PROGRESSIVE SAMPLING USING TRIANGULAR INTERMESHING -
AN EFFICIENT PHOTOGRAMMETRIC DTM DATA ACQUISITION METHOD.
Ralf Bill, Franz Steidler
Wild Heerbrugg AG
ABSTRACT
This paper deals with a very economic method of Progressive Sampling
(PSA) and describes a software tool which is integrated with the
WILD AVIOLYT system software. The aim of this software module is to
describe terrain optimally with as little measuring effort as pos-
sible. In contrary to other methods of data capture, the WILD
approach is based on the use of triangles. Test profiles help the
user to define an initial capturing interval. DTM points as well as
breaklines and structurelines always forming the edges of triangles
can be used as input of the sampling procedure. The terrain is ana-
lysed and Zienkiewicz functions instead of the conventionally-used
second height differences applied, to determine whether or not
densification is necessary. Extreme values within the triangles are
also predicted by the program using Zienkiewicz functions and pro-
posed for registration. The paper describes the software module
PSA. Results with respect to the economic use of this menu-guided
tool are presented and compared to conventional data acquisition
methods.
1. DIGITAL TERRAIN MODELS AND PROGRESSIVE SAMPLING
1.1 DIGITAL TERRAIN MODELS
Digital Terrain Models are becoming more and more important in geo-
detic and photogrammetric practice. DTM's are or will be installed
in different countries, they support the planning process in many
applications, and are used in digital image processing (/1/). In
the last decade the research has concentrated mainly on the gener-
ation of DTM's more rather than on efficient methods of data cap-
ture. The conventional photogrammetric methods - i.e single point
measurement or grid measurement as static or profiles as dynamic
acquisition processes- as well as many other procedures such as
tacheometry or digitising contour sheets serve for the derivation
of the necessary threedimensional coordinates.
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