NCJ Number
7026
Date Published
1972
Length
11 pages
Annotation
TECHNIQUE TO ENABLE POLICE INVESTIGATORS TAKING PHOTOS OF THE SCENE OF AN ACCIDENT OR CRIME TO INCORPORATE A GRID FROM WHICH A MAP CAN BE DRAWN.
Abstract
INVESTIGATION OF AN ACCIDENT OR CRIME MAY REQUIRE PHOTOGRAPHS AND A MAP OF THE SCENE. ADEQUATE PHOTOGRAPHS POSE NO PROBLEM SINCE THEY CAN BE TAKEN QUICKLY BUT OBTAINING MEASUREMENTS FOR A MAP IS A MORE TIME CONSUMING AND TEDIOUS TASK. SPECIALLY DESIGNED CAMERAS FOR PHOTOGRAPHIC MAPPING ARE EXPENSIVE AND NOT GENERALLY AVAILABLE. A SIMPLE SOLUTION IS TO MAKE PHOTOGRAPHS FROM WHICH MAPS CAN BE DRAWN IF AND WHEN THEY ARE NEEDED. THE PRINCIPLE IS SIMPLE - IF THE SUBJECT TO BE MAPPED IS ON A FLAT FLOOR OR PAVEMENT, A PERSPECTIVE GRID, (I.E.,A RECTANGLE OF KNOWN SIZE), CAN BE SHOWN ON THAT SURFACE IN THE PICTURE. THIS SERVES THE DUAL PURPOSE OF ESTABLISHING A SCALE AND PROVIDING REFERENCE POINTS FROM WHICH A MAP CAN BE DRAWN. WITH THE RECTANGLE AS A BASE, AN APPLICATION OF THE PRINCIPLES OF PERSPECTIVE WILL ENABLE A DRAFTSMAN TO PRODUCE AN ACCURATE MAP. THIS HANDBOOK PROVIDES SIMPLE, YET DETAILED GUIDELINES FOR THE CONSTRUCTION AND USE OF THE PERSPECTIVE GRID PLUS PROCEDURES FOR DRAWING A MAP FROM PHOTOGRAPHS SHOWING THE GRID. THE MANY PHOTOGRAPHS AND DIAGRAMS ILLUSTRATING THE PRINCIPLES INVOLVED IN USING PERSPECTIVE GRIDS MAKE THIS TIME SAVING TECHNIQUE EASILY ADAPTABLE BY POLICE INVESTIGATORS.