ution. In: 
in region. 
  
Yasuyuki Shirai 
  
FUNDAMENTAL STUDY ON REAL TIME MEASUREMENT OF ALTITUDE DATA WITH 
ACCELEROMETER AND VEHICLE SPEED SENSOR 
Yasuyuki SHIRAT, Toshio KOIZUMI *, Atsuro TAKEMOTO"", Ichiro ADACHI 
‘Dep. Precision Eng., Associate Professor, Chiba Institute of Technology, Japan 
e shirai @ pf.it-chiba.ac.jp 
“ Dep. Civil Eng., Professor, Chiba Institute of Technology, Japan 
ke koizumi @ce.it-chiba.ac.ip 
~ Computer Center, Associate Professor, Chiba Institute of Technology, Japan 
e atakemoto Q pf it-chiba.ac.jp 
- Dep. Civil Eng., Professor, Chiba Institute of Technology, Japan 
adachi@pf.it-chiba.ac.jp 
Working Group V/2 
KEY WORDS: Inertial navigation system, Accelerometer, Vehicle speed sensor, Altitude, Platform, Mobile. 
ABSTRACT 
The background of this research is in the easy measurement of the difference of elevation of the surface of the earth in 
the developing countries. The leveling is being measured by generally using the level and GPS now. However, there are 
times when the measured range is wide-ranging and in the urban area and the mountain where the electric wave does 
not reach easily, are difficult in the level and GPS. Then, if the difference of elevation can be measured by installing the 
inertial device in the vehicle, the leveling of the large area easily becomes possible. Because a inexpensive gyro had the 
fault with low accuracy in a past inertial survey, the method of not using the gyro was examined. Then, this study 
developed the method of obtaining the difference of elevation by using the accelerometer and the vehicle speed sensor. 
1 INTRODUCTION 
One of the most important assignments in mobile mapping is to measure in real time the altitude of a platform with 
camera and others mounted thereon at a higher accuracy. GPS is one of the effective means for positioning the platform. 
However, the GPS is rather poor in the altitude defining. Further, it is difficult to use the GPS in mountains and urban 
areas that are beyond the radio wave range. Though the inertial photogrammetry using accelerometers and gyros has 
been studied, the accuracy of the inertial survey does depend largely on the gyro. Any gyros with high accuracy are 
exceedingly expensive. Their availability is much limited. In this paper we are going to introduce a methodology we 
developed that will allow us to obtain, at lower cost, altitude data with rather high accuracy using accelerometers and 
vehicle speed sensor. Only the gravitational acceleration of the earth acts on any accelerometers at rest installed on three 
orthogonal axes: X, Y, and Z. When displaced on a slanting surface, however, the resultant of the acceleration 
accompanying the displacement is calculated out as a resultant force of the acceleration acting on the accelerometers on 
the respective axes. Further, this resultant force is computed as the resultant of the gravitational acceleration of the 
earth, vertical and horizontal accelerations. The acceleration of the platform in its progressing direction is calculated as 
the resultant of its vertical and horizontal accelerations. From these, the vertical acceleration becomes the function of 
the resultant force of triaxial accelerometers, the acceleration in the progressing direction, and the gravitational 
acceleration of the earth. The computation of the acceleration in the progressing direction will therefore allow us to 
calculate out the acceleration in the perpendicular direction and accordingly the height of the slanting surface. The 
acceleration in the progressing direction was calculated in our study using a vehicle speed sensor. According to the 
theory thus far described, we attempted an experiment on an actual road with some level differences to verify and 
justify the theory. The experiment used an automobile and a bicycle-drawn cart, both provided with sensors to describe 
the longitudinal sectional drawings of the road. The results were compared with those by direct leveling. The road on 
which the experiment was conducted was a road with asphalt pavement, approximately 160 m in horizontal distance 
and about 6 m in level difference. Three sorts of comparisons were made between the accelerometer and vibration gyro, 
accelerometer and fiber optical gyro, and accelerometer and vehicle speed sensor. The descending order of accuracy 
was the accelerometer with vehicle speed sensor, with fiber optical gyro and with vibration gyro. The experiment could 
demonstrate the justification of the theory the authors have proposed. This enabled us to manufacture equipment that 
measures in real time the altitude of a moving platform by means of accelerometers and vehicle speed sensors. We will 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B1. Amsterdam 2000. 301