Helsinki University of Technology
Abstract of Master's Thesis


About the Accuracy of Digital Elevation Modes Extracted from Digital Aerial Images

Pertti Onkalo
Helsinki University of Technology
Department of Surveying

Professorship: Photogrammetry
Supervisor: Prof. Henrik Haggrén
Instructor: Mr. Jukka Mäkelä, M.Sc.
Date: 1.6.1998
Pages: 43

In this study it is examined, what is the accuracy of digital elevation model extracted from digital aerial images. The accuracy is examined both after automatic extraction and also after interactive editing made by stereo-operator. The workflow needed for the project is described.

This study is based on two different areas. First area covers the Beltway I in Espoo and the second area covers the area between Hautaperä reservoir and Nivala. In the first study area the digital elevation model was extracted at a point density of ten meters. There are also several test areas where the used point density was five and two meters. In the second study area the digital elevation model was extracted at a point density of twenty meters and some measured breaklines and heightpoints were added in the elevation model.

The accuracy achieved was 0.05 - 0.50 meters in the first study area and 0.05 - 0.30 meters in the second area. This accuracy was achieved by method were elevation model was first extracted automatically from digital aerial images and after that edited by stereo-operator. It is obvious that if breaklines are added in elevation model the achieved accuracy is better than after automatic extraction.

The accuracy, which can be achieved, is highly dependent on the properties of the destination area. The most important property is the vegetation, which covers the area. Secondly the used point density in elevation model has a great influence in the accuracy.


Keywords Digital aerial image, digital elevation model, automatic terrain extraction, accuracy
Language: Finnish