LASER SCANNING AND ITS POTENTIAL TO SUPPORT
3D PANORAMIC RECORDING
A. Wehr

Institute of Navigation, University Stuttgart, Breitscheidstr. 2, 70174 Stuttgart, Germany - wehr@nav.uni-stuttgart.deCommission VI, WG VI/4
KEY WORDS: Laser Scanning, 3D-Panoramic Recording, Ranging Principles, Moving Platform
ABSTRACT:
Today very fast terrestrial laser scanners are available which can be very well combined with panoramic cameras to make 3Dpanoramic recording possible. Due to the very precise depth information of the laser scanner and the high resolved color information
provided by the CCD sensor of the panoramic camera 3D-panoramic images of high quality can be obtained. In order to assess theperformance of such integrated systems, this presentation gives a short introduction in the ranging principles applied in terrestrial
laser scanning. Commercially available terrestrial laser scanners using the measurement principles applicable for panoramic
mapping will be presented. Their technical parameters will be discussed with regard to range, angular and depth resolution. Also the
problem of moving panoramic mapping will be addressed.
1. INTRODUCTION
In recent years very fast and precise terrestrial laser scanners
with ranging capabilities of up to more than 100 m (Fröhlich,2004) have been developed. These devices offer very precise
depth information with high point densities and sampling rates
of up to 600 kHz, however deliver in many cases poor intensity
images compared with cameras. Some laser scanners obtain an
intensity image by detecting the intensity of the backscatteredlaser light (Fröhlich 2004, Wehr 1999). This results inmonochromatic images. If color information is required
additional sensors or CCD cameras must be implemented.
Besides CCD array sensors possible optical sensors for color
images are panoramic cameras. Panoramic cameras are realizedby turning azimuthally a vertical CCD-line with accessory
optic. Panoramic laser scanners scan their surroundings with avertical line scan and turn the sensor head like the panoramic
camera. As both systems feature identical surveying geometries
the combination of laser scanners with panoramic cameras is alogical consequence.

dynamic they are not well suited for panoramic mapping andwill not be regarded in the following.
Higher range dynamic can be achieved by radar measurement
principles. Ranging by radar means is basically a time-of-flightmeasurement. As lasers produce short pulses with very highpeak power pulse laser ranging is commonly used. Here thetravelling time of the laser pulse is measured. Anotherpossibility to determine the travelling time of a signal isrealized by measuring the phase difference between thetransmitted and received signal. Both methods are going to be
explained and their performance will be discussed in thefollowing.
2.1 Pulse Ranging
Carrying out ranging by measuring the travelling time of a shortlaser pulse from the laser aperture to the target surface and backThis presentation gives a short introduction in the ranging
principles applied in terrestrial laser scanning. Commerciallyavailable terrestrial laser scanners using the measurement
principles applicable for panoramic mapping will be presented
and their technical parameters will be discussed with regard torange, angular and depth resolution. Also the problem ofmoving panoramic mapping will be addressed.
2. RANGING PRINCIPLESIn terrestrial laser scanning ranging is carried out either bytriangulation or by measuring the time of flight of the laser
signal. The triangulation measurement principle is applied forlaser scanners with low depth dynamic. In close range
applications of e.g. up to 5 m accuracy better than 1 mm arepossible. Such scanners are produced by Mensi and Minolta.
Due to the very limited range performance and ranging

Figure 1. Pulse ranging
to the receiver (two way ranging) is the typical laser ranging
method. It makes optimum use of the laser transmitter which
has the capability to generate very short pulses with very highpeak power levels with high repetition rates. The pulse length
TP determines the ranging resolution ∆R and the ranging
accuracy σR (s. Figure 1). The range resolution ∆R tells how far

apart two targets have to be, so that they can be resolved as twotargets. The power loss of the received signal determines the
maximum possible range. Range resolution ∆R and accuracy σR
are calculated by

∆R =

c
2
c

σR =

2

⋅T
P
⋅

(1)

TP
SNR

(2)

where c is the speed of light and SNR is the signal-to-noise
ratio. The resolution of the range measurement ∆s is determinedby the resolution of the time interval counter ∆tL:∆s =c

⋅ ∆t L(3)2∆s is generally lower than ∆R and may not be mixed up with it.

σR =

λ
1
⋅
4π SNR(5)

This method can be easily realised with semiconductor laser
diodes, because here the intensity of the light can be directly
modulated by the drive current. Due to the high electrical
bandwidth of the laser diodes high frequencies up to more than
10 GHz are possible. However, the available cw-power is very
limited. Therefore, the ranging method of measuring the phasedifference is primarily applied in near range scanning systems.
In contrast to pulse laser systems single targets within the laser
beam cannot be resolved. Therefore, ∆R is not defined. The
receiver detects only the resultant phase of all returns. As themodulation signals are recovered by synchronous demodulation
techniques, the intensity of the backscattered laser light can bedetected without disturbing background radiation. This meansthat these systems are very robust against high backgroundradiation, e.g. sun light and external illumination.

2.2 CW-Ranging by Measuring the Phase Difference

In continuous wave (cw) laser ranging the laser intensity is
modulated with a well defined function, e.g. a sinusoidal or asquare wave signal. The modulation signal is repeatedcontinuously with period time TPd. The laser emits light
continuously with moderate average power levels and therefore
is called cw-laser. The time of flight of the signal TL isdetermined by measuring the phase difference between thetransmitted and received signal. The period time TPd or its
equivalents the frequency f or wavelength λ defines the

3. SCANNING PRINCIPLESIn order to obtain 3D-information of the surface of an object thelaser beam and the receiving optical path have to be moved
across the surface by a certain scanning pattern. Knowing foreach sample the slant range and the instantaneous direction of
the laser beam the 3D-coordinates can be computed.
Accordingly to Figure 3 the instantaneous field of view (IFOV)
is determined by the divergence of the laser beam and the fieldof view (FOV) defines the sampled area. For scanning the
IFOV various opto-mechanical deflection systems can beapplied. They are selected in dependence of the application.
Typical scanner drives are stepping motors, brushless dc motors
and linear drives mostly in the form of galvanometer scanners.
Table 1 presents a compilation of scanners applied in terrestrial
laser scanning.

Figure 2. Phase difference
maximum unambiguous range Run, which is λ/2 for two-way
ranging, and the range resolution ∆s. For a given phaseresolution ∆θ, the range resolution ∆s is calculated by
∆s =

λ
2

⋅ ∆θ

Figure 3. Main components of laser scanners(4)

Formula 4 shows, that the range resolution can be easily
improved by using signals with shorter wavelengths if the phaseresolution is kept constant. However, shorter wavelengths mean
reduced maximum unambiguous ranges. Therefore, satisfying
ranging capabilities with high range resolution are only possible
if several modulation signals with different frequencies areapplied. Such method is also known as multi-tone-ranging or
multi-frequency-ranging. Here the highest frequency
determines the resolution and the achievable accuracy and thelowest frequency the unambiguous range. The accuracy σR isdetermined by

For imaging systems two galvanometer scanners are arranged
orthogonally to each other. But also a combination of apolygonal scanner and a galvanometer are possible. Here thepolygonal mirror carries out the fast scan. For hemispherical
coverage a fast vertical line scan in combination with anazimuth rotation of the total opto-mechanical head is applied.
The fast vertical line can be realized with e.g. galvanometerscanners, polygon scanners or a shaft scanner. The azimuth
rotation requires powerful drives with very precise bearings.
Either steppers or motors with gears can be applied. Using
analogue motors an angular encoder is required.

Principle

Name
Galvanometer Scanner
Scanning speed dependenton mirror inertia. Max.
scanning rate: 5 kHz, max.
FOV ±45 deg
Application: Imaging laser
scanner
Polygonal Scanner
Typical drive for fast line
scans. If one rotation
direction is possible very
fast scans can be obtained.
Speed up to 40000 rpm

z

Shaft Scanner
Typical drive for profile
scanners. Very fast scanspossible. Often applied forhemisphericalscanning.
Speed up to 40000 rpm

Table 1. Different scanning devices
Which scanning mechanism is optimum, is very dependent on
the application, the size of the optics and required FOV. The
goal for every scanning device is to be as fast as possible. The
scanning speed is determined by the inertia of the device to be
moved. This means e.g. the optics should be as small as
possible. However, small optics mean a reduction in received
energy and by that a reduction in range. This discussion makes
clear that the design of scanners is a result of an engineering
trade-off. One can conclude generally, if an oscillating
movement of the sampling beam is not required either
polygonal scanner or shaft scanner are an optimum choice.

systems is very limited. The panoramic cameras can be groupedin:1.
cameras, where the camera body is turned in azimuth
and2.
fixed mounted cameras, which use either special
refracting or reflecting optics, which allow ahemispherical coverage.
For the first panoramic recording principle either CCD arrays or
CCD line sensors are applied. If very high resolved panoramic
images are required a CCD line containing e.g. 10000 pixels isused (s. Figure 4), which is mounted on a turntable parallel tothe rotation direction with a resolution of about 65000 pixels.
Moving the turntable generates the second image direction.
According to Figure 5 the surveyed points are imaged on acylinder. The radius of the cylinder is given by the focal lengthof the optic. Manufacturers of panoramic cameras using thisprinciple are KST Dresden and JointMetriX. The typicaltechnical data of the EYESCAN panoramic camera arecompiled in Table 2.
Number of Pixel
3*10200 (RGB)Radiometric
14 bit / 8 bit per channel
dynamic/resolution
Shutter speed
4ms up to infinite
Data rate
15 Mbytes / sData volume 360° (optics 3Gbytes
f=60mm)Acquisition time
4 minPower supply
12 V
Table 2. Technical parameter of the digital panoramic camera
As shown in Figure 4 the sensor system consists of the camera
head, the optical and the high precision turntable with DC-gearsystem motor. The objective can be changed in accordance tothe application. The camera head is mounted on a tilt unit forvertical tilts of ±30° with 15° stops. Axis of tilt and rotation are

4. PANORAMIC CAMERASZ

Before laser scanners are selected which are suitable forpanoramic mapping, a closer look to panoramic cameras has tobe taken. Searching the commercial market for digital
panoramic cameras makes clear that the number of available

Object Space

X

Y
rxy
k

X

CCD-Linec

CameraObjective

X'

Figure 5. Sampling geometry of CCD-line panoramic
camerain the needlepoint. The cameras of the second group are
realized with state-of-the-art CCD-arrays with 1280 x 1024
pixels. The hemispherical view is achieved either by an extreme
wide angle optic (s. Figure 6, left) or with a special mirror in
front of a standard optic (s. Figure 6, right). The extreme wide
angle optic is used by Sony. The advantages of these cameras
are, that no moving parts are used but the poor resolution is
disadvantageous and the optics may exhibit aberrations.
Figure 4. CCD-line panoramic camera

units are implemented. To make a comparison easier the slant
range accuracy is related to 25 m for all scanners.
mirrorLaser Scanner

lens

CCD arraydiffracting optic

camera
optic

CCD arrayreflecting optic

Figure 6. Panoramic camera with CCD-array

5. LASER SCANNERS FOR PANORAMIC MAPPING

Up to date only panoramic cameras which have CCD-line
sensors are used if they are applied for surveying, This kind ofcamera has got the required accuracy for this purpose and themeasurement results can be processed by photogrammetricevaluation means. As these cameras image a vertical line at theobject and this line is rotated in azimuth, it is obvious to use
laser scanners having the same sampling geometry, if laser
scanners and panoramic cameras should be used in combinationto achieve 3D panoramic recording. Therefore, in the following
only this kind of lasers will be regarded.
In accordance to Table 1, fast vertical scans can be realizedwith e.g. polygonal mirrors or the rotating shaft. The second
dimension is realized by a rotation of the whole optomechanical head. Possible commercial laser scanners are:iQsun 3D Laserscanners of iQvolution, Imager 5003 of Zoller& Fröhlich, the HDS series of Leica and the LSM series of
Riegl.
In the following it will be studied, how the performance of 3D
laser scanners may support high definition image recording toobtain 3D-panoramic surveys.
5.1 FOV and Resolution

In this chapter the FOV, the resolution in the object space andthe surveying time will be compared. Most available scanners
cover ranges of 20 m or 50 m respectively. This satisfies theneeds for many indoor measurements and even for some
outdoor surveys. Up to now only laser scanners using the pulse
measurement technique reach ranges of up to several hundred
meters (s. Table 3, part 1). In Table1 the relevant data for theevaluation are compiled. Here Rmax is the maximum range andfsamp is the sampling rate for one pixel. The standard deviationof the measured slant range σ is related to 25 m. The angularresolution of the scanners is separated in azimuth (horiz.) andvertical (vert.) direction. Leica does not show angularresolutions in their data sheets. It is obvious that the scanners of
the Riegl company perform vertical scan with a field of only
90 deg or 80 deg respectively. The reason for this is that ascanning drive with a polygonal mirror is used. The table makes
clear that the laser scanners of the companies Zoller&Fröhlich,
iQsun and Leica show the best accuracy. However, they are
limited in range, because all work by the measurement principleof measuring the phase difference. In the Riegl systems pulsed

FOV [deg] Rmax
vert. horiz. [m]

fsamp
σ25m
[kHz] [mm]Zoller&Fröhlich
LARA25200 310
360
25.2 625
4,5
LARA53500 310
360
53.5 500
9iQsun 880HF40
320
360
40
120
3
320
360
80
120
3
Leica
HDS 4500 310
360
25
500
7
310
360
53.5 500
11
Riegl
LMS-Z360i 90
360
60
12
12
LMS-Z420i 90
360
250
12
10
LMS-Z210i 80
360
120
12
25
Table 3. Performance of typical laser scanners (part 1)
Laser∆φ [deg]
Scannervert. horiz.
Z&F
LARA25200 0.018 0.018
LARA53500 0.018 0.01
iQsun
880HF400.01 0.0008
0.01 0.0008
Leica
HDS 4500 --------Riegl
LMS-Z360i 0.01 0.01
& Z210i & 0.01 0.01
Z420i

LMS-Z420i 0.01

0.01

∆s [mm]vert. horiz

8
16

8
9

@25 m
@50 m

4
9

0.35
0.7

@25 m
@50 m

-----

@25 m
@50 m

----4
8

4
8

@25 m
@50 m

44

44

@250 mTable 3. Performance of typical laser scanners (part 2)
In order to make the evaluation clearer the resolution on theobject ∆s in a slant range distance of 25 m and 50 m is
calculated from the angular resolution ∆φ in Table 3, part2.
5.2 FOV and Resolution of Panoramic Camera

In order to study if laser scanners can support 3D panoramic
mapping a similar table with key performance data is set-up for
the CCD-line panoramic camera Eyescan M3 Metric built by
KST Dresden. The technical data of this camera are compiled inTable 2. The camera can be used with different objectives. The
following focal lengths f are available:
35 mm, 50 mm, 60 mm and 100 mm
Knowing the length l of the CCD-line which is 72 mm and thenumber of pixels on the CCD the vertical FOV can becalculated by⎛ l ⎞⎟⎝2⋅f ⎠

FOV = 2 ⋅ arctan⎜

and the vertical resolution ∆φ can be computed by
FOV
∆ϕ =
N

(6)

(7)

where N is the number of pixels of the CCD-line which is
10000 (s. Table 1). The horizontal angular resolution isdetermined by the azimuth drive and is independent of theobjective. The standard step width is 0.008 deg. This means in
25 m and 50 m distances the following horizontal resolution on
the object’s surface can be calculated:

if FOV is the vertical field of view, ∆φvert the vertical angularresolution and fsampl the measurement rate for each pixel. For
the Zoller&Fröhlich and iQsun laser scanners the FOV wasdetermined with 360 deg, because here shaft scanners are usedwhich rotate with constant speed over 360 deg. The Riegl
scanners are realized with polygonal scanners which have a
FOV of 90 deg. Therefore, in this case FOV equals 90 deg.

∆sH(25 m) = 3.2 mm, ∆sH(50 m) = 7.2 mm
Laser Scanner

In Table 4 the angular vertical resolution ∆φ and the resolution
on the object´s surface ∆sV are compiled in dependence on the
focal length.

Zoller&Fröhlich
LARA25200 29 msec
17.4 min
LARA53500 36 msec
21.6 miniQsun 880HF40
300 msec 180 min
300 msec 180 min
Riegl
LMS-Z360i 750 msec 450 min
LMS-Z420i 750 msec 450 min
LMS-Z210i 667 msec 400 min
Table 5. Scanning times of laser scanners

f
FOV
∆φ
∆sV @ 25 m ∆sV @ 25 m
[mm] [deg]
[deg]
[mm]
[mm]
35
92
0.009
4
8
50
72
0.007
3
6
60
62
0.006
2.6
5
100
40
0.004
1.7
3.5
Table 4. Vertical resolution of panoramic camera

Assuming the line of sight of the camera is aligned horizontallythe heights compiled in Table 5 can be surveyed.
fh @ 25 m
h @ 50 m
[mm]
[m]
[m]
35
18
36
50
14.6
29
60
13
26
100
8.6
17
Table 4. Heights above ground
5.3

The fastest laser scanner needs already 29 msec for the total
vertical FOV of 310 deg (s. Table 5). With regard to Table 5 theRiegl scanners require the longest vertical scanning time which
is 750 ms. The Riegl scanners are designed for much higher
scanning rates which is 20 scans per sec. However, this cannot
be achieved with a resolution of 0.01 deg. The vertical scanning
time determines directly the horizontal scanning time thoriz
which ist horiz =Performance comparison of laser scanners andpanoramic cameras

To carry out the comparison between laser scanners andpanoramic cameras, first the angular resolution in elevation isregarded. The discussion is based on the wide angle objectivewith a FOV of 92 deg. This comes closest to the field of view ofthe panoramic scanners which either perform 310 deg or
90 deg. However, having a vertical FOV of 90 deg means, thatan extra survey has to be carried out with an additional
elevation to obtain a full hemispherical coverage. Neverthelessthe comparison is realised with FOV of 90 deg. In accordance
to Table 4 the panoramic camera offers a vertical angularresolution of 0.009 deg whereas the laser scanners perform
about 0.01 deg (s. Table 3, part 2). The resolution in azimuth isgiven with 0.008 deg for the panoramic cameras and varies
between 0.0008 deg and 0.01 deg for the laser scanners (s.
Table 3, part 2). The very high resolution of 0.0008 deg is only
mentioned for the laser scanners of iQsun. So it seems that
0.01 deg is the more practical and realistic standard. It can beseen that both systems fit together very well with regard to theirangular resolution.
Now, the surveying time is going to be looked at. The
panoramic camera samples the vertical FOV in 4 msec. This is
the shortest time possible and requires a very good illuminationof the target. The values in Table 5 are calculated under theassumption that the horizontal and vertical resolution are
0.01 deg. Then the scanning time for one vertical line can becomputed byt sc =

FOV
∆ϕ

vert

⋅ fsampl(8)

Sanning Timevert.
horiz.

360 deg∆ϕ horiz⋅ t sc(9)

Based on equation 9, the calculated results are compiled inTable 5, which makes clear that the surveying time easily
reaches several hours.
As the panoramic camera exhibits a vertical sampling rate of
4 msec, a total panorama is surveyed in 2.5 min with ahorizontal angular resolution of 0.01 deg. The sampling rate of
4 msec is only possible with optimum illumination, this meansvery bright sunlight. Especially in rooms much longer sampling
rates are required. In our experiments with the M3metriccamera typical sampling rates were between 25 ms and 50 ms.
This means a total panorama takes about 15 min to 30 min.
This performance comparison clarifies that panoramic cameras
and laser scanners may work very well together. Especially thelaser scanners of Zoller&Fröhlich show comparable surveying
times. However, also the other scanning systems compiled inTable 3 can well be applied together with panoramic cameras toachieve 3D-panoramic recording.
6.

INTEGRATING LASER SCANNER AND DIGITALPANORAMIC CAMERASIn chapter 5 it was worked out, that laser scanners and digitalline scan panorama cameras have comparable surveying
geometry and sampling performance. The main advantage ofthe panoramic camera is the very short measurement time.
However, this time is dependent on the illumination of thetarget. Laser scanners are active measurement devices with theirown illumination source and therefore independent on external

light. At this point the engineering problem becomes obvious
combining a passively working system with an active one.
Nevertheless before integrating both surveying systems in asingle device several surveys were accomplished where thesame scene was sampled independently by a panoramic camera
and a laser scanner. Only the recording point of views wereidentical. Very impressive and promising results are publishedby (Abmayr, 2004). Here a digital panoramic camera and alaser scanner of Zoller&Fröhlich were mounted on the same
tripod. In this setup it was ensured that the location of thecamera’s optical center was almost identical with those of thescanner unit. In addition both devices were adjusted to eachother so that both horizontal rotation axes were aligned inparallel. Due to the special set-up only a simple co-ordinatetransform regarding the instantaneous horizontal rotation angle
was required. This simple calculation satisfies the needs of ademonstration. Further studies concerning the accuracy in
combining laser scanner data with panoramic camera data werecarried out by (Reulke, 2003 and 2004). In these references thenecessary processing steps for a quantitative analysis arepresented.
These experimental results lead to the idea to integrate CCDline and laser scanner in one device. A first possible solution isoffered by Riegl with its laser scanners LMS-Z360i and LMSZ420i. Here either a Nikon D100 with 3008 x 2000 pixels or a
Canon EOS 1Ds MARK II with 4992 x 3328 pixels supports
the survey. However, these cameras have got array sensors.
Therefore, imaging geometry differs. Optimum with respect tothe surveying geometry will be a solution with a CCD-line
sensor.

CCD-line camera, laser scanner and position and orientation
system.

Figure 8. Experimental MMS
The position and orientation system (POS) can be realized withan inertial measurement unit (IMU) which measures theinstantaneous orientation angles. The instantaneous position is
primarily determined by differential GPS using the carrier
phase and the lateral accelerations are measured by IMU. To
obtain valid surveying results the three systems must be
synchronized very precisely. A possible synchronization isshown in Figure 7. Figure 8 presents a realization of this mobile
mapping system (MMS). This unit was used for verification
tests.

7. MOBILE MAPPINGThe very emerging market for realistic 3D city models requires
new advanced sensors capable to provide high definition image
and depth data. Surveying e.g. total streets lined with housescannot be carried out with a static panorama survey as
discussed in the previous chapters. This application demands
mobile surveying platforms. The additional feature of mobility
means, that for each measurement point the instantaneous
position and orientation of the sensor system must be measured.
Knowing the position in a geographical co-ordinate system andthe exterior orientation the surveyed data can be geocoded. In
this chapter a feasibility assessment will be accomplished witha mobile mapping system comprising the following devices:
3D-LS

POS

GPS ANTENNAIMUEvent Marker 2

Panoramic Camera

Event Marker 1

Figure 7. Mobile mapping system and synchronization

7.1 Feasibility Assessment

In a first approach the geometrical parameters are studied. The
analysis is based on the typical system parameters presented inchapters 4 and 5. Table 4 already clarifies that panoramic
cameras may be used for gathering data for city models.
Optimizing the line of sight of panoramic cameras the front ofhouses with a height of about 30 m can be surveyed already in a
distance of 7.5 m, assuming the camera is mounted 2 m above
ground and looks with an elevation angle of 30 deg. The laser
scanners with a vertical FOV of 310 deg do not have to be
adjusted. However, going close to the objects with a very large
FOV means very flat incident angles. In this case it would be anangle of 75 deg measured from the normal of the object's
surface. The required FOV is not critical. In a second step
specifications for POS will be derived. In the following atypical angular resolution of 0.01 deg in horizontal and verticaldirection is assumed for imaging and ranging sensors. If theresolution of the sensors should not be degraded by POS, arequired angular accuracy of 0.001 deg should be achieved by
POS. As discussed by (Reulke, 2004) angular accuracy of
0.008 deg is achievable with high precision commercial POS.
This value is chosen for further calculations. Using this valuemeans already a degradation of the system performance,
because the accuracy of POS is very close to the resolution of
the camera. However, in near range mobile mapping theposition is much more critical. This fact is studied by thefollowing formula:∆p perm ≤(22∆s perm − D ⋅ ∆α 2 + ∆γ 2

)

(10)

∆pperm is the permissible lateral error of POS, D the distance tothe target, ∆α the angular resolution of sensor either panoramic
camera or laser scanner, ∆γ the angular resolution of POS and∆sperm the total permissible error. If ∆α and ∆γ are equal and aredetermined to 0.01 deg, equation (10) becomes:∆p perm ≤22 ⎛∆s perm − D ⋅ ⎜π⎝ 180 deg⎞⎠

⋅ 2 ⋅ 0.01 deg ⎟2(11)Permissible Lat. Error in [mm]This formula is evaluated as a function of distance D with∆sperm = 50 mm in Figure 9. This figure shows that thepermissible lateral error is primarily determined by the position
accuracy in close range. If distance D increases the permissible
lateral error for the position ∆pperm decreases, because angularerrors predominate. In case of POS-AV of Applanix theinstantaneous position is primarily determined by the GPS.
Even using differential GPS with carrier phase measurement

only a speed of 4.5 km/h. Driving with 50 km/h a vertical line
will be sampled every 5.6 cm. This means that the horizontal
resolution is one tenth of the vertical one. Preferable is an equal
resolution in both directions. As the exposure time cannot be
reduced, the sensor is oversized in vertical direction. The laser
scanners can be adapted better to this application, because thenumber of samples along a scan and the scanning speed areprogrammable.

Figure 10. Original scanned data with panoramic camera

60
50
40
30
20
10
0
0

50

100

150

200

Distance D in [m]Figure 9. Permissible lateral error
errors of at least 10 cm must be expected. It is obvious, in thisapplication the position determination is critical. First
experiments with POS-AV and a panoramic camera show very
promising results (Reulke, 2003). A heraldic animal at Schloß
Solitude in Stuttgart was surveyed. The object is hardly
recognizable (s. Figure 10) from the original camera data.
However, after correcting the data a high quality image is
obtained. The zoomed in part in Figure 11 illustrates the highcamera performance and depicts that the position determinationmust be much better than 10 cm, because the heraldic sign iswell resolved in detail. The higher accuracy is possible, due tothe joint post processing of IMU-data and GPS-data withspecial Kalman filters. Further experiments indicate, that GPS
reception is very degraded close to houses or in narrow streets.
This means some surveys failed because of GPS. Herealternative devices for position determination are desired.

Figure 11. Result after correction
With regard to reduced resolution the application of CCDarrays should be considered. For example the Canon EOS 10s
MARKII with 4992 x 3328 pixels offers the required resolution.
Due to the larger horizontal FOV the rate of the images is much
lower than line scan rate of the CCD-line camera. For instancewith a horizontal FOV of 30 m, an image rate of 1 image/sec
and an exposure every 15 m, a driving speed of 50 km/h ispossible.

To study the possible precision of a slow moving platform
camera and laser scanner were mounted on a robot (s.
Figure 12). Here the position and orientation was measured by
ARTtrack2. Therefore special tracking targets were mounted on
top. Here the position was measured with mm accuracy.
Another important parameter for mobile mapping is the
maximum possible velocity of the surveying platform.
Assuming the recording system moves parallel to a wall at a
distance of e.g. 30 m and each 5 mm a sample is taken invertical direction with angular resolution of 0.01 deg. If thespacing in horizontal direction - this means in the direction theplatform is moving - should be equal, the maximum possible
speed is 1.25 m/sec, if the exposure time is 1/250 sec. This is

Figure 12. Mobile robot platform

8. CONCLUSIONSIn this paper the survey of commercially available laser
scanners proves that these devices can be well combined withdigital panoramic cameras using CCD-line sensor. First, both
systems have the same surveying geometry and secondly themeasurement rate and the resolution are in the same order ofmagnitude. First experiments with an integrated set-up
demonstrated the feasibility to obtain high definition colour 3D
panoramas. The tests confirm that the depth accuracy satisfies
the envisage applications. However, more quantitative studies
must be carried out in the future. Though the experiments lookvery promising, one has to take into account that a passive
sensor is used in combination with an active one. Therefore, theadvantage of the active sensor gets lost. Laser scanners areactive sensors. They work independent of other illumination
sources. Therefore, they can be employed under poor
illumination conditions or even in darkness. With regard to
today's technological state-of-the-art the integrated use of both
systems is an optimum choice for many applications.
A very promising and demanding application field is the photo
realistic modelling of cities. Here mobile mapping systems areneeded to gather the required 3D image data in a reasonable
time. The rough system calculations and demonstration
experiments document the feasibility. The required POS is a
key item and must work very precisely. The discussion inchapter 7.1 makes evident that different concepts are possible.
More detailed system and design calculations are necessary.
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