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<journal-meta>
<journal-id journal-id-type="publisher">ISPRS-Archives</journal-id>
<journal-title-group>
<journal-title>ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences</journal-title>
<abbrev-journal-title abbrev-type="publisher">ISPRS-Archives</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">2194-9034</issn>
<publisher><publisher-name>Copernicus Publications</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/isprs-archives-XLI-B1-199-2016</article-id>
<title-group>
<article-title>EFFICIENT ORIENTATION AND CALIBRATION OF LARGE AERIAL BLOCKS OF MULTI-CAMERA PLATFORMS</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Karel</surname>
<given-names>W.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Ressl</surname>
<given-names>C.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Pfeifer</surname>
<given-names>N.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Department of Geodesy and Geoinformation, TU Wien Gusshausstraße 27-29, 1040 Vienna, Austria</addr-line>
</aff>
<pub-date pub-type="epub">
<day>03</day>
<month>06</month>
<year>2016</year>
</pub-date>
<volume>XLI-B1</volume>
<fpage>199</fpage>
<lpage>204</lpage>
<permissions>
<license license-type="open-access">
<license-p/>
</license>
</permissions>
<self-uri xlink:href="https://isprs-archives.copernicus.org/articles/isprs-archives-XLI-B1-199-2016.html">This article is available from https://isprs-archives.copernicus.org/articles/isprs-archives-XLI-B1-199-2016.html</self-uri>
<self-uri xlink:href="https://isprs-archives.copernicus.org/articles/isprs-archives-XLI-B1-199-2016.pdf">The full text article is available as a PDF file from https://isprs-archives.copernicus.org/articles/isprs-archives-XLI-B1-199-2016.pdf</self-uri>
<abstract>
<p>Aerial multi-camera platforms typically incorporate a nadir-looking camera accompanied by further cameras that provide oblique views,
potentially resulting in utmost coverage, redundancy, and accuracy even on vertical surfaces. However, issues have remained unresolved
with the orientation and calibration of the resulting imagery, to two of which we present feasible solutions. First, as standard feature
point descriptors used for the automated matching of homologous points are only invariant to the geometric variations of translation,
rotation, and scale, they are not invariant to general changes in perspective. While the deviations from local 2D-similarity transforms
may be negligible for corresponding surface patches in vertical views of flat land, they become evident at vertical surfaces, and in
oblique views in general. Usage of such similarity-invariant descriptors thus limits the amount of tie points that stabilize the orientation
and calibration of oblique views and cameras. To alleviate this problem, we present the positive impact on image connectivity of using
a quasi affine-invariant descriptor. Second, no matter which hard- and software are used, at some point, the number of unknowns of
a bundle block may be too large to be handled. With multi-camera platforms, these limits are reached even sooner. Adjustment of
sub-blocks is sub-optimal, as it complicates data management, and hinders self-calibration. Simply discarding unreliable tie points of
low manifold is not an option either, because these points are needed at the block borders and in poorly textured areas. As a remedy,
we present a straight-forward method how to considerably reduce the number of tie points and hence unknowns before bundle block
adjustment, while preserving orientation and calibration quality.</p>
</abstract>
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