International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. [stanbul 2004
since their number is reduced. Reliability can be increased by
applying the following principles:
e Additional linear and angular measurement from
another surveying point should be made, whenever it
Is possible;
e Selection of pairs and groups of control points which
fulfill certain geometrical conditions (lies in the same
horizontal or vertical line, the same depth plane of
facade, etc) should be made.
5.10 Exterior orientation of images
Exterior orientation is done by standard simultaneous procedure
of bundle adjustment. Elements of exterior orientation are
pertaining to the object coordinate system (Xt, Yt, Zt at Figure
5). Input data for bundle adjustment are field coordinates of
control points, interior orientation data of camera and measured
image coordinates of control and tie points. Measurements are
performed using rectified photogrammetric images and
appropriate software. Output results of this procedure are
elements of exterior orientation of all images include in the
block of perspective bundles. These elements are necessary for
the next phase regarding facade's digital orthophoto production.
There are two more reasons why bundle adjustment should be
done following the suggested procedure. First, elements of
exterior orientation will become part of archive technical
documentation, so they will represent starting point for further
works at any time. Since that moment isn't limited in terms of
time, the importance of bundle triangulation lays also in the fact
that accuracy and reliability of control points is simultaneously
verified by the triangulation. Therefore, continuation of works
brings no risks, no matter when or for what purpose it should be
initiated.
5.11 Digital orthophoto production
Digital orthophoto production of object is suggested as standard
procedure in the first phase of technical documentation
production. Namely, there is one essentially huge step in
between bundle adjustment and orthophoto production —
creation of digital elevation model (DEM). As it is very often
the case of having objects with regular geometric shapes, DEM
can be simplified and approximated with mean vertical planes
representing object’s facades. Errors of digital orthophoto
caused by such a simplification occur just at those points that
stick out from mean plane and these errors grow from nadir
towards peripheral image parts. However, since digital
orthophoto, as seen from the suggested procedure’s point of
view, serves as preliminary geometric ?background? for
perceiving object geometry, it is justified to produce it in a
proposed way.
RAHCRH AROPM HATACA 5 VOIERE RAHA TOADEK MAZALCRA
: Werne c fosa f
Cursgans: arvcr 2x02 Pet RO Waday 1 MF ME:
fttaAnt ap DOO 4s
Figure 7: Printed form of digital orthophoto
Digital orthophoto might be represented also in printed form, in
appropriate scale (Figure 7). Nevertheless, the suggested
procedure does not anticipate this as a compulsory step, because
expenses get higher and problem of archiving printed material
arise (in addition, it is redundant with already archived digital
content).
5.12 Technical report
Technical report represents usual form of engineering statement
about the most important elements of conducted works. It
consists of three elements: general part, textual part and
supplements. General part contains information about
organization and persons participating realization and technical
control of works. Textual part of technical report has general
information about object of cultural heritage, workflow and
achieved results. Supplements of technical report should have
the following elements:
e object disposition sketch with marked positions of
camera during image capturing,
e catalogue of all control points with belonging
descriptions,
e data about surveying calculations for control points
coordinate determinations,
e data about the camera,
e data about image geometric rectification, with proof of
achieved accuracy,
e report about results of bundle adjustment, with proof
of achieved accuracy and reliability,
e adjusted elements of exterior orientation.
Suggested procedure assumes technical report in digital form.
Recommended document format is Acrobat PDF.
5.13 Archiving
Final step of the first phase in production of technical
documenatation is archiving. Digital archive content is the
following:
® rectified images in TIFF format,
e digital orthophoto in georeferenced TIFF format, and
e technical report in PDF format
The following remarks could be made regarding archive
memory requirements:
e Memory capacity for archiving one image (6x6cm,
1600 dpi, full color) 1s 42Mb;
e Memory capacity for archiving technical report
depends on number and quality of images used.
Recommended is JPG format, in resolution not higher
than 400 dpi in printed A4 form;
e Memory capacity for archiving digital ortophoto
depends on number and the size of TIFF files.
Archiving represents logical end of the first phase in production
of technical documentation for cultural heritage. Such
documentation becomes part of archive that should be kept
within responsible institution for cultural heritage.
Nevertheless, very soon this kind of documentation will find à
way to serve for certain information systems on cultural heritage
or it will urge application of IT technology for protection of
cultural heritage.
Intern
THEE IE
In spi
area (
object
is no
photo;
of ph
palette
this w
duty.
this |
produ
cultur
digita
The €
initial
hardw
neces
photo
mass
objec
produ
docur
comp
geom
discu
neede
analy
very
produ
docur
and ?
Barat
Di git
In: 7
Sensi
Neth:
Bartc
B. ;
herit:
Rene
Neth
Bocc
archi
Arch
Infor
Part |
Chor
Luth
A.B.
of |
Surv
Dorf
Toz,
worl
Phot
