Automatic generation of elevation data over Danish landscape

Automatic generation of elevation data
Chapter 3: Experiences with Match-T and the investigation strategy
A source study of other people’s investigations and experiences with Match-T is described. Investigations
with Match-T have shown that different parameters can influence the result of automatic generation of
elevations from digital images, for instance, the scale of the images, their resolution, the mesh size and
the landscape type. On the background of this source study, the investigation strategy of the project is established.
Chapter 4: The data material
A test area is chosen south of Aalborg University. The area is chosen because of its varied terrain and its
location close to the university. The area includes open, flat and hilly fields, woods, a residential
neighbourhood (suburb), and gravel pits with steep slopes. This small test area represents a broad segment
of the kind of landscape types found in Denmark. At the start of this thesis digital cameras did not
exist, therefore the area was photographed in three scales, and the images have been scanned in three
different resolutions. Further, a description is given of the establishment of the frame of reference for the
quality control of the individual tests. The frame of reference consists of elevations that are measured with
superior accuracy. Appendix B includes a detailed description of the establishment of the frame of reference,
Chapter 4 is a brief summary of this.
Chapter 5: Preparation for grid generation
As preparation for the elevation determination, Match-T is configured. The parameters used are discussed.
Chapter 6: Pre-analysis of the generated grids
Match-T’s own modules for the indication of problems with the individual grid points in the automatically
generated grids are investigated. Also, a superior evaluation of the completeness of the automatically
generated grids is carried out.
Chapter 7: The investigation
The evaluation and analysis of the results from the individual calculations have been done step by step.
The first step is a simple determination of the elevation difference between the calculated results and the
frame of reference. Another comparison is done after elimination of gross errors. It has been investigated
whether the scale, resolution, mesh size and landscape type of the images have had any influence. Possible
gross errors have been localised and analysed.
Chapter 8: Results on the basis of Chapter 7
The experiences gained in Chapter 7 are summarised and finalised. Then an elevation model of the test
area is generated, where the experiences with the method and the influence of the Danish landscape on
the results are discussed, and the accuracy is evaluated. The possibility of eliminating possible gross errors
by combining data obtained by the different resolutions has been attempted.
Chapter 9: Theory and practice
After the analysis of the results, these have been held up to the theory and experience of others. How do
theory and practice compare? Where and why are results obtained that do not correspond to the theory?
On the basis of the investigations carried out, possible improvements are discussed, and a method for
automatic data collection in Denmark is recommended.
Chapter 10: Conclusion and perspectives
The suitability of the automatic correlation method is evaluated in relation to the determination of a nationwide
terrain model of Denmark. Furthermore, potential future studies based on the project are discussed.
This thesis also includes an appendix in four parts, A, B, C and D:
� A Correlation techniques
� B The data material
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