903 
RESEARCH ON POSITIONING AND POSING OF MOBILE MAPPING IN 
METROPOLIS 
Wang Weian 3 *, Ou Jianliang 3 , Bao Feng a , Tong Xiaohua 3 , Liu Chun a , Ye Qin a , Wang Jianmei 3 , Wang Wei 3 , Liu Meiyu 3 , Liu Yi a , Liu 
Shijie 3 , Wu Hangbin 3 , Qiao Gang 3 , Zheng Zheng 3 
a Dept, of Surveying and Geo-informatics Engineering, Tongji University, 1239 Siping Rd., Shanghai, China, 200092 
WG ICWG V/I - Integrated Systems for Mobile Mapping 
KEY WORDS: Mobile mapping, GPS Doppler measurement, Dynamic characteristic analysis, Network RTK, Position data 
filtering 
ABSTRACT: 
Mobile mapping, a revolutionary surveying and mapping technology with multi-sensor and 3S (GPS, GIS and RS) integration, is a 
typical approach to satisfy the upcoming demand for efficient data capture and updating of geo-spatial data in traditional methods 
limited situation. The positioning and posing sub-system provides direct georeferencing for mobile mapping. The issue on how to 
ensure the positioning accuracy in metropolis is highlighted. Generally, it is solved by integration with differential GPS and INS/DR. 
Another side, network RTK has more advantages such as real-time data processing, no base and no working range limitation, is more 
suitable for city mobile mapping, but its signals are significantly affected by city environment. The paper presents a solution to filter 
the network RTK dynamic positioning data, and improve the ability and reliability for mobile mapping direct georeferencing. We 
analyzed city mobile platform’s positioning data in different GPS modes, including DGPS, network RTK, and got the dynamic 
characteristics. GPS Doppler measurement provides cm/s level 3D speed even in single GPS mode without the requirement of GPS 
ambiguity issue in 0.1s interval, then used to filter rude data in network RTK Is interval positioning data. Experiments were 
performed with the mobile mapping field work in Yan’an Road of Shanghai, which involves overhead mainlines, viaducts, 
skyscrapers, and other typical city characteristics. The filter results proved that this filter method is effective in extinguishing errors 
in dynamic network RTK data and improving the reliability of mobile mapping positioning data. 
1. INTRODUCTION 
Mobile mapping technology has been researched and developed 
since the late 1980s. The original use of mobile mapping is for 
highway infrastructure management and transportation 
inventory (Li, 1997). With the civilian use of GPS technology, 
its continuous positioning and posing was settled by GPS and 
INS (inertial navigation system) or DR (dead reckoning) for the 
mobile track and then gave the DG (direct georefenencing) 
capability (Schwarz, 1993) to each spatial observing data, such 
as CCD image, laser scanning and etc. The mobile mapping 
system is capable of providing an absolute positioning accuracy 
of 0.3m and a relative accuracy of 0.1m for object points within 
a 30-m corridor, at vehicle speeds of 50-60 km/h (Li et al., 
1994; Tao, 1999). Mobile mapping is one of the typical survey 
technology of the 3S (GPS, RS, GIS) integration and multi 
sensor fusion (Li, 1997; GreJner et al., 2004). Now it is more 
and more widely applied in large-scale mapping (1:2000, or 
even larger scale) with no requirement on ground control points, 
and GIS database updating. Its outstanding advantages are high 
efficiency (field survey with the mobile platform speed as 60 
km/h) and low cost (only 1/4 or even lower compared to 
traditional method) (Li, 2006). 
The positioning and posing sub-system, which is a core part of 
MMS, provides MMS direct georeferencing for standalone 
surveying. The reliability and accuracy plays a very important 
role in MMS. How to improve positioning and posing 
capability, especially in the complicated circumstances of 
metropolis, is a highlighted issue. Mobile platform’s un 
interrupt track acquisition comes from GPS constraint and 
INS/DR’s connection while GPS out of service (Li, 1997). 
Track accuracy is mainly influenced by the blocked span of 
GPS signal and weak GPS positioning ability in complicated 
city region, such as surrounded by overhead road, high 
buildings, crossing viaduct, tunnel and etc. 
According to data-capture methods, the GPS data process mode 
can be classified as Differential GPS (DGPS), Real Time 
Kinetic (RTK), and network Real-Time Kinetic (network RTK) 
(Wang, 2001). In them, DGPS has three characteristics: a stable 
base station is required, data is post processed, and the working 
range is limited to 30 kilometres. RTK, besides real-time data 
processing and a 10-kilometer working range limitation, a 
stable base station which can emit radio signals to the MMT 
platform is used. Similar to RTK, network RTK also has the 
advantage of real-time data processing, yet it has no working 
range limitation while the base-stations’ network is built in the 
whole area, for example, the whole region of Shanghai has been 
covered by 7 base-stations (Ji, 2007). Totally, network RTK is 
superior to the other two methods when MMS is working in 
areas such as the big cities where are covered by the base- 
stations’ network. However, the radio signals sent out from base 
station may be significantly affected by the environment factors 
in urban areas. There are problems such as signal sheltering and 
multi-path caused by complex constructions just as the forest of 
city skyscrapers and overhead bridges. In general, network 
RTK need several seconds to get a steady solution for certain 
position, but land-based mobile mapping always works as a 
certain moving speed. DGPS can receive data in time interval of 
*Wang Weian, e-mail: weian@mail.tongji.edu.cn; phone 86-21-65985212; fax: 86-21-65981085