was planned taking into account the configuration of the terrain 
and the day length. 
  
  
  
  
Figure 7. Slovenian state roads and selected reference points 
3.2 GPS survey 
Selected GPS processing method was relative kinematic with 
postprocessing. GPS data registration interval was reduced to 1 
second to assure enough quality data for image georeferencing. 
Average speeds of surveying vehicle were ranged from 39km/h 
to 51 km/h. Vehicle’s speed was adjusted to temporary road and 
traffic conditions. In the optimal conditions (straight road, open 
sky) maximal allowed speed was 60 km/h. Proper velocity 
reduction was applied in less favourable conditions (winding 
road in the woods) where GPS signal interruption appeared. 
The vehicle was stopped after longer period without GPS 
signal. During the stoppage there were usually enough data 
collected to acquire position of the vehicle. 
3.3 Acquiring data from video images 
Prerequisite for quality data acquisition from video images is 
calibration of video cameras. It is also important that the survey 
is carried out in good weather conditions: no rainfall, no fog, 
dry roads, position of the sun far above the horizon. 
Experiences, gained during the project, pointed out that the best 
conditions are in cloudy days without rain when light is diffuse. 
Images taken at these conditions are slightly less contrast but 
there is no harmful effect of direct sunlight. 
4. RESULTS 
During the project, all state roads were passed in total length of 
5896 km (11792 km in both directions) in period of 5 months. 
Eventually there were only 47 days with good weather 
conditions. On videotape was recorded about 310 hours of road 
data. Analysing the results after GPS data processing, we can 
say that for 85% of roads sub meter accuracy of road centreline 
was achieved during the good GPS signal. Using the alternative 
positioning system, the accuracy of centreline was slightly 
reduced. The geolocation accuracy of the tourist signalisation 
was approximately 1m. The quality and reliability of the results 
were approved by superimposition of the data on digital 
ortophotos in scale 1:5000 and an independent control survey. 
From video images 4711 tourist information signs were 
captured. Each sign was georeferenced. On each sign were 
222 
measured the size of the sign, the length from the roadside and 
identified the contents of the sign. It was also identified and 
measured all road contractions. Geometry of road width and 
tourist signalisation was measured within 5 cm accuracy. 
5. FURTHER POSSIBILITIES OF THE SYSTEM 
The system was developed for concrete project and produced 
satisfying results. On the bases of gained experiences, we can 
suggest that this technology could be accepted on many other 
tasks in the field of road infrastructure registration: 
e Updating database of state roads centreline 
e Registration of road centreline 
e Setting the attributes on road categorisation 
e Registration and categorisation of junctions 
e (Cadastre establishment of horizontal and vertical road 
signalisation 
e Registration and analyse of road objects 
e Visual control of road surface 
State road centrelines were acquired with the GPS system in 
ETRS89 co-ordinate system. All Slovenian topographic maps, 
except the latest military maps, are referenced in Slovenian 
state co-ordinate system. Connecting road data to the existing 
topographic maps or their application in GPS navigation is not 
trivial. Road data acquired with VideoCar system can be easily 
transformed into vector roadnetwork map in ETRS89 co- 
ordinate system. Vector roadmap is essential for modern 
navigation systems. 
Applying the technology is possible to use automatic feature 
extraction of traffic signs and attribution of particular road 
sections. With these data, we can create database of speed 
limits, obstacles on road, road contractions, road orientation and 
road categorisation. This database could be used in precise 
route planning and assistance in GPS navigation. Applicability 
of the system could be also approved in traffic security 
improvement. Slightly modified navigation system connected to 
road database (mentioned above) could warn users exceeding 
speed limits or in the near future even automatically reduce 
vehicle's speed. 
Video images does not contain only metric data, but they are 
also full of semantic data. It is possible to capture data about 
road attrition, condition of road and road objects. This 
information could be analysed and used to improve traffic 
safety. 
6. CONCLUSION 
Temporary state and possibilities of the system ensure above 
mentioned results and accuracy. Improvement of 
georeferencing accuracy is still possible by integrating inertial 
measurement systems. 
7. REFERENCES AND ACKNOWLEDGEMENTS 
7.1 References from Websites 
Caruso Michael J., 1997. Applications of Magnetoresistive 
Sensors in Navigation Systems, Honeywell Inc. Technical 
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