NCJ Number
197119
Date Published
2001
Length
36 pages
Annotation
This chapter was written to explain how photographs can be used to make up for a lack of suitable measurements at collision scenes, to supplement inadequate measurements, and even substitute for measurements.
Abstract
An after-collision situation map is an easily understood display of many of the essential facts of a motor vehicle collision. This chapter discusses sources of data, quality and quantity of data, and explains how photographs can be used to make up for lack of measurements at the collision scene. Photogrammetry is defined as the use of photographs in making maps. A discussion of the principles is included, with simple drawings described as the most common form of making traffic-collision maps. Elements such as details and labeling are described. Illustrative photos and diagrams accompany the discussions. Natural perspective grids, their principle, and how to establish such a grid by plotting points are described. A square portable grid is created when measurement is not likely to be able to locate the details of an accident, and its construction is described including locating vanishing points. Also, substitutes for such a grid are described. Mathematical methods including with square grid or circular disk are described, with descriptions of coordinates, photo units, map units of measurement, the Xp axis, the Yp axis, and two grid equations are included. Also, grid refinements, reverse projection camera method, computer reverse projection, and computer aided photogrammetry are covered. A list of reference sources is included at the end of the chapter.