International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B5, 2012 
XXII ISPRS Congress, 25 August - 01 September 2012, Melbourne, Australia 
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advantages of MLS data for producing high resolution 3D 
models are obvious, as is demonstrated by the examples later in 
this issue. 
Current version of the ROAMER, a single-scanner mobile 
mapping system for road environment mapping was 
internationally introduced in (Kukko et ah, 2007), and offers the 
possibility to use vertical or tilted scanning plane for adapting 
the system for appropriate 3D point acquisition in different 
tasks. In this paper a multiplatform approach used to operate the 
ROAMER, and a completely new backpack Akhka MLS system 
are described and discussed. Results from an evaluation of the 
ROAMER data accuracy against a permanent MLS test field are 
given, and an accuracy assessment of the Akhka data against 
implemented in situ target field method is performed. 
2. MULTIPLATFORM MLS 
ROAMER mobile laser scanning system of the Finnish geodetic 
Institute seen in Figure l is a high-end surveying device for 
producing accurate, dense and precise point clouds for three- 
dimensional detection, localization, modelling, analysis and 
monitoring of artificial and natural objects and processes. The 
initial goals for the system were to develop a system that would 
maximize the automation of feature extraction at the post 
processing phase (Kukko et al., 2007). Additionally, the system 
should be a moving laboratory flexible for various applications. 
Table 1 summarizes the current ROAMER equipment and the 
main data acquisition parameters that are operator selectable to 
adapt the data acquisition appropriately to the task at hand. 
FARO Photon 120 scanner 
■ 120-976 000 pts/s, user selectable 
■ 320 maximum field of view 
■ 3-61 Hz scan frequency , user selectable 
NovAtcl SPAN GPS-IMU 
■ NovAtel DL-4plus receiver and GPS-702 antenna, 
■ LI and L2 frequencies 
■ Honeywell HG1700 AG11 tactical-grade RLG IMU 
■ Gyro bias 1.0 deg/h 
■ Random walk 0.125 deg/rt-hr 
* Data rate 100 Hz 
Bi-trigger synchronization 
■ In-house built electronics 
■ Scanning start-stop 
■ Delivers scanner triggers to receiver log 
Table 1. ROAMER MLS system equipment and characteristics. 
ROAMER is a DC powered compact unit that can be installed 
on various carrier platforms for mobility and requirements set 
by application. Operation time of the system in battery power is 
several hours at a time, whereas in vehicles the DC output can 
be used as power source for continuous operation. Data 
recording computers are rugged laptops. 
The laser scanning unit in ROAMER is FARO Photon 120 that 
uses 785 nm laser with power of 20 mW (Laser class 3R). The 
scanner operates up to 976 kHz point measurement frequency 
and 61 Hz maximum profile measurement rate with 153 meter 
ambiguity interval of the phase-shift ranging. Laser beam 
diameter at the beam exit of the scanner is 3.3 mm and the beam 
spreads according to 0.16 mrad divergence angle. That results 
to laser footprint size of 20 mm at 100 m range from the scanner 
allowing together with the precise range measurement, detailed 
3D measurements from the objects. 
Figure 1. Left: ROAMER as a vehicle MLS (Photo courtesy 
Hannu Hyyppa). Right: Trolley MLS installation. 
2.1 ROAMER - Vehicle MLS for urban mapping 
Urban modelling is today a field of the most effort by the global 
enterprises pursuing for 3D data products. Mobile mapping is 
the only technology to offer the pedestrian point of view to the 
process with sufficient level of detail for personal navigation in 
mobile handheld devices as introduced e.g., in 3D-NAV1- 
EXPO project (Liu et al., 2010). Vehicle MLS is currently 
widely used in the context of urban area mapping, as the vehicle 
platform provides sufficient speed along with the traffic, and 
enough room for the equipment needed for the surveying. 
Vehicle MLS data from streets contain typically intensity 
information about road paintings and geometric information 
about buildings, bridges, pavement, pedestrian structures and 
islands, man holes, curbs, poles, signs and pylons, as seen in 
Figure 2. Intensity readings can be utilized in addition to the 
geometric information for automatic extraction of different 
target types from the point clouds (Jaakkola et al., 2008). 
Detection and inventory of utility poles, traffic sings and lamp 
posts is a good example of utilizing MLS in urban infrastructure 
maintenance as studied in (Lehtomaki et al., 2010). MLS data 
could also provide up-to-date information of power lines and 
other open air infrastructure, railway facilities etc. 
Figure 2. Vehicle MLS data from a street comer captures 
geometry of the streets, road paintings and other 
road environment structures in high detail. 
The scanning geometry and point density for a mobile lidar is 
different from the airborne laser scanning. For ROAMER the 
along-track profile spacing is shorter than 0.5 meter even for the 
speed up to 70-80 km/h when high mirror speeds are used. With 
61 Hz scan frequency the profile interval becomes better than 
20 cm when the speed is kept below 40 km/h, and still the point 
resolution along the profile is 15-30 mm, which is sufficient for 
the practical ranges of 20-40 m in the urban environment. In the 
end, the resulting point pattern cast on the scene depends on