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AVHRR model. Other types of interpolation functions include
polynomial, method of thin plate Spline and method of Rational
functions. This wide diversity of interpolation functions allows
to select the most appropriate model depending on the data
source and the available geodetic data.
The orthophoto generation process is applied to separate photos
or parts of them. In the process of ortho generation the
parameters of interpolation are important. Different methods of
image interpolation could be selected: nearest neighbour,
bilinear, cubic, sinx/x for windows sizes 8x8 or 16x16. There
are possible methods for interpolation with filtration — average,
median, gausian. The process of final othophoto generation
requires the mosaicing of orthos by cutting lines. The definition
of cut lines could be made manually by operator or
automatically based on selected criteria. Usually the cut lines
are chosen to follow the boundaries of the objects.
3.4 3-D Digitising
The digitising process requires processing in stereo
measurement mode. The predefined types of primitive objects
are usually used. It could be selected various relation between
the coordinate and attribute information. Some systems allow
definition only of graphical attributes of elements but the other
make it possible to define more complex description of attribute
information. For such systems the solution for minimum
required attribute information is important to give the user
possibility to focus mainly on coordinate information instead of
the attribute one. In this mode it is possible to digitize poins,
polylines and closed contours. The editing functions allow
inserting, deleting or moving the vertex position.
4. APPLICATION OF PCI GEOMATICS FOR URBAN
CADASTRE
The functional features of OrthoEngine allows to develop two
digital technologies for collection of digital information. The
first one is based on producing digital orthomosaic and 2D on
screen digitising with the final result the production of vector
and atribute description of objects. The table structures include
the property boundaries, street borders and building outlines.
The data are collected as set of arcs with their relation and their
properties. The structure of information in stereo digitising
mode is the same. It allows describing the objects with their
relative conjunctions. Stereo digitising mode is more reliable
then 2D digitising but require more power from the processing
computer. The data from orthophoto could be combined with
vector data for cartographic grid.
4.1 Structure of tables
Table fields at the stage of data capture are different from the
final database. Their structure is defined to ensure automatic
generation of data structure and to ensure check of topology.
They have some redundancy to ensure the check.
The fields for table for streets are shown below. The name of
graphic layer is street.
EKNM Quarter num Bound type
Uniform ID Quarter number Boundary type
Table 2. Quarter boundaries description
Atribute fields of internal boundaries are shown in table of
property boundaries. Vector layer is named Property.
EKNM Name Class Cover
Uniform ID Name of the Road class Cover type
street
Table 1. Street boundary description
Table of external boundaries has the following structure. The
vector field name is quarter.
189
EKNM Quarter num Imot num | Owner
Uniform ID Quarter Property | Owner
number number
Bound type Imot r Imot |
Boundary Right Left
type property property
ID ID
Table 3. Property boundaries
In description of adjacent polygons is used the direction of
contour tracing. In case of change the property ID the new
boundary segment is started.
Attribute fields for building description are shown in the next
table. The name of vector layer is building.
EKNM Quarter num Imot num
Uniform Quarter Property
ID number number
Owner Build type Stages ^
Owner name Building Number of
type stages
Table 4. Building description
The structure of tables allows capturing additional information
simultaneously with the process of data collection. Additional
fileds ensure verificaion of the accuracy of registered
information.
4.2 3D feature extraction
Two methods of digitising are used. First technology is based
on 3D digitising in stereo mode. The second mode uses ortho
images of the area generated by orthorectification.
Working in stereo mode generates more precised results but is
more time consuming and requires the usage of high technology
system for digital photogrammetry.
The process of data collection is separated in two stages.
Attribute information for ID, boundary type and cover type is
captured in OrthoEngine. Information about adjacency, owner
identification is defined in ArcView system. For support of this
process is used orthophoto image of the same area, produced by
orthorectification of images. Such approach helps the correct
identification of objects. The applied technique requires
entering of minimal additional information at the stage of
digitising but ensure data for additional checks of arcs and
contor identification at the stage of data conversion in the finall
data base.
The example of working window in 3D digitising mode is
shown in figure 1.
