Automation of measurements of selected targets of photopoints in application to photogrammetric reconstruction of road accidents.

Abstract

Presently, the use of photogrammetric methods in vari- ous measurement tasks is becoming more and more popular. More and more often, the achievements of photogrammetry are utilized in the reconstruction of road accidents, thus making it possible to measure the post-accident situation not only on the site but also in desk work conditions based on accident site photos. Before a photo is taken, it is necessary to target mea­surement points in a proper way. The measurement of those targets takes place most often in an automatic mode. During the reconstruction of road accidents, most often targets in the form of black and white chequered patterns, fixed at the ends of a metal cross, are used. Such targets considerably impede the measurement automation (cf. perspective distortions and scale difierences). In this paper an attempt was made at creating a program for an automatic detection and measurement of those targets. For that purpose, Matlab v. 7.10 package was applied. Due to that type of signalling, only a qualified success was attained, since target measurement needed to be supported by the pro­gram user. Also another way of signalling was proposed that enabled encoding of point numbers. Signs in the form of ring codes were selected. Algorithms of automatic detection, mea­surement and the identification of signals in digital images were developed. The created algorithms performed well under field conditions, and also allowed for the determination of de- tailed rules of making photos in accident sites.