DOI: 10.5593/sgem2012/s11.v3009


Wednesday 1 August 2012 by Libadmin2012

References: 12th International Multidisciplinary Scientific GeoConference, www.sgem.org, SGEM2012 Conference Proceedings/ ISSN 1314-2704, June 17-23, 2012, Vol. 3, 409 - 416 pp


Nowadays the digital surface model (DSM) is possible to create from a variety of data
sources. The laser scanning data rank certain to the very accurate data sources.
However, the aims of the paper are introduce another type of data that can not only
equal to the data from Lidar but in a case of using it in the applications with large scale
it can overcome Lidar data in the accuracy.
The photogrammetric procedures have been known for decades. The new technologies
make it possible to use these procedures not only for classical aerial photographs, but
also for images taken by airplane models (UAV). The contemporary software can
simulate the process of creating the cloud of the points also from the stereo-pairs. The
UAV models enable to acquire stereopair in a large scale with sufficient accuracy. Then
it is possible to use them to generate hundreds of thousands of points for a very small
area. The correct setting of the parameters for generating points by automatic
procedures is the first step in the processing of data (stereopairs) obtained by a UAV.
This includes the window size to determine the correlation, the setting of correct
correlation coefficients, the step size for sampling the image, etc.
The determination of the suitable point density for each part of modelled area is the next
step prior to the creation of the DSM. For a flatter surface is better to use fewer points,
for the more rugged parts then the denser network of the input points. This can eliminate
the data redundancy, the excessive volume of data, etc.
In the last phase is necessary to select an appropriate data model and a method for
creation the resulting DSM. The TIN model is more suitable for visualization, it can
easily adapt to different density of input points. However, the using of the resulting
model for other applications (e.g. space-time analysis of surface changes) requires
rather regular structure of the grid. In the first case it is especially necessary to select an
appropriate density data for each part of the area, in the case of using the grid then an
appropriate pixel size, interpolation method and setting of their parameters.
The process of creation the resulting DSM cannot be described as straightforward, but it
includes the repeated adjustments of the parameter settings. The aim of this paper is to
describe at the specific case study the process of the generating the surface from the
data with high accuracy and resolution (density) at the large scale model area. The
statistically evaluated results will describe the changes in the resulting DSM at various
parameter settings during the data preprocessing and processing. This will facilitate the
proper selection of the methods and settings also in other similar applications.

Keywords: UAV, stereo-pairs, point density, DSM, interpolation

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