AUTOMATIC PRODUCTION OF DTM DATA BY DIGITAL OFF-LINE
TECHNIQUE
B. Makarovic
Photogrammetric Dept., ITC, The Netherlands
Commission II, Working Group II-2
ABSTRACT
A review is presented of the state of the art in digital off-line
technique for production of DTMs. Outlined are the main process
stages, their interactions, and operations involved. Data structure,
strategy, algorithms, and techniques of image matching are strongly
interrelated. Performance can be improved by optimising the overall
process and by carrying out some pre- and post-processing operations
interactively with human. Moreover, use can be made of multiple sets
of image data, multi-stage strategy, external data, and of collect-
ive processing.
I. INTRODUCTION
The objective is to present an overview of the state-of-the-art and
thus new developments in automation of digital terrain modelling by
using off-line (or time-delayed) techniques. The intense and diver-
sified developments make a comprehensive review in a short paper
virtually impossible. Nevertheless, an attempt will be made to out-
line, discuss, and orderly structure the information.
Because of various restrictions, the contents are compressed and
simplified. First some general issues are reviewed, concerning the
automatic off-line systems. Then a description is given of the main
process stages, i.e. pre-processing, image matching, and post-pro-
cessing. Each of these is supplemented by a list of the correspond-
ing development trends.
II. GENERAL
Consideration should first be given to the evolution and general
trends in automation in photogrammetry, definition of the overall
photogrammetric process, the main stages of automatic restitution
and corresponding interactions, types of data, problems originating
in input images, and properties of on-line versus off-line automatic
systems.
l. Evolution
The first photogrammetric automated systems (analogue, hybrid and
all-digital) were developed in the period 1958-1962. Until 1968,
electronic analogue systems dominated and then emphasis was gradual-
ly shifted to hybrid systems. Since 1976, however, a transition has
taken place to all-digital systems, operating both in real-time and
332