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compare them in order to assess the statistical validity
and crosscheck the accuracy of the both types of data.
- Laser scanning data are much more informative due
to their ‘natural three-dimensionality’, that is they
allow the morphology of the scene to be presented in
greater detail, using automatic and semi-automatic
methods among others. Yet:
- In most cases, the use of aerial photography data and
the methods of digital photogrammetry for their
processing allow a better accuracy of geopositioning
and geometric measurements as compared to the
‘pure’ laser detection and ranging. Therefore the
application of these two types of data in combination
will result in improved geodetic accuracy of laser
data. As of today, the accuracy of laser data is within
15-20. em, which is insufficient for a number of
important applications.
2. TECHNOLOGICAL BACKGROUND
Data obtaining capabilities of airborne survey equipment,
laser scanners and digital cameras in particular, have been
enhanced significantly in recent times.
Thus, the last model from OPTECH Inc., ALTM3100 laser
scanner, has a pulse frequency of 100 kHz and is capable of
recording returns from each pulse emitted. This ensures a
scanning density of up to 10 laser points per a square meter
of the ground surface. At the same time, digital frame
cameras with large arrays have become commercially
available. Thus, an ULTRA CAM model from VEXCEL
generates images of 11500 by 7500 pixels and offers a
frame rate of 1.3 Hz.
Such sophisticated data obtaining capabilities of modern
airborne survey equipment create a favorable background
for further improvement of algorithms aimed at the
integration of laser scanning and aerial photography data
because a high degree of detail provided by both types of
data (density of laser points and high resolution of aerial
photographs) allows the use of analytical methods for the
purpose of integration rather than heuristic methods as it
used to be.
3. GEOKOSMOS HISTORY
Geokosmos is a privately owned and operated Moscow-
based topographical and surveying company established in
1993 in Moscow. The company is reputed as a significant
player on the Russian topographic and geodetic survey
market, making use of digital land and aerial surveying
technologies as well as 3D digital multipurpose modelling.
Geokosmos focuses on three main lines of business: the
provision of professional surveying services using laser
scanning technologies, development of its own software
products for various surveying applications and consulting
and development of integrated laser scanning technologies.
In 2001 Geokosmos successfully carried out the first
Russian large-scale project involving the use of an aerial
laser scanner for large-topographic survey and creation of a
3D digital area model of over 340 sq km for a railway
design based on the scanning results. It continued studying
ground-based scanning systems, actively co-operating with
producers and users, and a successful record of using these
technologies resulted in further projects.
The company has at its disposal two aerial laser scanners:
Optech ALTM-2050 & ALTM-3100 with 50 and 70 kHz
scanning frequencies and a significant number of Trimble
GPS receivers, ProXR, tacheometers and ground-based
laser scanners.
177
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B2. Istanbul 2004
The company employs a full-time staff of more then ninety
specialists: highly skilled, creative, young personnel within
a strongly organised structure. In October 2002, an aerial
surveying division was established. The new division is
fully staffed with highly qualified graduate specialists
having extensive experience and an impressive record of
the application of airborne laser scanning systems both
within Russia an in many other European and Latin
American countries. Aerial laser scanning has since
become a key line in the company's activity.
At present Geokosmos clients include major Russian
companies, such as OAO Gazprom, RAO UES,
MOSAVTODOR and many others. Each of these is ranked
high in its respective area. OAO Gazprom holds a huge
monopoly in the Russian gas industry, which provides 25
per cent of the national income. All Russian energy
resources belong to RAO UES, the biggest Russian power-
engineering company, which owns more than 370,000 km
of power lines.
4. ADVANTAGES OF LASER SCANNING
Considering the application of the laser scanning method, a
number of significant advantages can be mentioned that are
provided by this method in contrast to other traditional
approaches.
- The efficiency of laser scanning is extremely high. A
milestone of 500-600 km has been reached in practice
during one day of aerial survey. It should be noted
that the post-processing of survey data obtained using
the laser scanning method normally takes as much
time as the aerial survey itself, which allows survey
data to be processed immediately in the field. In its
turn it makes it possible to efficiently control the
quality of survey data and redo survey work where
necessary. It is obvious that laser scanning surpasses
other traditional methods of aerial survey in
performance, as those methods require intricate and
time-consuming data post-processing.
- Laser scanning does not require compilation survey
for aerial survey data on the ground. The need to
perform such operations may cause a serious problem
for traditional survey methods, especially in remote
and hard-to-reach areas.
- . Traditional stereophotogrammetric methods, whether
analytical or digital, ensure that scene components are
measured with a high degree of accuracy. However,
these methods do not allow the automatic
reproduction of the shape of complex engineering
facilities. Besides, the spatial location of wires and
ropes makes it extremely difficult to apply
stereophotogrammetric methods to measure sags,
clearances and coordinates of suspension points, thus
resulting in an unsatisfactory accuracy of such
measurements. Since laser detection and ranging
allows all components of the scene to be measured
directly, it is absolutely free of the above constraints.
Moreover, the computer-aided processing of primary
laser data permits a very high accuracy of the above-
mentioned parameters, for instance, sags can be
measured with an accuracy of 5 to 7 cm. At the same
time, the laser scanning method always generates a
3D image of the object, ‘a cloud’ of laser points
reflected from the surface of the object. The cloud
itself considerably facilitates the visual analysis of the
object’s shape and allows all primary geometric
measurements to be taken with a standard level of
accuracy offered by the method, i.e. 15-20 em. It is
