University
enia.
(in
PHOTOGRAMMTERY AND GPS TECHNOLOGY ASSITING THE ACQUISITION OF
ROAD GEOLOCATION AND GEOMETRY
Uros Ranfl
DFG CONSULTING, d.o.o., Pivovarniska 8, 1000 Ljubljana, Slovenia — ura.dfg(a)moj.net
Commission VI, WG VI/3
KEY WORDS: GPS, photogrammetry, digital video, state roads geometry
ABSTRACT:
Georeferenced data present state of the art in the road data management. They are accessible directly in state co-ordinate system and
therefore easily connected into existing geospatial databases. In this paper we present the concept, technology, possibilities and
practical experiences on a low cost mobile mapping system (named VideoCar) developed for road data acquisition in Slovenia.
Accurate georeferenced measurements of road width and geometry and various data of road equipment are achieved by combining
stereophotogrammatery and GPS technology. Applied techniques and procedures ensure georeferenced data in relatively short time
countrywide. Capturing road data with the system offers quick and reliable method for updating road databases.
1. INTRODUCTION
Georeferenced measurements of road geometry and road
objects present a new concept in generation of road databases.
Road databases in the past were linked into object space
through a chainage system. Organisation of road data based
upon length measurements from the appointed node did not
connect database records into the state co-ordinate system. Data
not connected into the co-ordinate system present obstacle in
efficient road data management and make them impossible to
link into GIS platforms. It is also impossible to include these
data into modern navigation systems such as GPS technology.
Therefore georeferenced data are required. Georeferenced data
present state of the art in the cost efficient road data
management. They are accessible directly in the state co-
ordinate system and therefore easily connected into existing
geospatial databases. An application of georeferenced data also
offers further analyses in GIS environment. The realisation of
such GIS in road management is influenced by many data
acquisition problems. Capturing up to date road data requires a
time-consuming fieldwork especially if data is needed for larger
area.
A possible solution offers integration of video technique with
integrated GPS/INS system. Inertial navigation system is
electronic system that continuously controls position and
acceleration of an object and collects navigational data without
connection to the base station. Data capture is performed by
means of mobile unit with mounted two digital video cameras
and navigation subsystem (GPS). Integrated GPS/INS systems
present most recent solution in geolocation acquisition but this
is quite expensive technology. We decided to choose a low cost
variant that still assures accuracy in our framework. It was used
a combination of digital magnetic compass, an inclinometer and
an odometer instead of expensive INS sensors.
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2. DESIGN OF MOBILE MAPING SYSTEM
VIDEOCAR
The mobile mapping system VideoCar integrates vehicle, video
cameras, a GPS receiver, an odometer and digital compass
module. The Global positioning system determines the
trajectory of the vehicle that approximates the centre of the
road. The loss of GPS signal is overcame by alternative
positioning system by means of digital compass and odometer
measurements. The position data and the digital image records
are synchronised in the GPS time frame to enable
georeferencing of the captured imagery. Accurate
georeferenced measurements of road width and geometry of all
other objects on and beside road are achieved by digital
stereophotogrammetry techniques.
[7
Figure 1. Mobile unit with mounted sensors
2.1 Video system
Video system consists of two digital video cameras with
mounted wide converter to achieve larger field of sight. Video
cameras are placed in special waterproof cases mounted on the
top of the vehicle. Both of the cameras are linked to video port
on computer to control camera operation and image capturing.
