ICT
juality
1-wide
Aerial
photo
period
ves of
eets at
in line
ontour
al and
Xf each
1d also
gy for
precise
sult of
Z: ihe
n were
spatial
and its
ossible
her on
ection,
:gional
ch can
graphic
it scale
adastre
digital
).
ig the
IACS
em for
nn areas
NE
oses in
survey,
ed and
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
handled easily, also allows multipurpose use, we prepared the
flight plans for aerial survey at various scales. The calculations
were performed so that Hungary was placed into an imaginary
rectangle. On this basis, a comparative analytic table (Table I)
was made to help the decision-making concerning this
countrywide aerial survey campaign.
Table 1 Aerial mission planning data for decision-making
Scale of | Number of | Duration of Ground Scanning
the aerial | photograp the aerial resolution of | 21pm: one
survey hs survey (incl. the aerial picture is
(pes) turns) photographs 375 MB
in hours (in cm)
1:10 000 58 812 192 8-12 221 TB
1:20 000 14 732 96 20 - 25 SSTD
1:25 000 9338 77 25-32 345 TB
[1:30 000 | 6591 65 30-36 | 2,5TB
Note to Table 1: We performed similar analytic calculations for various
aperture before selecting the 21 um aperture for scanning, too.
After examining the economic efficiency of the aerial
photography and the photogrammetric processing, we decided
to use 1:30 000 scale for aerial survey. When using this scale —
confirmed by the data in the Table 1 — we can achieve almost
identical goals of usage, also compared to scale 1:25 000, if we
process an amount of images less by 50%.
In the year of Millennium 2000 the winning company of the
public procurement procedure, EUROSENSE Ltd. successfully
performed the aerial survey of the whole area of Hungary
within about three months and in conformity with the very
strict ,, Technical specification”, elaborated by FÓMI. (4).
The number of photographs aquisited within the programme
Aerial Survey of Hungary 2000” and handed over to FOMI for
archiving and data supply services is listed in Table 2.
Table 2 Number of photographs archived by FOMI
Number of repetitions All Digital | Colour
projec | images slides
ES 25 3% [4%] tion pes pes
centre
Number of
projection | 5884 719 32 | 7 | 6642
centres
Including 5884 | 1438 | 96 | 2 7446
| repetitions 8
Handed
over to 6667 7446
FÔMI
2. Producing Digital Orthophotos
The technology of producing digital orthophotos can be shown
in three main steps (5), (see figure):
Step I. Determining the absolute orientation elements of
the images by aerial triangulation using bundle adjustment.
Step I. Producing the digital elevation model (DEM).
Step III. Production of digital orthophoto by simultaneous
use of data determined in Steps 1. and 2. and transforming
the image elements pixel by pixel.
Beyond the use of high-tech technologic instruments and
keeping strict technological discipline, significant amount of
Work time and costs are necessary to perform all these.
Therefore, when carrying out this countrywide job, a uniform
technology should be applied, which
* Provides the maximum accuracy, which can
economically be achieved from the given aerial
photographs;
377
e Considers the opportunities offered both by
traditional and up-to-date ^ photogrammetric
procedures;
e Is optimal in duration, beyond its cost-efficient,
economical technical solution;
e Is built on the national databases developed by FÓMI
during several decades and representing significant
value;
* Provides the uniform quality and accuracy of the
digital orthophotos, wherever they were produced;
e Provides the state acceptance of the orthophotos with
a certificate guaranteeing their quality;
e Supports the development of metadatabase needed for
further marketing and archiving;
e Serves as a basis for the revision of the EOV
topographic maps at scale 1:10 000 and the start of
the Hungarian Topographic Programme.
Figure 1: Main steps of producing orthophotos
Image
Tc
Tn
'h B
: Ji Ta
D, ! C
! Map
surface
A’g Bg Cy
2.1. Aerial Triangulation
The development of the fourth order geodetic triangulation
network of Hungary started in mid seventies and was finished
by 1992. In accordance with the specifications, the density of
the fourth order points is 1 point/2 km^ in rural areas, while
denser in the built-up areas, i.e. less than 1 point/l km“ The
accuracy of the fourth order network is very good: + 3-4 cm.
The network is built on the points of the higher order
triangulation network, so it forms a counfrywide uniform
geometric basis.
When realizing MADOP, it was advisable to match the blocks
of aerotriangulations to those points. The accuracy of the fourth
order points is much better than the accuracy values, which can
be achieved from aerial images at scale 1:30 000, so they serve
as a reliable basis for geometric matching of the aerial
triangulation blocks. As a result of the aerotriangulation block
adjustment, we have got the orientation parameters of the
individual aerial photographs (see the figure, step 1), which
enable us to fit the aerial photographs into the national
geodetic control network within the error limit of the aerial
triangulation. The accuracy of the orientation parameters of the
aerial photographs and the reliability of the DEM together will
determine the accuracy of the digital orthoimages to be
produced, i.e. the accuracy of the matching into the national
geodetic control network.
