v bundesamt für kartographie und geodäsie - DGK - Bayerische ...

Institute of Geodesy and Navigation – University of the Federal Armed Forces Munich 275
2.1.7 HIGAPS
Satellite-based navigation and positioning has already and
will have an ever increasing influence on our daily life in
the future. The trend converges in the U.S. Federal Communications
Commission’s E-911 mandate that requires network
carriers to provide location or geo-coding of
emergency callers who are using wireless handsets. Similar
activities of the European Commission under the E-112
initiative have led to a regulatory directive published in July
2003. On the other hand, the increasing demand for
commercial location-based services (LBS) has driven
cellular phone and network manufacturers to focus on
positioning solutions that are even more accurate than the
regulatory mandates.
Taken all this into account, an important step into the market
for Galileo is the in-time availability of large-scale integrated
combined Galileo/GPS receiver chipsets for consumer
applications. This is the main idea behind the
HIGAPS project – the development of a large-scale integrated
combined Galileo/GPS receiver chipsets for consumer
applications, preferably for pedestrian and vehicular
users. The HIGAPS project is a national funded project,
commonly funded by the Bavarian Ministry of Economic,
Transport, Infrastructure and Technology and the German
Space Agency DLR. The consortium is led by IfEN GmbH
and consists of Infineon Technologies AG in Munich, the
Fraunhofer Institute of Integrated Circuits in Erlangen, the
Institute of Geodesy and Navigation of the University FAF
Munich and the Department of Technical Electronics of the
University Erlangen-Nuremberg.
The Institute of Geodesy and Navigation focuses on the
development of high sensitivity GPS/Galileo acquisition
and tracking algorithms and on the development of navigation
algorithms optimized for operation in an urban or indoor
environment. GNSS navigation signals in these
environments can be strongly attenuated (about 25 dB), or
even blocked and are show intensive multipath effects. The
algorithms cope with these problems and are developed and
tested using the Institute of Geodesy and Navigation PCbased
experiment Software Receiver ipexSR.
2.2 Development of airborne gravimetry including
GNSS satellite observations
The detailed structure of the Earth’s gravity field and its
temporal variations is important for many scientific and
economic applications (e.g. geoid determination, geophysics,
exploration purposes). In order to guarantee this
wide field of use a measurement system for the determination
of this gravity data on the one hand should be accurate,
reliable and with a high resolution but an the other hand
also efficient and independent of the area of operation. In
comparison and in extension to satellite based and terrestrial
methods airborne gravimetry seems to be an optimal
solution to determine regional gravity variations. But current
airborne systems cannot meet the requirements of the most
users in accuracy and resolution caused by sensor errors.
Therefore in the scope of the project an airborne vector
gravimetry systems is in development using an existing
strapdown INS (Sagem Sigma 30) and precise GNSS
observations. The system errors influencing the gravity
anomalies should be reduced to achieve an accuracy of 1
mGal with an resolution of 1 km.
In order to reach this goal some investigations are carried
out concerning three different aspects: processing of INS
data with suitable alignment algorithms and precise modelling
of INS internal error sources, derivation of kinematic
accelerations using GNSS observations (inclusion of new
digital filters, differentiation methods, computation of
acceleration using also multi-antenna receivers) and the
determination of the gravity anomalies (possible smoothing
filters, calibration models using additional information like
ground control points). As in 2002 the theoretical background,
the implementation of possible data processing
methods and the development of the integrated sensor
system were in the centre of interest in 2003 and 2004 its
performance will be tested and evaluated in some practical
flight experiments also in comparison to other implementations
of airborne gravimetry systems.
These investigations are carried out within the scope of a
common research and development program of the German
federal ministry of education and research and the DFG
(Deutsche Forschungsgemeinschaft) called “Geotechnologien”.
The project described above is one part of the key
aspect “Investigation of the systems earth using (satellite
based) remote sensing methods”.
2.3 Integration of GNSS and INS measurements using
the tight coupling principle
In order to guarantee the user requirements in accuracy,
reliability and also integrity in a lot of applications integrated
GNSS/INS-system are used. Especially for navigation
purposes in most cases only the combination with lowcost
inertial measurement units with fiber-optic gyros or
MEMS-technology sensors are required to effect a sufficient
system performance, because its systematic errors can be
estimated using the technique of Kalman filtering. In
opposite to standard coupling implementations during this
project the tracking loops of a GNSS receiver should be
directly supported by inertial data (tight coupling). If the
receiver dynamics measured by the INS can be subtracted
from the satellite signal a decreased filter bandwidth allow
an increased receiver performance especially in an high
dynamic environment.
On the one hand an tight-coupling simulation tool was
implemented in order to evaluate mainly the required
performance of inertial data and possible feed-back effects.
On the other hand a practical test system for land navigation
was developed realising this coupling principle. Thereby
the signal processing of a GNSS receiver development tool
was modified in such a way, that calculated pseudorange
velocities and accelerations can be transferred directly into
the receiver tracking loops. A significant reduction of
satellite reacquisition time and a clear increase in tracking
loop stability could be verified.