Osamu Akutsu*, Ryosuke Shibasaki**, Bokuro Urabe*
*Geographical Survey Institute, Ministry of construction
**Center for Spatial Information Science, University of Tokyo
1 Kitazato, Tsukuba, Ibaraki 305-0811, Japan
Tel: 81-298-64-5913 Fax: +81-298-64-3056
In recent years, the use of Geographic Information System (GIS) is increasing rapidly among the various fields and users, such as the government, corporations, and general users. In such a circumstance, GSI should provide geographic data not only in raster-base but also in vector-base.
It needed time and labor to acquire the position data in 2 dimensions or 3 dimensions. Recently, using an electronic flat board and GPS, real-time GIS data acquisition has become available. However, since it is using GPS, this system is quite expensive, and data acquisition is almost impossible in urban area.
Considering the situation above, it is necessary to develop economical simple-type Mobile interface system, which can easily and rapidly acquire GIS data in such urban area.
Figure 1 Data acquisition flow
The author develop a system to take data from lasers, magnetic azimuth sensors, gyro sensors and GPS into the personal computer (PC) by the interface of RS232C. The system uses WIN32API to handle those data with PC. It is possible to handle data by using PCMCIA (PC card).
First, this system measures initial value (X0,Y0,Z0) at a point where GPS can be used, it coordinates are unknown.
Next, it measures positional relationship between the original point and unknown points, distance (d) by the laser, tilt (f,w) by the gyro sensor, azimuth (q ) by the magnetic azimuth sensor. Though the gyro sensor can measure an azimuth, it has a large drift error, so this system uses a magnetic azimuth sensor.
This magnetic azimuth sensor is a three-axis digital magnetometor which detects strength and direction of the magnetic field, and sends the x,y and z component directly to the computer. This sensor is made up of thin strips of permalloy (NiFe) magnetic file ) whose electrical resistance varies according to the change of applied magnetic field.
The calculation of azimuth is described in figure -2.
Bx = Bcos q
By = Bsin q
q = tan-1(By/Bx) Azimuth (x=0,y0) =270.0