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AN INTELLIGENT MOBILE MAPPING SYSTEM
Naser El-Sheimy, Mike Chapman, and C. Tao
Geomatics Engineering Department
The University of Calgary, Canada
Tel: (403) 220-7587 - Fax: (403) 284 1980
E-mail: naser@ensu.ucalgarv.ca
KEY WORDS: Mobile Mapping Systems, GPS/INS Integration, CCD Cameras, georeferencing, Expert Knowledge
Systems, Quality Control, INS Bridging.
ABSTRACT
Mobile Mapping Systems (MMS) are an emerging trend in Geomatics because they allow a task-oriented implementation
of geodetic concepts at the measurement level. This trend towards MSS in mapping and GIS application is fueled by the
demand for fast and cost-effective data acquisition system. The selection of sensors for such data acquisition system
obviously depends on system requirements, such as accuracy, reliability, operational flexibility, range of applications and
on technological developments which allow to satisfy this demand. In general, the data acquisition module contains
imaging sensors and navigation sensors. Navigation sensors are used to solve the georeferencing problem. Although a
number of different systems are used in general navigation, the rather stringent requirements in terms of accuracy and
environment make the integration of an inertial navigation system (INS) with receivers of the Global Positioning System
(GPS) the core of any sensor combination for an accurate MMS. To achieve consistent accuracy with an integrated
GPS/INS under different operational environment, quality control is a must. Since the required accuracy can usually be
achieved for good satellite coverage and signal reception, the expert knowledge system is mainly concerned with cases of
poor GPS satellite geometry, signal blockage, or cycle slips, and the role of INS aiding in fixing these problems. In a
commercial environment, the production cost is a significant factor to take into account. The expert knowledge system
optimizes the survey methodology to increase the productivity of a MMS.
The expert knowledge system, therefore, should have a real-time and a post-mission component. In real time, one wants
to decide whether a specific set of data is sufficient to provide the required accuracy with a certain level of probability. In
post mission, one wants to analyze the result and performance achieved in different environment to increase the
knowledge base of the system. This paper will introduce the expert knowledge developed for the VISAT (Video-INS-
SATellite) MMS. This will include the calibration module, the planning of the survey, the definition of essential
parameters for accepting an INS ZUPT, the use of INS data for bridging GPS outages, the use of backward smoothing
procedures and OTF ambiguity resolution. All major features will be illustrated by examples from field tests. Finally, data
flow optimization and the potential for automation of the data acquisition using the expert knowledge will be reviewed
with a view to the idea of developing intelligent mobile mapping systems.
1. THE TREND TOWARD MOBILE MAPPING
SYSTEMS IN MAPPING APPLICATIONS
Mobile Mapping Systems (MMS) have become an
emerging trend in mapping applications because they allow
a task-oriented implementation of geodetic concepts at the
measurement level (Schwarz and El-Sheimy, 1996).
Examples of such systems can be found in airborne remote
sensing (Cosandier et. al. (1994) and Seige (1994)),
airborne gravimetry (Wei and Schwarz (1995), airborne
laser scanning (Wagner (1995)), and mobile mapping from
vans and trains (Lapucha (1990), El-Sheimy and Schwarz
(1995), and Blaho and Toth (1995)). All of these systems
have a common feature in that the sensors necessary to
solve a specific problem are mounted on a common
platform. By synchronizing the data streams accurately, the
solution of a specific problem is possible by using data
from one integrated measurement process only. The post
mission integration of results from a number of disjoint
measurements processes and the unavoidable errors
inherent in such a process are avoided. This results in
greater conceptual clarity, task-oriented system design and
data flow optimization, and also offers in most cases the
potential for real-time solution, which is becoming more
important in many applications.
The trend towards MMS in geomatics is fuelled by the
demand for fast and cost-effective data acquisition and by
technological developments which satisfies this demand.
Two developments are especially important in this context:
Digital imaging and precise navigation. Digital imaging
