The Accuracy of Digital Models for Road Design - Geoinformatics for Intelligent Transportation - page 235

level in form of 3D contour lines as a part of the Fundamental Base of Geographic
Data of the Czech Republic (ZABAGED). Furthermore, the Digital Relief Model
(DMR) can be used in DMR1 to DMR5 versions. The latest versions feature
utilization of aerial laser scanning. By 2016, a model with regular 5 m grid will be
available in the whole CR territory. However the accuracy, because of the RMSE
h = 0.18 m [ 1 ] will only be suitable for study of the road run and its variants. For
subsequent designing works more precise elevation data must be obtained.
The entire documentation of all stages of the road construction is elaborated in the
Baltic system after adjustment and in the national S-JTSK datum. The geodetic,
photogrammetric and laser scanning serve for obtaining quality input data for
designing documentation elaboration. The data enable to incorporate the construction
variants into the territory of interest. Required accuracy and size of the territory of
interest are the decisive factors for selecting a suitable method for the material
elaboration. One of the most important source data, on which quality depends
majority of control surveying during the designing works and during the construction
itself, are the elevation data in the future construction area as well as in the area of
future borrow-pits and other construction manipulation areas. If the natural terrain is
not surveyed precisely, the assessment of suggested road variants is very uncertain
and simulation of vehicle movement on thus variants is not suf

ciently evidential. All
subsequent calculations will be uncertain since there would not be a first-quality

origin, from which the drawn/thrown up material could be calculated and which
would enable to compare the current state with the designed one [ 2 ]. Following
methods seem to be suitable for suf ciently precise digital terrain model:

(a) Methods of aerial photogrammetry and stereoscopic mapping of aerial pho-
tographs. The resulting material for the road variant study as well as for
subsequent designing works is a set of digital planimetry and altimetry files of

a special-purpose map. The RMSE accuracy of the altimetry derived by
photogrammetry-stereoscopic method is h = 0.045 m for the ground sample
distance of the aerial photographs equal 0.035 m, see e.g. [ 3 ].
(b) Methods of aerial laser scanning for creating a digital model needed for
designing activity (after selecting and approving the appropriate variant)
enable to obtain (after the flight and primary data processing) very dense and

precise digital terrain model. The laser scanning apparatus usually emits one
light beam and receives it back (after its re

fl

ection from the terrain) divided up
to eight so called echoes. Information recorded for the

fl

ection
of the beam is used for evaluation of planimetry and altimetry information on
the terrain. Such determined Digital Surface Model contains all terrain
obstacles. The model is further adjusted with special algorithms and calibrated
onto map control points surveyed in the terrain. After subsequent result
adjustment and necessary

first and last re fl

filtrations of the terrain objects, the DTM of the
particular area is obtained with density up to 12 points per m 2 (in open terrain)
with RMSE h = 0.03 m (Fig. 1 ).
(c) Methods of terrestrial mobile laser scanning for production of precise 3D
digital terrain model utilized during designing works are based on an apparatus