IX-B4, 2012
1 othophotos (not
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2002, Wang 2004,
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decided to develop
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stereo orthophoto,
as a plugin in
Il be written using
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with orthoimage
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Optionally DTM
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During compilation
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could assume that
ild application 10
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
Assumption b) implies that data have to be previously prepared,
outside of QuantumGIS environment. Certainly this is
significant obstacle for an user, who has to order preparation of
stereo component from orthophoto supplier (there is a module
for generating stereo component in some photogrammetric
software like Erdas or SocetSet). On the other hand there is no
justification for need to create stereo ortophoto from aerial
photographs in QuantumGIS itself. Considering this, user
would have to know photogrammetric production line, and this
contradicts popularisation of stereo visualisation among large
number of recipients of GIS, which we are after. Besides, for
that to happen user would need photographs along with
orientation. elements. Knowing that preparation of stereo
components isn't significant increase of effort in comparison to
standard orthophoto creation procedure, one could hope that in
short amount of time adequate data will surface provided by
internet GIS oriented sites using WMS technology. Obviously
WMS can be used as standard facility for providing anaglyph
images. Therefore there are grounds for assumption that user
would have access to stereo data without any special effort on
his part. Such futuristic solution blend itself well into
prerequisites of popularisation of stereo orthophoto among wide
circle of GIS recipients presented in chapter 3.
Sterco orthophoto flaw as shown in chapter 2 , namely
distortion of height for vertical objects located in mountainous
areas, can be corrected during measurement by introducing
adjustments calculated from DTM. That is why such
functionality is to be optionally included in developed
application, and it is the reason why it was pointed out in
assumption b) as a component of input data.
Currently prototype application is being developed. As an
intermediate solution on the way to achieve our goal
stercoscopy tests are limited to vertical objects, or employing
residual parallax between two orthoimages generated from
adjacent photographs. Figure 3 shows such an anaglyph pair
operated in QuantumGIS.
G Quantum GIS1.7.1-Wroclaw
Pk Edvcja Widok \Warstwa Ustawienia Wtyczk — Wektor Raster Pomoc
© e »
Fig. 3. Example visualisation of stereo orthophoto in
QuantumGIS environment (courtesy of MGGP AERO
Company, Tarnow, Poland).
5. CONCLUSIONS
The prospect of stereo orthophoto technique renaissance is very
promising, especially now in the era of digital photogrammetry
and advanced GIS development. In many countries, including
EU members, the governmental photogrammetry projects are
regularly conducted for cultivation control purposes, producing
valuable sets of data. By using this existing data the
stereoscopic pairs could be created with relatively little effort.
The best way of stereo orthophoto popularization is GIS — the
means of reaching out to wide variety of users.
Stereo orthophoto does not compete with 3D vector models,
since it is a totally different product, with a lot of advantages
but also a few flaws. Stereo orthophoto should be perceived as
a supplement of othophoto — so well adapted by geoinformation
community.If users accepted orthophoto's visual model of
reality, they should also accept the opportunity of seeing and
exploring this model in 3D. One of the most important
advantage of the stereo orthophoto product is its metrics,
although slightly lower than obtain from classical
photogrammetric models, but enough for many GIS tasks. The
significant accuracy decrease, pointed in some publications (Li
et al 2002, Wang 2004), of stereo orthophotos compared to
classical photogrammetric models has not been confirmed
during authors' research on photogrammetric data of digital
camera images. Worth mentioning is the advantage of using
digital camera with quite narrow field of view in mountainous
areas due to minimization of the residual parallax distortion.
Moreover, there is the possibility of compensating this
deformations, which will be one of the option in created
application.
An essential condition for popularization of the stereo
orthophoto is for geoportals to publish relevant data. Currently
public and commercial geoportals offer only an orthophoto
mosaics. However there is the potential for similar mosaics
generation from stereo components. Production cost of such
data is significantly lower than production of 3D, textured
models - currently provided by a several commercial geoportals.
REFERENCES
Baltsavias E.P., 1996. Digital ortho-images — a powerful tool
for the extraction of spatial- and gco-information. ISPRS
Journal of Photogrammetry and Remote Sensing ,Vol. 51, Issue
2, pp. 63-77.
Blachut, TJ., 1971. Mapping and Photointerpretation System
Based on Stereo-Orthophotos. ETH Zurich.
Blachut, T.J., 1976. The Stereo-Orthophoto Technique in
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and Remote Sensing, 42(12), pp.1511-1519.
Chang H., Yu K., Joo H., Kim Y., Kim H., Choi J., Han D.Y., Eo
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