of 
measurement must be done in the place which is wealthy 
in the heave. As the problem of this system, the following 
points are given. 
1) The measurement in the steep slope and so on is 
dangerous. 
2) Depending on the landform, the measurement 
sometimes becomes impossible because the GPS 
receiver cannot catch the sufficient number of GPS 
satellites or the radio signal which is broadcasting revision 
data cannot be received. 
3) The measurement in the construction site while 
construction machine’s being operating is dangerous. 
3. A THREE-DIMENSIONAL MEASUREMENT SYSTEM 
USING DIGITAL STILL CAMERA 
3.1 System Configuration 
The authors have also developed a three-dimensional 
measurement system using digital stil camera by 
introducing close-range remote sensing technology to 
survey topography on the construction sites. 
The measurement process is shown below. 
1) Take stereophotographs of the target area using a 
digital still camera from a aerial balloon (see Photo 1). 
2) Input the image data thus obtained into a general 
purpose computer (EWS) by way of memory cards. 
3) Display the input stereoscopic images on a CRT where 
the operator choose several sets of coordinates to be used 
as control points (see Photo 2). 
4) Carry out orientation, matching and other processing on 
264 
  
Photo 2. Input of the control points coordinates 
the basis of the coordinates of the control points to obtain 
data on three-dimensional geometry. 
3.2 Evaluation of the Accuracy and the Efficiency 
Accuracy of the System: 
When taking photographs by the digital still camera of 
1,600,000 picture elements, the coordinate precision is 
about 1/2500 of the photography range. For example, in 
case taking 100m all sides photographs, the coordinate 
precision becomes 4cm. The calculation error with area 
and volume is about 2% comparing with the conventional 
methods. The precision and reliability of this system are 
worse than the RTK system and so on but enough for the 
measurement of earthwork . 
Efficiency of the System: 
This system makes it possible to measure the dangerous 
area as it isn't possible to measure by the RTK system. 
Without entering such dangerous area, the object can be 
measured by remote control photographing and computer 
analysis. Use of a camera capable of recording digital 
images eliminates the need of analog-to-digital conversion, 
thereby solving the problems of image quality and special 
hardware requirements. It is therefore possible to process 
the measurement data in real-time. 
3.3 Problem with the System 
The problem of this system is shown below. 
1) Actually, a lot of time must be spent on the preparation 
before raising the balloon and taking photographs. 
2) The operators control the balloon having the ropes 
which stretch from the balloon on the ground . Therefore, it 
is not total remote work actually, and the measurement 
becomes impossible in the place where the operators 
cannot enter. When becoming photography from the slant, 
the precision of the analysis becomes worse. 
3) When the wind velocity becomes more than 8 m/s, the 
control of the balloon gets difficult and it isn't possible to do 
work. 
   
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