2004 
nts of 
r and 
in a 
'nsors 
aser). 
ferent 
eived 
ignals 
ystem 
is to 
(GPS 
SS; ds 
data 
1: the 
ich is 
| time 
To is 
sm or 
> but 
1, the 
| and 
ensor 
) sets 
ation 
n the 
two 
on to 
s the 
point 
neras 
P the 
n the 
1 the 
)BIL 
on is 
ation 
'nced 
ages 
f the 
owed 
1etric 
was 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
considered too expensive and the actual system is not stereo. 
For each pair, each image is visualized in a view and the 
operator should identify the point to be measured in both 
images. Vector data can be superimposed on top of the images. 
The system is based in MicroStation 95 and the customization 
has been developed using MDL language. The system 
functionality for image and vector visualization, data 
digitalization and editing or data storing takes advantage of the 
MicroStation basic tools. As the same tools are used in data 
compilation, editing and storing for other topographic databases 
created at the Institut Cartografic de Catalunya, data integration 
can be achieved without any data transformation. 
The application allows the reproduction of the path covered by 
the GEOMOBIL, visualizing the sequence of images collected 
by each camera. The path information is obtained from a file 
with the position (geographic coordinates in a given reference 
system) and attitude of the projection center for every photo. 
Another file provides information about the parameters for the 
cameras (focal length, principal point coordinates, radial 
distortion and internal orientation). 
Each image sequence is visualized in a MicroStation view. The 
view is configured according to the camera (coordinates and 
angles of the projection center, coordinates of the principal 
point, and focal length), and the image is placed in the 
perpendicular plane to the camera axis at a selected distance of 
the projection center. This method allows the visualization of 
georeferenced data on top of the image. 
Two views of MicroStation can be used to show the path, the 
projection centers and the orientation of the visualized images. 
Vector data and raster images can be also displayed in these 
views. As no more than eight views can be used in 
MicroStation, a maximum of six sequences can be visualized 
during a session. 
ue Ne ttc 95 
ET n 
i 1V-LTA4 LC-SDUCU-9 TP Cebtes « 
  
  
Figure 4: Screen shot of the GEOMOBIL data 
extraction software. 
The tools for image management allow to advance and to go 
backwards one image in one or more views, to select one image 
in one view, to synchronize the images for all the views, and to 
go to the nearest image to a georeferenced point. The 
visualization tools, as zoom in, zoom out, center the view to a 
given point, or fitting the image in the view, have been 
specially developed for this application, because MicroStation 
standard visualization tools do not preserve the camera 
configuration. 
The point coordinates are calculated resolving the collinear 
equations {rom the position identified in two images. The 
images can be amplified to facilitate the point identification, 
and the epipolar line can be visualized, after giving the point in 
the first image, to identify the same point in the second image. 
The collinear equations solution is computed in geocentric 
coordinates to increase the accuracy, and then it is converted to 
the work reference system. 
The coordinates of the calculated point are sent to MicroStation 
to be processed by the active command as a standard input. 
Microstation commands and other specific tools can be used to 
capture new data or to modify existing information. A set of 
tools has been created to gather elements tied in the roads. They 
allow to capture the axis of the route, to attribute it with some 
characteristics (number of rails, tunnel, street...) and to capture 
attached elements to the road as kilometric points, traffic signs, 
gas stations or bus stops. 
3. GEOMOBIL IMAGE SUBSYSTEM CALIBRATION 
3.1 Camera parameters calibration 
Calibration of the optical parameters was carried out at the [CC 
facilities. 
The floor of the ICC exposition room has a regular pattern (as 
can be seen in image 5). Using classical surveying techniques, a 
local reference frame was set in the exposition room. The 
coordinates of six points on the ground in the local reference 
frame were measured. The position of each camera was 
computed on up to six different sites around the target area on a 
balcony situated at 8.40 meters above the target area. From each 
of these sites both cameras were operated to image the target 
area. 
    
Figure 5: setting of the camera calibration site. 
Up to 471 points were identified in the images of the target 
area, with in a total amount of 4165 photogrammetric 
observations (average of 347 photogrammetric observations per 
image). Six of the 471 points are the six measured points 
mentioned above. These six points become six full control 
points. The other 465 are vertical control points at height zero 
(in the local reference frame). Moreover, due to the regular 
pattern and distribution of points, a distance restriction between 
the adjacent points of the 471 point network was imposed.