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The system of production of orthophotoi "on-line” or "off-line”
is another important factor which influenced the instrument
construction and profitability of orthophoto procedure# The
production line of the company decides about the orthophoto
instrumentation# When this instrumentation has to be a supple
ment of the existing photogrammetrie equipment, then simple
and unexpensive instruments working together with plotters in
"on-line" system should be chosen# But if orthophoto instru
ments can be an essential and independent equipment, then more
expentive compicated and multifunctional orthophoto devices
should be used, which in "off-line" system can be applied#
If we accept orthophoto as a document in the process of map
compilation, then we can accept also stereoorthophoto as a
technology more versatile and more universal# Therefore in
the construction assumptions of the orthophoto instruments
the aspect of simultaneous production of orthophoto and stereo
mate should be also considered#
The second factor determining the adaptation of
orthophoto instruments to the quality of orthophotomap produc
tion is connected with the assignment of produced orthophoto
graphs# In France, for instance[1,2] , orthophotos an a small
scale 1:40000 to 1:20000 are used to search of the phenomena
taking place on large regions# Orthophotos on the scale
1:20000 and 1:10000 are helpful in cartography during the
production of thematic maps in mountains areas# Orthophoto
maps on the scale 1:10000 and particularly on the scale
1:5000 are use for different purposes and, among others for
planning inventory, cartography, engineering study or prospec
ting in geology# Large scale orthophotomaps /1:2000/ are use
ful in urban planning, highways and pipelines projects, in
land inventory and land integration projects and many others#
Orthophotos can be now also used as indirect documents to line
map compilation and for x periodical map revision#
Orthophotos supplied with onomatology, counter-lines and carto
graphic net present the final form and can replace the line-
maps#
The third factor is connect eel with required accuracy
of orthophoto# The accuracy depends on:
1/ orthophotoscope construction,
2/ adjustment of the plotter and orthophoto instrument,
3/ photogrammetrie measurements v conditioned by the quality of
instruments and the operator s experience,
4/ quality of initial data and selection of photographic mate
rial and procedure#
Well performed orthophoto secures the accuracy between 0 # 1 mm
to 0,2 mm [4] • But not always such accuracy is necessary#
Recognition done by the Institut Géographique National in France
[2] indicates that nearly all orthophoto users /90%/ are safis-
fied by the 0,5 mm accuracy# The others /10$/ demand eith er isj
higher or lower accuracy# We can see that in this case it(not
diffiouli to satisfy the orthophoto receivers# In 3pite of such
low accuracy demands some users are dissatisfied with certain
degradation of orthophoto pictures in comparison with original
