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Title
International cooperation and technology transfer
Author
Fras, Mojca Kosmatin

A LOW COST MOBILE MAPPING SYSTEM
A. Vettore, A. Guarnieri
C.I.R.GEO
(Interdepartment Research Center for
Cartography, Photogrammetry, Remot Sensing and GIS)
AGRIPOLIS - Statale Romea 16
35020 Legnaro (Padova)
Phone +39-049-8272688 , fax +39-049-8372713
e-mail: vettoan@uxl.unipd.it
Commission VI, Working Group 3
KEY WORDS: Mobile Mapping, Photogrammetry, GPS
ABSTRACT
In this work an alternative method, respect today’s tipical road survey, is presented. Tipically, a road survey is carried
out by a team composed by three operators at least, that moves with a vehicle on which an odometer is mounted on the
rear in order to measure the effective travelled road. Given this operational procedure, a road survey requires, as a rule,
a lot of time, resulting therefore very laborious and expensive regarding the employement of economic and human
resources. Possible solutions to these problems could be represented by integration of Computer Vision technology with
modern satellite positioning system, as GPS. Also in agreement with this idea, GeoVision, a digital photogrammetric
software for road survey, has been developed at the University of Padua (Italy). The system consists of a van equipped
with two digital cameras, Sony XC75CE recording in continous way the surveyed environment and a GPS receiver that
provides post-processed differential positions. From a pair of correspondent digital images, the 3D position of a feature
can be determined in a global reference system (namely WGS-84), by integration of photogrammetric triangulation
techniques and computer vision algoritms. In following sections the tools regarding digital image processing subsystem
of GeoVision will be described in detail.
1. INTRODUCTION
The use of a geographic information system (GIS) as
decision tool for land and infrastructures management
is even more increasing by public administrations so as
private companies. This has resulted in a demand of a
more precise GIS in planning and in an increasing
demand for efficient data acquisition systems and up
date of existing databases. Therefore all these require
ments make GIS information updating a permanent
task. Traditionally, GIS data acquisition is a laborious
process, requiring digitization of existing maps, manual
data entry during the survey and other time consuming
techniques and therefore have limited the applicability
and uselfuness of GIS to potential users. From this
point of view the automation and speed up of GIS data
acquisition represent a very important issue in cases
where field surveys have to be performed ([3] and [8]).
In order to address the problems of update and reliabi
lity of GIS information, a low cost Mobile Mapping
System, GeoVision, has been developed at the Univer
sity of Padua (Italy). The system is based on a van
equipped with two digital b/w cameras Sony XC75CE,
with a basic format of 768x582 pixels, a GPS receiver
an odometer and an analogue color videocamera. The
CCD cameras, mounted on the front of the vehicle,
record in continous way the surveyed environment: on
one hand they can provide more detailed information
of objects on the earth in comparison to aerial photo
graphs and remote sensing satellite images, on the
other hand CCD images have to be georeferenced in
order to supply 3D information about object position.
To this aim the image acquisition stream is synchro
nized with GPS data collection via the PPS (Pulse Per
Second) signal of the GPS receiver clock: in this way
for each image pair it is possible to recover the geogra
phic position of the cameras at the time of the shot.
When signal blockages or poor GPS satellite geometry
occur, the PPS signal is no more available until the
minimum number of useful satellites is reacquired: in
these cases the image acquisition is driven by the odo
meter, which data can be also used to interpolate the
GPS positions. During the survey analogue images are
also recorded by a color camera: these images are used
in post-processing to extract all useful attributes, i.e.
qualitative features, of selected objects of interest. All
on board devices are controlled in real time via the
Gpslmage software, running on a PC Pentium III pro
vided with a 13 GB Hard Disk. This high capacity
allows up to 4 hours data recording, capturing two
digital images, each of 450 KB, every second.
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