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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